Radio Boulevard  -  Western Historic Radio Museum


Vintage Longwave Receivers

Restoration and Performance Testing the Following Longwave Receivers

IP-501-A - Radiomarine Corp. of America - 1923  ~

  Type 105-A - Mackay Radio & Telegraph Co. - 1932  ~

RIO  -  National Co.,Inc.  -  1933  ~

~ RAA-3  -  RCA Manufacturing Co.,Inc.  -  1935  ~

 ~   RAZ-1, CRM-46092 - Radiomarine Corp. of America - 1941  ~

    RAK-7, CND-46155 - RCA-Andrea Radio Co. - 1944  ~

BC-344-D - Farnsworth Television and Radio Corp. - 1944  ~

AR-8510 - Radiomarine Corp. of America - 1944  ~

RBL-5, CNA-46161-B - National Co., Inc. - 1945  ~

RBA-1, CFT-46154, RBA-6 CFT-46300 - RCA-Federal Tele.&Radio Corp - 1941-45  ~  

  Type 3001-A - Mackay Radio & Telegraph Co. - 1948  ~

R-389/URR - Collins Radio Co. - 1951  ~

~   SP-600VLF-31 - Hammarlund Mfg Co., Inc.- 1955  ~

What to Listen to on LW, Loop Antennas, LW Stations, VLF Stations

Operating Vintage Gear on the 630M (472-9 khz) Band with Log incl'd

USCG  Loran C Master Station"M"- Fallon, Nevada - 2007 Photo Tour 

NBD Stations in Nevada  &  NDB Station Log

by: Henry Rogers WA7YBS

photo above
: These massive towers dwarf the two-story station house in the foreground. This is the VLF station at Arlington. The photo is from the early-1920s when Arlington's time signals were on VLF.    photo from: Radio Broadcast 1922

"Longwave" is an unofficial but commonly used term that refers to all frequencies below the AM BC band. These frequencies are properly known as Medium Wave (MW, 300kc to 3000kc,) Low Frequency (LF, 300kc to 30kc) and Very Low Frequency (VLF, 30kc to 10kc.) A Long Wave Receiver would be a receiver specifically designed for a frequency coverage of approximately 600kc down to 15kc but also can be any receiver that was specifically designed for LW reception but with limited frequency coverage.


Vintage Longwave Receivers

Performance Testing Classic Vintage Longwave Receivers


Radiomarine Corporation of America
(Wireless Specialty Apparatus)


IP-501-A - MW & LF Receiver-Amplifier

Commercial Shipboard Receiver from 1923

40kc  to  1000kc


"Listening on longwave with a 1923, battery operated, regenerative receiver? You gotta be kidding!"

One has to remember, the IP-501-A was the commercial shipboard receiver that was built to the highest standards of the day. It was well-known for its superior performance and reliability. It is the "R-390" of the 1920s.

The initial versions of this receiver were built at Wireless Specialty Apparatus, a company that was part of the cross-licensing "Radio Group" headed by General Electric and included Westinghouse, AT&T, RCA and the United Fruit Company (who owned Wireless Specialty Apparatus (WSA.) WSA built a few broadcast radios for RCA in 1921 and 1922 but by 1923 they had become part of RCA. Soon WSA became Radiomarine Corporation of America and was building shipboard radio gear for RCA.

This three tube receiver uses a three-circuit tuner with a regenerative detector and two transformer coupled audio frequency amplifier stages - not exactly unheard of for a lot of radio receivers in 1923. What really sets the IP-501-A apart from the other three-circuit tuner regen sets is its incredible Antenna Tuner section that is entirely shielded from the main part of the receiver (which is also entirely shielded.) The Antenna Tuner allows exact tuning of the antenna's impedance so the load remains the same on the Secondary circuit. It's like having a built-in pre-selector. The only transference of signal happens by way of the small variable coupling coil located inside the Antenna coil. The fact that the receiver cabinet and front panel are entirely shielded results in no hand-capacity effects when the receiver is operated as an autodyne detector. This makes tuning CW super-easy. The Secondary Tuner has six frequency ranges from 1000kc down to 40kc and the dial is calibrated in meters. The Tickler coil is actually a variometer built into the Secondary coil form and includes load windings from the Secondary inductance to improve regeneration on the lower frequencies. The audio amplifier section is standard and uses two RCA interstage transformers. The audio gain is more-or-less controlled by the filament voltage and the operator can also select how much gain is required by using one of the phone jack outputs. The phone jacks also control the filament voltage to the tubes and only the tubes needed are in operation when that jack is selected. Maximum audio is from the AF2 jack which provides Det + 2 AF stages. In high noise level conditions or for very loud signals, AF1 saves the operator's ears by using just one audio amplifier. If the DET jack is used, only the detector tube is in operation - this would be for receiving local transmissions. Intended audio output is to Hi-Z earphones but the IP-501-A will drive a horn speaker loudly from the AF2 jack. To power the receiver up requires 6vdc at .75A for the filaments, 45vdc and 90vdc for the B+ requirements and -4.5 for C bias. The filament adjustment pot controls the A battery into the receiver and is used to turn off the receiver. Pulling the phone plug from one of the jacks will turn off the tubes but the meter will still show A battery voltage unless the filament pot is turned off. The tubes normally used in the IP-501-A were UX/UV-201A triodes. Operating any radio receiver that uses batteries for its power source can be a hassle and expensive unless you are all ready set-up to run battery receivers. Usually highly-filtered power supplies provide "close to pure" DC voltages to operate these types of receivers. I use a Lambda 6vdc 4A power supply for the A supply, a 1920s RCA Rectron B Eliminator for the B supply and a 4.5vdc battery for the C bias. Hi-Z earphones are necessary for the audio output and I generally us a set of 2200 ohms dc, Western Electric 518W 'phones. The IP-501-A also requires a fairly large antenna worked against a true earth ground for best performance.

photo above: Inside the IP-501-A receiver showing the high quality construction

 In operation, the filaments are set to about 4.5 to 5.0vdc using the panel meter as reference. Tuning is accomplished with the Secondary Condenser and then "peaking" the signal with the Antenna Condenser. Sensitivity is controlled by use of the Tickler. Since an adjustable resonance and load can be controlled by the Antenna Condenser control, the Tickler control can be set to one position and doesn't require too much adjustment per each tuning range. Selectivity is controlled by the Coupling control. Changing the settings of any of the controls will always cause an interaction in any regen set when it is used as an Autodyne Detector (oscillating regenerative detector.) When the IP-501-A is used as a three-circuit tuner with Autodyne Detector, the Coupling control must be set to "Critical Coupling" for best performance. This requires the operator to tune through the Antenna Condenser's resonance while listening for a "double-click" (and for the oscillating to stop.) If the clicks are heard, this indicates too much coupling. Continue to loosen the coupling and retune the Antenna Condenser until no clicks are heard at resonance. Now the Coupling is set properly. Large changes in tuned frequency will require minor adjustments to the Coupling setting. All tuning can usually be accomplished using just the Secondary Condenser control for tuning stations and then using the Antenna Condenser for adjusting the signal to maximum. Now and again you will have to slightly re-adjust the Tickler. For tuning in NDBs, the IP-501-A should be operated as an Autodyne Detector receiver. This provides a heterodyne so the NDB carrier can be easily heard. Regenerative detectors can become unstable at the oscillation point and good construction helps to stabilize the regeneration. The IP-501-A is very stable and easy to operate in the Autodyne set-up since that was one of its intended uses - to copy the CW from arc transmitters.

 I have had this IP-501-A since 1979. A ham friend sold it to me after he had traded a telephone pole for it. I have performed three restorations on the set over the years. The last one in 1984 brought the IP-501A back to full original configuration and appearance internally and very good restored condition externally. I used the receiver back in the 1980s with a 125' EFW antenna and tuned in all the normal AM BC stations one would expect. As far as Airport Non-Directional Beacons (NDB,) the only one I remember tuning in was SPK 251kc, located at the old Reno-Cannon AP. I remember SPK because they used to transmit voice weather with the MCW ID "SPK" in the background. I really didn't know how to get a lot of performance out of the IP-501-A back then. The AM BC performance was fine but listening to AM BC over a horn speaker gets boring after awhile. When I opened the museum in 1994, the IP-501-A was installed in a display case and it stayed in the case for almost 15 years. Lately, I had been thinking about trying something different, as a challenge to the performance capabilities of early regenerative receivers. Since the IP-501-A was the commercial receiver of choice in difficult environments and it had every indication of being the "best" of its day, I decided to give it a try. I used my ham antenna, a 135' tuned dipole, but with the feedline shorted. This would provide a vertical with large capacity hat configuration similar to the large "T" antennas of the twenties. Our initial tests turned up a small problem with the IP-501-A's circuit selector switch. We had no detector plate voltage but it was just a bad contact that needed a bit of cleaning and we were up and operating,...sort of. Lack of audio output was another easy fix. The bias SS power supply had failed and was at -25vdc, definitely in the cut-off region for UX-201As! I sub'd a battery for the bias and then the IP-501-A sprang to life. Before power-up, I had tuned the receiver to around 800 meters as a pre-set and, to my complete surprise, SX 367kc in Cranbrook, BC, Canada was coming in (this was at about 5PM local time in December.) I tuned in a few more NDBs and then decided to wait until about 10PM and try again. At 10PM, I received around 25 more NDBs tuning from 326kc up to 414kc. Best DX was the 2KW transatlantic beacon DDP 391kc in San Juan, Puerto Rico. 

IP-501-A NDB Log - 2009 - The following is the log of the NDBs copied using just the IP-501-A receiver and the 135' tuned dipole antenna with the feedline shorted. NDB location, frequency and power (if know) are listed. Total was 103 NDBs copied in a three-week period in January 2009.
AA - 365kc - Fargo, ND - 100W
AEC - 209kc - Base Camp, NV
AOP - 290kc - Rock Springs, WY
AP - 260kc - Denver, CO - 100W
AZC - 403kc - Colorado City, AZ
BKU - 344kc - Baker, MT - 80W
BO- 359kc - Bosie, ID - 400W
CII - 269kc - Choteau, MT - 50W
CNP - 383kc - Chappell, NE - 25W
CSB - 389kc - Cambridge, NE - 25W*
CVP - 335kc - St. Helena, MT - 150W
DC - 326kc - Princeton, BC, CAN
DDP - 391kc - San Juan, Puerto Rico - 2KW
DPG - 284kc - Dugway Proving Gnds, UT
DQ - 394kc - Dawson Creek, BC, CAN
EUR - 392kc - Eureka, MT - 100W
EX - 374kc - Kelowna, BC, CAN
FCH - 344kc - Fresno, CA - 400W
FN - 400kc - Ft. Collins, CO
FO - 250kc - Flin Flon, MB, CAN
GLS - 206kc - Galveston, TX - 2KW
GUY - 275kc - Guymon, OK - 25W
GW - 371kc - Kuujjuarapik, QC, CAN
HQG - 365kc - Hugoton, KS - 25W
IOM - 363kc - McCall, ID - 25W
ITU - 371kc - Great Falls, MT - 100W
IY - 417kc - Charles City, IA - 25W
JW - 388kc - Pigeon Lake, AB, CAN
LBH - 332kc - Portland, OR - 150W
LFA - 347kc - Klamath Falls, OR
LV - 374kc - Livermore, CA - 25W
LW - 257kc - Kelowna, BC, CAN
LYI - 414kc - Libby, MT - 25W
MA - 326kc - Midland, TX - 400W
MEF - 373kc - Medford, OR
MF - 373kc - Rogue Valley, OR
MKR - 339kc - Glascow, MT - 50W
MLK - 272kc - Malta, MT - 25W
MO - 367kc - Modesto, CA - 25W 
MOG - 404kc - Montegue, CA - 150W
MR - 385kc - Monterey, CA
NO - 351kc - Reno, NV - 25W
NY - 350kc - Enderby, BC, CAN
ON - 356kc - Okanagan, Penticton, BC, CAN*
OT - 378kc - Bend, OR
PBT - 338kc - Red Bluff, CA - 400W
PI - 383kc - Tyhee, ID
PN - 360kc - Port Menier, Anticosti Is., QC, CAN*
PTT - 356kc - Pratt, KS - 25W*
QD - 284kc - The Pas, MB, CAN
QQ - 400kc - Comox, BC, CAN
QT - 332kc - Thunder Bay, ON, CAN
RD - 411kc - Redmond, OR - 400W
RPB - 414kc - Belleville, KS
RPX - 362kc - Roundup, MT - 25W
RYN - 338kc - Tucson, AZ - 400W
SAA - 266kc - Saratoga, WY - 25W
SB - 397kc - San Bernardino, CA - 25W
SBX - 347kc - Shelby, MT - 25W
SIR - 368kc - Sinclair, WY
SX - 367kc - Cranbrook, BC, CAN
SYF - 386kc - St. Francis, KS - 25W
TAD - 329kc - Trinidad, CO
TV - 299kc - Turner Valley, AB, CAN
TVY - 371kc - Tooele, UT - 25W
ULS - 395kc - Ulysses, KS - 25W
VQ - 400kc - Alamosa, CO
VR - 266kc - Vancouver, BC, CAN
WG - 248kc - Winnepeg, MN, CAN
WL - 385kc - Williams Lake, BC, CAN
XD - 266kc - Edmonton, AB, CAN
XH - 332kc - Medicine Hat, AB, CAN
XS - 272kc - Prince George, BC, CAN
XX - 344kc - Abbotsford, BC, CAN
YAZ - 359kc - Tofino, Vancouver Is., BC, CAN
YBE - 379kc - Uranium City, SK, CAN
YCD - 251kc - Nanaimo, BC, CAN
YHD - 413kc - Dryden, ON, CAN
YJQ - 325kc - Bella Bella, BC, CAN
YK - 269kc - Castlegar, BC, CAN
YKQ - 351kc - Waskaganish, QC, CAN*
YL - 395kc - Lynn Lake, MN, CAN
YLB - 272kc - Lac La Biche, AB, CAN
YLD - 335kc - Chapleau, ON, CAN
YLJ - 405kc - Meadow Lake, SK, CAN
YMW - 366kc - Maniwaki, QC, CAN*
YPH - 396kc - Inukjauk, QC, CAN
YPL - 382kc - Pickle Lake, ON, CAN
YPO - 401kc - Peawanuck, ON, CAN
YPW - 382kc - Powell River, BC, CAN
YQZ - 359kc - Quesnel, BC, CAN
YTL - 328kc - Big Trout Lake, ON, CAN
YWB - 389kc - West Bank, BC, CAN
YWP - 355kc - Webequie, ON, CAN
YY - 340kc - Mont Joli, QC, CAN
YYF - 290kc - Penticton, BC, CAN
YZH - 343kc - Slave Lake, AB, CAN
ZP - 368kc - Sandspit, QC IS., BC, CAN
ZSJ - 258kc - Sandy Lake, ON, CAN
ZSS - 397kc  Yellowhead/Saskatoon, SK, CAN
ZU - 338kc - Whitecourt, BC, CAN
Z7 - 408kc - Claresholm, AB, CAN
3Z - 388kc - Taber, AL, CAN*




* = New NDB heard



Mackay Radio & Telegraph Company


  MW, LF & VLF Radio Receiver  Type 105-A

Serial No. 32081

Commercial Shipboard Receiver from 1932

16kc  to  1500kc


built by: Federal Telegraph Company

Mackay Radio & Telegraph Company was founded by Clarence Mackay, son of John W. Mackay, one of the "Big Four of the Comstock" fame in Virginia City, Nevada. John Mackay initially made his fortune in Comstock silver but he later (1883) moved into telegraphic communications. Mackay, along with J. Gordon Bennett Jr., formed several telegraph communications companies to compete with Jay Gould's Western Union. Postal Telegraph Company (1886) was the best known, along with Commercial Cable Company (1884). Eventually, these companies, along with other Mackay-Bennett telegraph companies, had transoceanic cables across both major oceans. When John Mackay died in 1902, Clarence inherited the businesses. Clarence Mackay saw to the completion of the transpacific cable in 1904. Radio was added to the business end of things in 1925 to provide "radiogram" service to every area of the world. Mackay Radio was mainly interested in maritime communications which went along with the maritime radio-telegraph business. By 1928, ITT had merged with most of Mackay's business interests but the Mackay name continued on for  several decades. Mackay Communications is still in business, located in North Carolina.

Federal Telegraph Company started out in Palo Alto, California mainly dealing in arc transmitters. At one time, Lee DeForest worked for the company but Frederick Kolster was the chief engineer for most of FTC's history. FTC bought Brandes and created a new division of FTC called Kolster Radio Company specifically for selling consumer radios in the mid-twenties. FTC became involved with Mackay Radio in 1926 when Mackay bought a radio station that had belonged to FTC. When Mackay sold his interests to ITT, Federal Telegraph Company continued to do most of the Mackay Radio work under contract to ITT. Federal Telegraph moved to New Jersey in 1931 after it was purchased by ITT. For awhile ITT tried the consumer radio market with Kolster International but it was a short-lived venture. The name of Federal Telegraph Co. was changed to Federal Telephone and Radio Company in the 1940s.


photo left:  Federal Telegraph Company building in California about 1927

photo above: The chassis of the Mackay 105-A. The rectangular box on the right side of the chassis contains the power input filters. The right side cylinder contains the RF choke while the remaining cylinders contain the AF interstage coupling transformers.



photo right: The underside of the Mackay 105-A. The lower coils are the Antenna Tuning coils and the upper coils are the Detector Tuning coils.

The Type 105-A is a pre-WWII commercial shipboard receiver that dates from after the Federal Telegraph move to New Jersey since the ID tag lists Newark, N.J. as FTC's location. Later Mackay radios incorporate the year of manufacture into the first two digits of the serial number. It looks like this is also the case with the Type 105-A and, with the serial number 32081, this receiver was built in 1932. The circuit uses four tubes that are five-pin cathode-type tubes. It is possible to use type 27 or type 56 tubes and with an increase in the filament voltage, type 76 tubes could also be used. The frequency coverage is 1500kc down to 16kc in seven tuning ranges. Power is supplied by batteries. Like earlier designs for shipboard receivers, the Mackay 105-A utilizes an LC Antenna tuner ahead of the regenerative detector to increase gain and selectivity. An Antenna Series Condenser switch selects various value capacitors to match the ship antenna to the receiver input and a stepped Tone control provides some relief from static. The panel meter is a dual meter that normally reads filament voltage but B+ voltage can also be monitored by activating a panel switch. The left large tuning knob tunes the Antenna Condenser, the middle large knob controls the Regeneration Condenser and the right large knob tunes the Detector Condenser. The Mackay 105-A is built for shipboard use being physically stout and very heavy. Originally the receiver was probably in a metal cabinet but later it could also have been panel mounted in one of the Mackay Marine Radio Units that  would have housed the majority of the radio gear for the ship.

photo above: This is the radio room onboard the S.S. Manhattan, ca. 1938, entirely equipped with Mackay Radio and Telegraph Company gear. The Type 105-A receivers are flanking the central transmitter in the photo. The receiver to the right of the "right-side" Type-105-A is a shortwave receiver, the Type 104-B. This photo is from the frontispiece of Sterling's THE RADIO MANUAL, 3rd Edition, 1938.
This Type 105-A was an eBay find that was purchased in October 2009. The receiver has vintage modifications that were probably installed during its life as a "shipboard receiver." The original concept appears to have been designed for exclusive DC operation. The Filament control has been bypassed since cathode tubes were now being used and since cathode type tubes are used, AC could be supplied to the tube heaters. However, AC voltage won't read on the panel meter since it doesn't have an internal rectifier - also the internal series resistor is burnt out for the B+ section of the meter. Additionally, there was a DC voltage input filter on the filament line that has been bypassed. I have examined this Type 105-A carefully and it appears that the five pin tube sockets are not original but the rework looks vintage. It could be that the receiver was rebuilt at the factory sometime in its past resulting in professional looking rework and the patina of age appearing on the solder joints. The good news is that this Type 105-A is a working receiver. It operates very much like the IP-501-A in that the position of the regeneration control is dependent on how you set-up the Antenna Tuning. Though there is no coupling control, the interaction between the Antenna Tuning and Regeneration does about the same thing as setting the "Critical Coupling" on the earlier IP-501-A. The Antenna Series Condenser switch compensates for use of a single antenna length and adds to the range of the Antenna Tuning. The Tone Control knocks down the static noise on the LF and VLF ranges. At first, I used an old Signal Corps power supply that provides 6.3vac and regulated 135vdc to power up the Type 105-A. Using the 135' Tuned Dipole antenna with the feed line shorted at the receiver antenna terminal, I was able to easily receive all of the usual longwave signals using WE 509W 'phones for the audio output. Some of the NDBs tuned in were MM 388kc from Fort McMurray, Alberta, ZP 368kc Sandspit, BC for best DX but also consider SYF 386kc, a 25W marker beacon in St. Francis, KS. The VLF reception included the Navy NSRTTY stations in Jim Creek, WA (24.8kc) and Cutler Maine (24.0kc.)

Update on Mackay Type 105-A Performance: The high noise level of the Type 105-A seemed to be limiting the reception of very weak signals. I finally decided to run the heaters on DC voltage which was a subtle change and hardly noticeable but very weak signal detection was improved. I was able to receive WG 248kc in Winnepeg, MB and RL 218kc in Red Lake, ON. Note that both of these NDBs are in the 200kc - 250kc part of the spectrum - a particularly noisy area. DC voltage on heaters does help on weak signal detection. 

Additional Note on Set-up and Performance: I decided to try an entirely different DC power supply set up using a 6vdc 4A Lambda power supply for the tube heaters and a vintage B eliminator, the RCA Rectron, to test if the noise would be further reduced. The change was amazing! Apparently the old Signal Corps power supply wasn't filtered as well as the Rectron because now the MCW signals from NDBs have no distortion and the tone sounds like a good sine wave. Luckily, there happened to be a true CW station operating on 425kc during my test. This was probably an "events" type of operation of one of the old Point Reyes stations since the signal was very strong and was only "on the air" for about one hour. This CW also was very pure in tone. The operation and performance of the Mackay Type 105-A only seems to improve that closer one gets to operating it on pure DC (as original.) November 21, 2009



National Company, Inc.


Intermediate Frequency Receiver (LF and MW)


Serial Number:  3


160kc to 630kc


History - National Co., Inc. built their first contracted "airport" receivers in 1932. The first superheterodyne was designated as "RHM" and was part of a contract with the Department of Commerce, Aeronautics Branch, Airways Division & Lighthouse Service. The DOC wanted to upgrade all radio communications and navigation equipment at the many airports that were already servicing Air Mail routes and were beginning to provide air travel and other types of air services throughout the USA. General Electric was contracted to build the ground transmitters and Aircraft Radio Corp built the airborne equipment. National was contracted to build the ground receivers. The RHM was a nine tube, superhet with plug-in coils that covered 2.3mc to 14.8mc, a micrometer Type-N tuning dial and all aluminum construction. The circuit used single preselection and two IF amplifiers operating at 500kc. Three plug-in coils were necessary for each of the five bands thus totaling 15 coils. Each installation also included a Model 58C Monitor receiver, a GRDPU dual power supply, coil rack and rack speaker all mounted in an open frame relay rack.

About 100 RHM receivers were built to fulfill the initial contract. National wanted to benefit from the prestige of the government contract by selling these types of receivers to the ham and shortwave listener market. After installing a few upgrades the new receiver was released as the "AGS" in 1933. Frequency coverage of the AGS was from 1.5mc to 20.0mc. The IF remained at 500kc. In late-1933, the "Single Signal" AGS-X was introduced. This version had the Lamb Crystal Filter installed and also moved the BFO frequency adjustment to the front panel.    >>>

>>>  The "Single Signal" AGS-X had other accessories such as band spread coil sets for 160, 80, 40 and 20 meters. By late-1934, 10 meter coil sets were also available. The high price of the AGS-X limited its market and National never produced any of the RHM-AGS line in any significantly large quantities.

As airport communications and airways navigation requirements evolved so did the National receivers that were being supplied for these services. The RHM was upgraded to the RHQ, a receiver that ganged the three plug-in coils into one assembly that allowed plugging in all three coils at once. In other services the RHQ was designated as the AGU. The RHQ-AGU frequency coverage was greatly reduced to specifically what the airports needed, 2.5mc to 6.5mc (only two coil sets were supplied.)

Not all airport operations were on HF and much of the Airways Navigation radio needs were on lower frequencies. National also provided an Intermediate Frequency receiver that covered 160kc up to 630kc and was designated as the RIO. The RIO wasn't a superhet, however. This receiver was three stages of TRF amplification followed by a detector and single stage audio amplifier. The circuit also provided a "tracking BFO" that utilized a section of the five-gang tuning condenser to allow the BFO to always track at the tuned frequency. An AVC tube controlled the TRF amplifiers grid bias dependent on signal strength from the detector tube. Only two tuning ranges are provided with the higher frequency range A covering 275kc up to 630kc and the lower frequency range B covering 160kc up to 330kc. The tuning ranges were selected by a panel switch. The RIO was powered by the same type GRDPU rack power supply that the RHM used or it could also be powered by the 5886 "dog house" power pack (as could all of the other receivers in the RHM/AGS family.). Like the RHQ/AGU receivers, the RIO used a Type BX tuning dial (an illuminated SW-3-style dial.) In some National advertising the RIO was also identified as the AGL receiver.

Serial Number 3 - Details - This RIO receiver is virtually "all original." Only one resistor, a cathode resistor on the second TRF amplifier, had been replaced and one paper capacitor was changed. Both changes were performed decades ago based on the resistor style and the orange paper capacitor used for the repairs. As standard for the RHM/AGS receivers, the original capacitors were built by Sprague in the black "postage stamp" style along with a few metal tub capacitors. Resistors are the standard National-made types with the white ceramic body and hand-written values (in blue ink ).

Tubes used are as follows:  1RF = 78, 2RF = 78, 3RF = 78, Det = 37, Audio Output = 89, AVC = 36, BFO = 36. The power pack will also account for a type 80 rectifier tube.

Unlike later USN longwave TRF receivers with a tracking BFO, rather than have the BFO set slightly higher than the tuned frequency (usually 1kc,) the RIO alignment instructions have the user set the BFO frequency to "zero beat" with the tuned frequency. This allowed the user to tune a ICW (Interrupted CW used a rotating chopper wheel to "break" the continuous wave at an audio frequency rate resulting in a modulated CW signal) or "true" MCW signal. The user would then zero the carrier frequency and the modulated CW would be heard somewhat normally. With this method of tuning it was much easier to find weak signals since the carrier was usually easily heard. The RIO uses an output transformer that is a fairly high impedance indicating that hi-z 'phones were probably the intended audio reproducers. If a loudspeaker was needed then either a hi-z armature-pin loudspeaker or a voice coil-type speaker with a matching transformer could be used.

Power-up - When testing the tubes it was noted that every tube was a "U.S.N." tube. The tubes had not been out of their sockets in many decades. This could imply that this RIO was used by the Navy. Not surprisingly, all of the tubes tested good. I also tested a few important components for shorts or continuity and didn't find any problems. I used a National 5886 Dog House power pack (6.3vac and +180vdc) as a voltage source. I connected a set of Navy Baldwin Type C 'phones for audio reproducers. With power applied, the dial lamp came on and within about 20 seconds audio was being received. I had the RIO on Band B at the top end so KPLY on 630kc in Reno was coming in strong. All switches were noisy or intermittent (as expected) but AM BC signals were being received. I later tried Band A with the BFO on and tuned in the DGPS node on 314kc and it was coming in fairly strong. Any switching to either Band A or B resulted in extreme "static" in the 'phones. If the BFO is on then the AVC must be turned off so any noisy contacts are routed thru the audio system unattenuated - ouch!

Even through the RIO seemed to function, it really needed a thorough servicing, especially contact cleaning and alignment. To clean the tuning condenser and the bandswitch required removal of the tuning condenser shield and the bandswitch shield. DeOxit was brushed onto the contact surfaces and the component operated to work out the corrosion. I also lubricated the bearings on the tuning condenser to reduce the drag on the BX dial as much as possible. The improvement was dramatic. The bandswitch could be now operated without severe noise being generated and the BFO operation was stable. Tuning was light and didn't slip. The SPKR-TEL switch needed contact adjustment since in the SPKR position there was no connection to the output terminals. The switch was a cam-operated finger-contact type of switch that needed cleaning and a slight adjustment for a positive contact.

photo left: The tuning condenser shield removed to show the five-gang air variable tuning capacitor. The rear-most section is the tracking BFO capacitor.



photo right: The bandswitch shield removed to show the five section, two position bandswitch.

Alignment - Alignment is very easy since the RIO is a TRF receiver. Peaking the RF coil trimmers and aligning the BFO are all that's required. The procedure starts with Band A and finishes with Band B. There is a pencil notation (see photo right) on the back of the front panel indicating "Realigned 9/12/35 FHS Tubes OK" and that probably was the last time this RIO was aligned. Alignment provided a major improvement on both tuning ranges. The trimmers on most of the RF coils needed considerable adjustment to "peak" the test signal. After alignment the MVC gain could be reduced to only 20% advanced for headset listening. BFO has adjustments on both bands since it has to track the tuned signal. Band A BFO was slightly off but Band B BFO was so far off that several turns were required on the trimmer to get the BFO in tune with the signal. After alignment was complete the RIO was connected to a the 135' CF Inv-vee with 96' of ladder line that was shorted together. This antenna, although not designed as a LF antenna, does a good job as a sort of "T" antenna. During test-listening I heard KPH on 400kc running true CW at 25WPM to honor Memorial Day. This was at 1100 PDT 5/26/18. Strong signal with clear note. Easy copy.  

The fact that the RIO does function on almost all original parts after many decades of idle storage and static display is an indication that National used the very best components available in 1933 for the construction of the receiver. Of course, the circuit is fairly simple and that also might account for the reliability.

Performance - The first thing to remember when listening on the RIO is that there isn't any type of noise limiter or bandpass filters or output limiters,...nothing to suppress noise. Any pulse-amplitude noise is going to disrupt your hearing when using 'phones for audio reproduction. The old radio ops always kept the 'phone cups slightly in front of their ears to avoid painful discomfort when listening in a noisy environment.

The RIO is very sensitive with the manual specs indications as low as 1uv. But at MW and LF that level of sensitivity is usually lost in the ambient noise. Using a low-noise antenna is a real benefit. The remotely tuned loop antenna provides the low noise necessary to take advantage of the receiver's sensitivity. Of course, late-spring isn't the best time of the year for testing a longwave receiver but some regional NDBs can be heard. Listening at 10PM on 5/27/2018 using the wire antenna I heard, MOG 404kc, XX 344kc, ZP 367kc, NY 350kc and DC 326kc. Except for MOG, the remaining NDBs heard were all Canadian beacons that tend to run more power. Conditions were terrible with high static levels that sometimes bordered on painful. The next test will be with the loop but the best test results will be those conducted during November through January.  This performance information will be updated when better listening conditions allow for a more thorough test.


RCA Manufacturing Co., Inc.

Navy Department
Bureau of Engineering


RF Tuner - CRV-46034-A
IF/AF Amplifier - CRV-50022-A
Power Unit - CRV-20016-A


Superheterodyne Receiver - 1935

built by RCA Manufacturing Co., Inc.


10kc  to  1000kc


This is a teaser, a preview,...a way to let longwave enthusiasts know what's coming up pretty soon. I've been working on the 1935 RAA-3 since June 2017. I'm hoping to have the receiver operational by the end of the summer of 2019. This 465 pound, over three feet wide, behemoth of a receiver has three sections,...the RF Tuner, the IF/AF Amplifier and the "not shown in the photo" Power Supply. The RAA was the first long wave superheterodyne built for the US Navy in 1931. This receiver is the RAA-3 from 1935. It has 14 tubes, 4 individual 2-stage IF amplifiers that are selected by the band switching and a lot more. This ultra-rare receiver was in absolutely horrible condition after having been stored outside for decades, wrapped-up in a tarp. However, it's restoration is now finally coming together. Go to "Navy Department - RCA RAA-3 Superheterodyne Long Wave Receiver" article that details the restoration process so far - use navigation index at the bottom of this page.

Radiomarine Corporation of America

  U.S. NAVY - RAZ-1

 MW, LF & VLF Radio Receiver - 1941   

Serial Number: 65

CRM-46092, CRM-50092, CRM-20096

aka: AR-8503, AR-8503-P, RM-6

15kc  to  600kc

The Radiomarine Corporation of America was a division of RCA that specialized in the operation of RCA's Communications Stations and sold RCA-built equipment for both major communications stations and for shipboard installations. The AR-8503 was introduced around 1938 and was designed mainly for shipboard installations. A matching pre-selector was also included, designated as the AR-8503-P. Additionally, an AC power supply was offered, the RM-6. Although in an emergency, the AR-8503 could be operated from a battery pack the preferred method of operation used the RM-6 to supply the required 6 volts for tube heaters, +22 vdc for the detector B+ and +90 vdc for the amplifier plates. Sometime around 1941, the US Navy wanted to install the AR-8503 on some of their smaller ships and a contract was issued for a small number of receivers. "RAZ-1" designated a complete set of equipment that included the CRM-46092 Receiver (AR-8503) with the matching CRM-50092 Pre-selector (AR-8503-P) and the CRM-20096 Power Supply (RM-6.) The contract date was just five days before the attack on Pearl Harbor, Dec 2, 1941.

The CRM-46092 receiver uses four metal octal tubes in its regenerative circuit. The RF amplifier, detector and first audio are all 6K7 metal octal tubes while the audio output tube is a 6F6. The CRM-50092 preselector uses a single 6SG7 metal octal tube as a tuned RF amplifier. The CRM-20096 uses a 5Z4 metal octal tube for the rectifier. The CRM-50092 pre-selector receives power from the CRM-20096 power supply via a three foot long, three conductor cable that is connected to the power supply ground terminal along with the 6vac terminal and the +90vdc terminal. The CRM-46092 receiver has four tuning ranges covering 15 KC up to 600 KC. Three bandswitches - two on the receiver and one on the preselector - have to be utilized for changing tuning ranges. The National Type-N dials are scaled 0 to 100 and have a 180 degree layout. A tuning chart is provided in the manual to correlate the dial reading to tuned frequency. Coupling, Regeneration and Volume controls are on the front panel and the preselector also has an RF Gain control. Audio output is provided for a single audio stage or for full audio output via two telephone jacks on the front panel. Output is designed for the Western Electric 509W earphones and, although any Hi-Z 'phones will work, the 509W phones seem to give the best immunity to noise. The receiver case is shock mounted and is made of copper plated steel painted a grayish-brown color. The preselector case is made of aluminum and painted to match the receiver although it is not shock mounted. The power supply is a standard steel box painted gray. The front panels of the receiver and the preselector are machine textured aluminum that has been matte chromium plated.

Left photo: The CRM-46092 chassis showing the large bee's wax dipped coils and the sparse layout of components. The tuning condenser is inside the shielded box in the center of the chassis.




Right photo: The CRM-50092  preselector chassis showing the tuning condenser and the 6SG7 RF amplifier tube. The RF coils are under the chassis.

I first saw this RAZ-1 in 1997 at the home of W3ON, John Ridgway. It was setting next to the SX-28 he was going to sell me (if I could lift it off of the table.) I asked John if he wanted to sell the RAZ-1, to which he replied, "You wouldn't take a longwave receiver away from an old Navy radioman, would you?" John was living in Galena, Nevada at the time but since he was 85 and now alone, he was moving back to Maryland. John lived to the age of 93, becoming an SK in January 2006. To my surprise, in the summer of 2006, I got a 'phone call from an estate agent who said that they had found a letter among John's papers that stated that he wanted his radios and parts to be sent to the "Radio Museum in Virginia City, Nevada." The agent was calling me to see if I really wanted any of "this junk." I told them I did. The estate paid to ship the parts and equipment back out west. The shipping of the 22 boxes was spaced out over about a six week period. In the 21st box was the RAZ-1. Shipping had caused one small problem, one of the largest coils had broken from its mount. The large buss wiring had kept it in place and all that was required was to glue the mount back together and screw the coil form back in place. I acquired the correct shock mounts from N7ID. I did have to replace the filter capacitors in the power supply for quiet reception.

The RAZ-1 is very sensitive and almost any station on LW can be tuned in however the lack of a calibrated dial makes this somewhat difficult if looking for a specific frequency just using the RAZ-1 dial alone for reference. Though I could use a heterodyne frequency meter if it is important to determine the exact frequency being received, I find it is easier to know approximately where I am tuning by listening to known adjacent signals. In other words, if the NDB MOG is zero beat (or being heard in the background) and I'm trying to copy another weaker signal partially obscured by MOG, I know that weak NDB is on 404kc or very close to it, since that is MOG's frequency. I can usually determine an unknown NDB's frequency within 1 or 2 kc by this method. The lack of any kind of limiter is sometimes a problem if local noise is present, however switching to the loop antenna has greatly reduced local noise. To reduce noise to a minimum, the Coupling is set very close to zero (0 to 25% maximum,) the Volume about 25% to 60% advanced, Regeneration right on the oscillation point (autodyne detection) and then signals are peaked with the the Preselector and then slightly manipulated with the Trimmer control. The Preselector gain is usually set to about 85%. These settings usually result in the best response of signal to noise along with the greatest selectivity. Although very strong signals are encountered from local or powerful stations, very weak MCW signals are the norm when searching for DX NDB stations. Usually, with several NDBs on the same frequency it is possible to slightly de-tune the loop antenna to one side or the other of the frequency and enhance one or more of the NDB signals for successful copy. I have probably logged more NDBs with the RAZ-1 than any other LW receiver. However, that might be because it was one of the first LW receivers that I used when I started logging NDB stations. But, it can always be relied upon to pickup whatever is out there as long as reasonable conditions are present.
A Second RAZ-1 - I was lucky enough to be given a second RAZ-1 in trade for some radio work in 2013. This RAZ-1 didn't have the CRM-20096 power supply but it did have the CRM-50092 preselector. There were a few condition problems that required some unusual cleaning methods to correct. I had to use NaOH (found in Easy-Off Oven Cleaner) to remove the corrosion on the National Type-N dial on the receiver. After cleaning the dial the black nomenclature fill was applied using Artist's Acrylic (Mars Black.) The receiver panel required a fairly hard scrub using a brass brush and Glass Plus. The panel is chromium-plated aluminum so it can take this kind of treatment and come out looking great. At sometime in the past, someone had tried to install a Squelch control - difficult to accomplish with a regenerative receiver that was designed for a headset output. Needless to say, the Squelch modification didn't work and only succeeded in the RAZ then having a hole in the front panel.
I removed the Squelch modification and installed a red jewel pilot lamp housing with lamp into the panel hole. Now the RAZ-1 has a power-on indicator that looks original and provides useful information - something the Squelch didn't. There were a few wiring problems in the preselector due to an unnecessary recap job. The original tub caps were checked and found to be in good condition so the modification was removed and everything put back to original. The cases for both units were cleaned with a brass brush and Glass Plus. This removes all of the dirt out of the convolutions of the wrinkle finish and winds up with the cabinets looking very good. This RAZ-1 works pretty well now - not as well as SN: 65 which is almost all original - but pretty good.

photo left: RAZ-1 sn: 226 with Preselector sn: 182 - the red pilot lamp is next to the power input terminals


Radiomarine Corporation of America


Model AR-8510

MW, LF & VLF Shipboard Receiver - 1944

15kc  to  600kc

The AR-8510 was the replacement receiver for the AR-8503 (aka RAZ-1 for the USN - profiled in a section above) and is a five tube regenerative receiver that tunes from 15kc up to 650kc in four tuning ranges. Two TRF amplifiers are used with a Regenerative Detector and two stages of audio amplification. The RF amplifiers use a combination of tuned grid input and tuned plate output using a three-section ganged tuning capacitor. The antenna switch allows the user to select which receiver will be connected to the antenna - either the AR-8510 or an emergency receiver. The audio output can drive the panel mounted loud speaker or headsets either simultaneously or, using the Loudspeaker switch, the panel speaker can be turned off. The receiver requires a separate power source of which many types were available. Various types of battery combinations could be utilized with either the RM-2 or the RM-4 Battery Control panels. These functioned on ships that provided 115vdc or 230vdc power. If 115vac was to be used then the RM-23 Rectifier (power supply) was used. There was also an RM-37A unit that provided 90vdc B+ output with a 115vdc input from the ship's power. This was to be used if it was necessary to conserve the B batteries that normally provided the +90vdc. The AR-8510 requires 6.3 volts at 1.8A (AC or DC) and 90vdc at 15mA. The vacuum tubes used are four 6SK7 tubes and one 6V6G or GT.

photo right
: Top of the chassis showing the antenna connections (far left front of chassis) and the power input connections (far right back of chassis.) The tuning condenser is under the central cover.

photo above: Under the chassis showing the bee's wax impregnated coils.

The AR-8510 could be provided with a cabinet and shock mounts if it was to be used as a "stand alone" receiver. However, if it was going to be installed into a shipboard communications console (as most were) then the cabinet and shock mounts were not provided. Many AR-8510 receivers were part of the shipboard 3U transmitter console that included a 200W transmitter, an emergency crystal receiver, battery charger switching, clocks and more. The 4U console used the RMCA AR-8506 MW-SW receiver with a larger transmitter. The 5U console had both receivers installed along with transmitters and auxiliary equipment. Mackay Radio and Telegraph Company also supplied Marine Radio Consoles MRU-19 or 20 that had their equipment installed.

The AR-8510 was approved by the FCC for shipboard use in 1942 (concerning minimum radiation from the antenna.) The schematic drawings are dated 1943. It's likely that it was at least 1944 before any AR-8510s were in use and this particular AR-8510 is dated NOV. 1944 (with a serial number of 2774) making it an early example. It seems that most of the installations during WWII were onboard Liberty ships. Post-WWII installations were generally on commercial ships. The AR-8510 found a lot of use and longevity with some receivers still in use onboard some old oil tankers as late as the 1980s.

Unfortunately, most AR-8510 receivers led a pretty hard life and the sea environment didn't help preservation. Most examples have been worked on or have missing parts (or non-original parts.) The AR-8510 shown in the header photo is cosmetically restored with nearly all original parts. The exception is one capacitor under the chassis, the speaker grille and the RCA pointer knobs. The paint job on the front panel is VHT Gray wrinkle finish which is slightly darker than the original RMCA gray.

Later manuals and some Internet sites will show a slightly different AR-8510 that has silk-screened nomenclature on the panel including the information on the data plate silk-screened onto the panel in the upper right part of the panel. The B&W photo (shown right) in the 1950 manual shows this later version with a date on the panel of 1947. It's probable that the WWII version (early version) used the easy-to-replace nomenclature tags as an ease-of-maintenance function. Later post-war receivers were probably not going to be subjected to the rigors that the wartime versions experienced so the silk-screened panels could be used and provided an excellent appearance.

I was given the AR-8510 shown in the photos as payment for some radio repair work. It probably was taken off of one of the Liberty ships that were part of the "moth-balled" fleet that was moored outside of Benicia, California since the receiver originally was obtained from the SF Bay Area. The "as received" condition was fairly good considering how the ships were taken care of - they weren't. Of course, the front panel has been repainted in the past - probably with a brush. The perf-metal grille had more than its share of paint applied (and it wasn't original either.) The receiver came without any type of power supply (the RAZ-1 power unit RM-6 can be used as a power source.)

This AR-8510 required a little bit of work to get it operational. Bands 1 and 2 functioned okay but needed alignment. Band 3 and 4 were non-functional due to broken leads from the coils that are in the plate circuit. The open coils resulted in an absence of plate voltage to the first RF amplifier when bands 3 or 4 were selected. I had to remove the coils and rebuild them then finishing them off with a re-waxing job. After reinstalling, bands 3 and 4 had to be aligned.

Performance using a "T" antenna of 98 vertical feet running to a 135 foot horizontal section was very good. Since the AR-8510 was the replacement for the AR-8503, it's fair to compare the two receivers. First, with a direct readout dial there's no need for the charts and graphs necessary for finding where you're tuned on the AR-8503. The preselector is built-in with the AR-8510. Also, only a single band switch is necessary on the AR-8510 while two band switches are used on the AR-8503 plus a band switch on the preselector. Sensitivity on the AR-8510 is about the same as the AR-8503 with preselector. Regeneration action is very similar in that it's a very sharp adjustment between maximum sensitivity (either non-oscillating or oscillating) and any adjustment below either point greatly reduces sensitivity (this is typical of regenerative detectors though.) The AR-8510 seems to hold its adjustments better across the band especially the Trimmers that only require a slight adjustment from one band end to the other. This is expected since it's part of the alignment process. I find that the loudspeaker is actually pretty good for some reception. If you want to use Hi-Z phones, it's better if you leave the loudspeaker on. Without the speaker load the 'phones seem to respond to more noise than signal.


U.S. Navy


contractors: Andrea Radio Co. or Magnavox

RAK - 15kc to 600kc, RAL - 300kc to 23mc

Andrea Radio Co. CND-46155,RAK-7  - 1944

Andrea Radio Co. CND-46156,RAL -7  - 1944

The Navy wanted more modern LF, MW and SW receivers in the mid-thirties so RCA provided the Navy with the RAK/RAL series. The RAK/RAL were to replace the aging RAG and RAH receivers built in 1933. The RAG/RAH were TRF receivers with non-regenerative detectors and tracking BFOs built by Sylvania. There was an early version of the RAL that was supplied to users other than the USN that was designated as the TBR.

Any receiver built for shipboard use had to be "bullet and bomb" proof, in other words, the ship had to take a couple of torpedoes, be sinking fast and the radio gear would still be working. Additionally, steel and iron was kept to a minimum in shipboard radio construction to reduce corrosion problems that were common on marine equipment. The RAK/RAL series were built like the battleships they served on. The construction is something to marvel at - so over-built, so heavy-duty with no expense spared - it's no wonder that most RAK or RAL receivers still function with all original parts even though they are pushing seventy years old. The design concept was to provide maximum reliability in severe service by simplicity of design - and it paid off since the receivers were in use up until the end of WWII with their last service on board submarines.

RCA was the primary designer and builder of the first contracts of RAK and RAL receivers. During WWII, Andrea Radio Corp. became another contractor building RAK and RAL receivers. The RAK, (aka CND-46155 by its Andrea/Navy designation, substitute "R" for the "N" for the RCA /Navy designation) covers 15kc up to 600kc in six tuning ranges. There was a RAK-8 and RAL-8 produced with Magnavox as the contractor.

The RAK and the RAL used glass tubes that were large six-pin type, 6D6 tubes for the two RF amplifiers, a 6D6 for the regenerative detector, a 6D6 for the first audio amplifier, a 41 for the audio avc amplifier and another 41 for the audio output. The power supply, CNV-20131, was a separate unit that used a 5Z3 rectifier, an 874 regulator tube and an optional 876 ballast tube. The 876 can be left out of the power supply if the AC power is stable and noise free. An internally mounted switch routes the 120vac to a different tap on the power transformer if the ballast is not required. If the ballast tube is installed it will be on regardless if it is used or not although less current is flowing through it when it is switched out of the circuit. When switched in, the 120vac actually is dropped through the ballast and a different tap on the power transformer is used (~70vac) thus providing the regulation of the AC to the transformer if the line voltage is not stable. Since the ship had to generate its own power and most of the equipment onboard (including motors to rotate gun turrets) ran on this power, the varying switching loads are what caused the line voltage fluctuations that required using the ballast regulators. In shore set-ups, on standard AC line power, ballast regulators were not required.

The RAK is designed for CW or MCW only. The receiver has a low pass filter that is permanently connected in the audio circuit to roll off the upper audio frequency at about 1200 hz. An elaborate audio avc circuit allows the user to limit the audio or noise peaks at an adjustable level. This was to allow the receiver to be used in heavy static conditions. Also a selectable audio bandpass filter was provided to enhance CW reception in noisy conditions. Voice can be received but it is severely limited on the higher audio frequencies making copy difficult. The manual states that another receiver should be used if voice reception is required - like the RAL. The tuning of the RAK is heavy duty, gear driven and the tuning dial readout is shown on two circular dial scales of 0 to 10 and 0 to 100. The actual tuned frequency has to be correlated with a graph that is in the manual. The receiver does provide a logging chart on the front panel for a "most used frequencies" reference. A frequency trimmer, an antenna trimmer, sensitivity and regeneration controls on on the lower panel of the receiver. The meters monitor audio output level in db and tube heater voltage. The RAL receiver is almost identical construction but has nine bands covering 300kc to 23mc. Additionally, the low pass filter can be switched out of the circuit for voice reception and a vernier frequency control is provided. Most of the concern about a stable AC line voltage was directed at the RAL receiver which itself can become unstable at high frequencies if the line input varies. Normally, the two receivers operated together through a control box (CND-23073) that allowed the radio op to monitor two frequencies simultaneously. The control box also could be used to switch the AC to the receivers on or off.

photo left: The RAK and RAL in use aboard a US Navy ship. Also, National RBL and RAO receivers far left,  the LM-type frequency meter by the telephone handset and a Scott SLR-type receiver below the order binders.

Nowadays, a RAK and RAL set up will require an ample and heavy-duty table for the complete set-up. In my installation I had the power supplies for the RAK/RAL receivers bolted to the underside of the table. I provided for a space of about 3.5" above the supplies to allow good ventilation for the ballast tubes. I ran the power supplies with their ballasts even though wasn't necessary. The actual difference in power consumption is significant - the ballast dissipates about 140 watts. I had run the receivers both with and without ballasts and I noticed that the received noise seemed to be slightly less with the ballast in use.

In actual operation, the RAK is a very sensitive receiver that spreads the LF tuning range over several bands. This bandspread action is nice for tuning in weak stations or trying to separate several stations that are on the same frequency - as many NDBs are. The major problem is that calibration is relying on the readout versus a graph and that graph is in the manual. The first thing to do is make a copy of the frequency graph to keep with the receiver. Next is to calibrate the RAK so the readout is fairly close to the graph. Then it is easy to keep track of where you are in the LF spectrum. If it is important to know the exact frequency, I use a heterodyne freq-meter set up. The Audio AVC will help with static crashes and to a certain extent, noisy conditions but, like most output limiters, if it is advanced too far it severely clips the audio with high distortion. The adjustable bandpass filters are almost useless. This is due to the high frequency chosen for the first audio frequency cut-off - 450hz. This may have been fine for true CW but that is seldom encountered anymore in the LF bands. All NDBs use MCW with a 400hz tone. The lowest setting of the filter works okay on NDBs but the other bandpass frequencies are even higher in frequency and so are not very useful.

The tuned loop antenna, with its high Q, really helps reduce the noise and increase the signal to noise ratio. The audio output is taken from the front phone jack. It's 600Z ohms and, while the RAK will easily drive a 600 ohm speaker, many more weak signals can be copied using earphones rather than a speaker. I have tuned in all of the normal LF signals with my RAK-7. The best NDB DX were several in North-Eastern Canada and Puerto Rico's powerhouse transatlantic beacon, DDP. At lower frequencies, the RAK seems to get better and better with JJY at 40kc a fairly regular copy. The Navy MSK-RTTY signals from 19.8kc up to 25.2kc are always present.

photo above:
  "Women Marines - USMC PHOTO - 24-8" -  showing a Women Marines Reserve radio op using the RAK and RAL receivers. She's tuning the RAK and is ready to copy on the "mill" (the typewriter.)  RAK and RAL power supplies are on top of the receivers in this set up. Note how she has the 'phones slightly in front of her ears. This helps reduce "ringing ears" from static crashes or unexpected loud "pops" common on the lower frequencies. The RAK and RAL have audio AVC circuits for an output limiter function.


U.S. Army Signal Corps

Farnsworth Television & Radio Corp.



BC-344-D - LF/MW Radio Receiver - 1944

150kc  to  1500kc


SN: 5     Contractor: CFN (Farnsworth) 


Order No. 10651-PHILA-44


The BC-344 belongs to a family of radio receivers that were designed by the U.S. Army Signal Corps at Fort Monmouth, New Jersey in the late-thirties. The early versions of the receiver used more aluminum in the chassis and some early versions were painted with a "leatherette" finish paint (properly called "Crackle Finish.") By the time WWII contractor manufacturing had started, the receiver used an all-steel chassis and the paint used was the standard black wrinkle finish. Farnsworth Television & Radio Corporation built the AC operated versions, those being the BC-342 and the BC-344. RCA Manufacturing Co., Inc. built the DC operated versions, those being the BC-312 and BC-314. The BC-312 and BC-342 are shortwave receivers with six frequency ranges that cover 1.5mc up to 18.0mc. The BC-314 and BC-344 are LF (low frequency) and MW (medium wave) receivers with four frequency ranges the cover 150kc up to 1500kc. The BC-344 has two RF amplifiers and two IF amplifiers (four 6K7 tubes.) A separate Mixer (6L7) and LO (6C5) are used. The BFO uses a 6C5 triode, the detector-AVC-first AF is a 6R7 and the AF Output tube is a 6F6. There are ten tubes used in the BC-344 including the 5W4 rectifier tube used in the RA-20 power pack that mounts internally. No selectivity filter is used in the BC-344. Audio output is generally 4000Z ohms but may be set to 250Z ohms by moving a jumper inside later versions of the receiver. The LS-3 loudspeaker was commonly used with the BC-344 receiver although a headset would allow copy of weaker signals.

photo above: Army communications set-up for local ground transmissions. The telephone box allowed interfacing a telephone contact through the BC-191 transmitter. Note that the vernier dial locks are removed from all three receivers.

The Signal Corps utilized the BC-312/314/342/344 receivers in many applications. Fixed stations generally used two or more receivers paired with at least one BC-191 transmitter. A typical Army station is shown in the photo to the left. Note that three BC-342 receivers are utilized with an AC operated BC-191 transmitter (the RA-34 power supply is barely visible under the transmitter table.) Mobile stations ranged from small vehicle set-ups to the SCR-299 that used a BC-342 and BC-344 set up with a BC-610 transmitter, all powered by an AC generator towed in a trailer. Most DC set-ups operated on 12vdc from vehicle battery-charger systems. There was a 28vdc BC-312 version, the BC-312-NX.

BC-344-N on Long Wave? - I've been interested in how well the BC-344 would perform on MW and LF reception for some time. I have a "rough-condition" receiver that had been painted "metallic" green. I even had it on the work bench once but I lost interest when I saw some "hamster" rework inside. Recently (2016,) I obtained another BC-344 receiver that happened to have the scarce shock mount installed. This receiver seemed to be pretty original and virtually complete. Replacements for the few missing or poor condition parts were easily located in my BC-312/314/342/344 junk box.

Reworking the BC-344-D - Since the BC-312/314/342/344 were essentially "workhorses" for the Army, many are in rough condition today. All will require some work and many require a full restoration in order to function correctly. The receiver is difficult to disassemble and this has saved many BC-344s (and 342s) from being modified too much by hams. Most hams preferred to modify the easy-to-work-on BC-348-Q. Most 344/342 receivers will be very close in alignment because all of the adjustments were "locked" if they were easy to access, like the IF transformers, or hidden by covers or plugs in the case of the RF adjustments. Most receivers will be missing the dial lock since this piece often times interfered with the rotation of the vernier knob. It's not unusual to do mostly a cosmetic restoration and have the receiver work with all original parts with the exception of the dual electrolytic filter capacitor located in the RA-20 power pack.

Front Panel Dismounting - One of the common problems with any of this series of receivers was present on this BC-344. That is, the plastic dial index that always seems to have warped, cracked and discolored to the point where it's no longer even transparent. Luckily, I had an excellent condition replacement. Unfortunately, to install the index requires completely dismounting the front panel.

I say "unfortunately" because this task is unbelievably complicated by the Army's mechanical design that never seemed to even consider the possibility that the receiver might need to be disassembled someday. Besides the abnormal amount of front accessed screws there are three screws that mount from the backside of the panel that must be removed. The two fuse holders must be unsoldered and removed. All of the phone jacks and controls must have their mounting nuts removed. The wires to the dial lamps have to be unsoldered. All of the wires going to the front panel "trunk" connector have to be unsoldered. The power input terminal strip has to be dismounted. All screw connections to Antenna and Ground connections have to be dismounted. Knobs and control nuts must be removed. At this point, you'd think the front panel would easily come off, but not yet! The Fast Tuning gear has a pinned shaft that is flanged. You can't remove the front panel unless the gear and shaft are taken apart and that requires driving out the pin. However, once the gear and flanged shaft are apart, the front panel finally can be dismounted.

photo right: A rear view of the chassis showing the stout construction of these receivers

At this point, installing the replacement dial index is easy (it's mounted with eight screws!) Since the front panel is off, now is the time for a thorough cleaning and touch-up. I use jet black nitrocellulose lacquer that is thinned about 3:1 for touch-ups. After the lacquer has set for a while, I rub down the panel with light weight machine oil. Usually, this will blend the color of the touch-ups with the original black wrinkle paint making the touch-ups invisible.

When remounting the front panel, it will be noted that all of the 6-32 screws are the same length. However, there are three different length 4-40 screws. The four long 4-40s are for the wire mounts. There are two short 4-40s and the rest are all the same length. The two short 4-40s are very important. There are two places where, if long 4-40 screws are used, they will protrude far enough thru the rear panel mounted nut to contact the dial mask with possible scratching of the mask when the band switch is operated. The "short" 4-40 screws must be mounted as follows: One "short" screws is by the band change switch and is the screw nearest the "G" in "CHANGE" in the nomenclature of that switch. The other "short" 4-40 is used near the lower left side of the data plate (the screw head almost is contacting the data plate edge.)

The other observation is the small component board that is mounted to the back of the front panel uses two different length stand-offs. The reason is that the lower screw must past thru a part of the chassis mounting flange and the top screw doesn't. The longer stand-off is the upper one.

Patience is required in any BC-321,314,342,344 rework. The work is tedious and none of the component parts are easy to access without removing another part or assembly first.

  Electrolytic Filter Capacitor - Most military gear used oil-filled paper dielectric capacitors as the filters. The disadvantage of this type of capacitor was its large size but the advantage was long-term reliability. Since space was at a premium in the RA-20 power supply, a dual electrolytic filter capacitor was used. The advantage was a small size for two 8uf 450vdc caps but the disadvantage now is, after 75 years, the dielectric paste has dried up and drastically reduced the value of the capacitor.

There's ample room to mount new electrolytic capacitors inside the old capacitor can. There are many methods to accomplish this "re-stuffing." I cut the cap in two and remove the old cap and black wax using a heat gun to soften the wax. This allows the old capacitor to be easily pulled out of the can. I install new capacitors connecting them to the correct terminals and then epoxy the can back together. I remount the rebuilt cap and connect it into the circuit.

The photo to the left shows the underside of the BC-344 and in particular the RA-20 power pack. Note that the RA-20 is "swung out" on the right side hinge mount. Also note the wiring harness that is connected to the power terminal strip. 

Miscellaneous Rework - Sometimes the OFF-MVC-AVC switch contacts don't allow the operator the ability to turn the receiver on. These are special build, stacked switches that have the MVC and AVC switches enclosed. Luckily, the AC on/off switch is only covered with a fiber disk that can be bent to allow access to the arm and contacts. It's usually only dirt or maybe minor corrosion that is causing the problem. This can be cleaned off using a small piece of Alu-Ox paper or a very small wire brush. It might be necessary to bend the arm slightly to have better contact. If the AC contacts are damaged beyond reconditioning then the entire switch has to be replaced with a used-good original. These are sometimes difficult to find except from parts sets. The same switch is used on all of the versions of the BC-312, 314, 342 and 344. Alignment Notes - IF is 92.5kc. Note in the photo above left that the large LO box (far left) has four plugs that are covering access to the trimmers for each band. Also note the shield cover over the two RF amp boxes and the Mixer box that is preventing easy access to these trimmers. Each IF transformer adjustment has a lock nut on the threaded shaft to prevent tampering (see photo above right showing top of chassis.) Other than the lower frequencies involved, the BC-344 is straight forward in its alignment procedure.
Performance on a Wire Antenna -  The antenna used was my 135' CF Inv'd Vee with 96' of ladder line with the two feed line wires tied together. This is something like a "T" antenna and it performs fairly well on LF. The test listening was on January 29, 2018 from 1915 to 1945 PST. I only tuned the BC-344-D from 405kc down to 300kc. Within the frequency span and time period I tuned in 25 NDBs. Greatest USA DX was IN 353kc in International Falls, MN. Greatest DX was YMW 366kc in Manawaki, Quebec, CANADA. Another Canadian NDB tuned was YXL 346kc in Sioux Lookout, Ontario. Listening QTH was Dayton in Western Nevada.

All signals were heard over a headset, not by loudspeaker. BFO was on and stations generally tuned for zero beat of carrier to then hear the MCW tone correctly. The AVC was off. Noise level wasn't too bad and I'd rate the conditions as "very good."

The BC-344-D is a capable LW receiver that has ample sensitivity in the medium wave portion of the spectrum using a wire antenna. There is no crystal filter or any other method to reduce IF bandwidth so many signals are "heard" over what seems to be a fairly wide IF passband. It's easy to select one particular signal and then concentrate on that tone or sound of the signal to then successfully copy the call. Most of the time this process will be with very, very weak signals that are within the passband with stronger signals. If the received noise seems to be covering up some weaker signals it's possible to slightly "detune" the antenna trim (ALIGN INPUT control) to reduce the noise while not affecting signal copy.

While the BC-344-D is kind of a "basic" superhet with no fancy filters or output limiters, it does a good job with the few controls provided. It's certainly sensitive enough and the reduction of the VERNIER tuning mechanism allows for easy tuning of all stations, including NDBs. Without an output limiter though there isn't any way to reduce "pops and clicks" or heavy static. Wearing the 'phones just ahead of the ears is recommended. I'm sure if the BC-344-D was used with a wire antenna in a modern RFI-noisy, urban-type location the weak signal DX reception would be terrible. But, in the rural RFI-quite area here in Dayton, NV, the BC-344-D does a very good job of pulling in NDB DX using just a wire antenna.

Performance on  a Tuned Loop Antenna - The remotely tuned loop is six feet "point to point" of its diamond-shape and tuned using varactor diodes with a variable bias voltage source. The receiver is connected to a pick-up loop that is mounted within the main loop. Test listening was on February 1, 2018 from 1930 to 2000 PST. I only tuned the BC-344 from 325kc up to about 390kc. 23 NDB stations were tuned in during that time. Conditions were very good. Greatest USA DX was FIS 332kc in Key West, FL. Greatest Canadian DX was GW 371kc in Kuujjuarapik, Quebec, CAN.

All signals were heard over a headset, not by loudspeaker. BFO was on, AVC was off. Loop Antenna was pointing NE/SW for the entire test listening period.

The BC-344-D running with the tuned loop antenna is a surprisingly good performer. Without any bandwidth controls, one would expect noise to be a problem but the loop does keep the noise level somewhat lower than the wire antenna. Additionally, the "loop tuning" provided the ability to slightly detune the peak adjustment which lowered the noise without causing loss of the signal. This was a nice advantage for signals that were "in the noise." Also, the ALIGN INPUT (antenna trimmer) could be used to slightly detune the antenna and reduce the noise peaks allowing some weaker signals to be copied. These two features, loop tuning and antenna trimmer, do a lot to make up for the "wide open" IF bandwidth which does have a tendency to be somewhat noisy.

As mentioned in the "wire antenna test" section, the BC-344-D is a pretty basic receiver with no filters or no bandwidth control. Yet, I was still able to copy NDBs all the way to the east coast and Canadian NDBs out to Quebec. I don't think any vintage LW receiver enthusiasts will be going out to purchase a BC-344-D to use as their main LW receiver, but I was impressed with its performance and would rate the receiver as one of the better medium wave and low frequency receivers. It is fully capable of receiving DX LW signals and, with its incredible "WWII Military" appearance, makes a fine addition to any collection of vintage LW receivers. Additionally, if you get tired of listening to MCW signals on 'phones, you can always tune in almost the entire AM BC band and listen on an LS-3 loudspeaker - very cool.


National Co., Inc.



   RBL-5, CNA-46161-B  - MW, LF & VLF Radio Receiver - 1945

15kc to 600kc

National Company also provided a great LW receiver for the Navy in WWII - the RBL series of regenerative receivers. Following the long Navy tradition of  National providing NC-100A types of receivers - like the RAOs and similar HF receivers, the RBL series uses the same general appearance with a similar dial layout and a familiar band switching feel. Though the bandswitch looks like the RAO catacomb system, it isn't. The mechanism uses several large gears to simultaneously actuate two large ceramic switches to provide band changes. The RBL is the same approximate size as the RAO receivers so it was probably intended that they be paired up for coverage from 15kc to 600kc on the RBLs and 540kc to 30mc on the RAOs. Unlike the earlier LW receivers described above, the RBL has a built in power supply and has direct frequency readout on the illuminated dial. Like the RAO receivers, Wells-Gardner Company was a second contractor and built the RBL-3 and RBL-4 versions under contract using many National parts for assembly (see RBL-3 at the bottom of this write-up.)
The circuit uses a cascade of three 6SK7 RF amplifier stages. The detector is a 6SG7 regenerative autodyne detector followed by a 6H6 audio limiter circuit followed by a 6K6G audio tube. The power supply rectifier is a 5U4 in early RBLs but later was changed to a 5Y3G. Like the RAO, some RBL receivers were built by Wells-Gardner Company. Heavy duty construction, ample shielding, copper-plated cabinet under the black wrinkle paint are standard construction used in the RBL receivers. They were normally bolted to a cushioned mount that attached to the holes in the lower front and rear corners of the cabinet. Nowadays these mounts are usually missing. Included in the circuit is an audio filter for wide or narrow bandwidths (switch on left side of escutcheon below ON-OFF switch) and an adjustable audio limiter (switch and control on right side of escutcheon.) The limiter is very well designed and works wonders in reducing the static crashes while not distorting the audio signal. The direct frequency readout on the dial is the major advantage of using the RBL receivers and the accuracy is impressive considering the receiver's age. The illuminated dial is quite a departure from the usual military LF receiver. The lower controls (l to r) are gain, regeneration, bandswitch, antenna trim, oscillation push button and frequency trim.

This RBL-5 was acquired from a ham neighbor here in Virginia City. It required a little work before it was functioning to its specifications. The tubular antenna connection input that attaches to the box that bolts to the back of the cabinet was shorted internally so essentially whatever antenna was connected was shorted to chassis. Removal of the tubular connector and just running the coax through the box directly to the antenna and ground terminals fixed the problem. Also, there was a soldering job at the audio output transformer that was poorly done. Exactly what the object of the solder job was is not known but it probably was in search of the lack of output that was really caused by the shorted antenna input. Fortunately, no original parts were removed and only the connections to the audio output transformer were moved to incorrect terminals. We just returned everything to the original connections and then the receiver output returned to normal.


photo left: The chassis on this RBL-5 is immaculate and all original. RF section is on the right side of the chassis and the power supply, limiter and audio sections are on the left side.


I have logged a lot of NDBs using this RBL-5 receiver, primarily because the RBL-5 is easy to use, very sensitive, has direct frequency readout and the limiter functions quite well. The limiter makes long sessions of receiving comfortable since the static crashes are reduced to the point where they aren't causing headaches anymore. I take the audio output right from the earphone jack on the front panel running 600 ohm 'phones for best copy on weak signals. The NBDs normally copied are multiple stations operating on the same frequency, with two and sometimes three different CW identifications being heard simultaneously. Using the RF trimmer and the Antenna Compensator controls, it is usually possible to enhance one or the other of the MCW signals and identify the particular NDB, (the RAK and RAZ LW receivers also have this ability to manipulate the signal a little to enhance copy.) The RBL works particularly well with the tuned loop antenna and this provides the ability to add some directional characteristics to the reception. Additionally, the loop can be slightly de-tuned to allow enhancing NDBs that are on one side or the other of antenna resonance which can sometimes help with copy.




photo right: The underside of the RBL-5 is also immaculate and all original. The photo shows the multiple gears that drive the two ceramic bandswitches. Construction is first rate as expected from National Company. Note that the alignment trimmers are all clustered together. The bottom cover has a sliding access panel that allows the receiver to be aligned with the bottom cover installed - probably why the RBL-5 has such an accurate dial readout.

Shown in the photos right and left is the Wells-Gardner Co. version, the RBL-3. This receiver is also in excellent condition. Note the difference in the transformers and chokes used in the W-G version compared to the National RBL-5. Typically, W-G used mostly National parts but did use their own transformers, chokes and smaller components. Note the rectifier tube in the upper left corner is a 5U4G rather than the 5Y3GT used in later versions of the RBL.  Performance of the W-G RBL-3 is the same as the National RBL-5.



RCA-Federal Telephone & Radio Corporation



CFT-46154, RBA-1
MW, LF & VLF Table Top Radio Receiver - 1941 contract
SN: 972     Accepted by USN 6-26-1943

CFT-46300, RBA-6 -
MW, LF & VLF Rack Mount Radio Receiver - 1945 contract
SN: 181   No Acceptance Tag

15kc to 600kc



1943 RBA-1 CFT-46154

In the late thirties, it was becoming apparent that a replacement receiver was going to be necessary for the aging series of longwave receivers used by the Navy at that time. The receivers included the RAA superhet from 1931, the RAG TRF from 1933, the RAK TRF with regenerative detector from 1935 and the various upgraded versions of these receivers that were built on later contracts. The new LW receiver design was going to blend the advantages of the TRF plus tracking BFO design of the RAG receiver but built with modern circuits. Using a TRF with tracking BFO was advantageous in keeping the leakage radiation on the antenna to a very low level that prevented enemy direction finding equipment from determining the location of the receiver. Additionally, the low-level of radiation allowed the receiver to operate in the presence of other receiving and transmitting equipment along with radar equipment without interference. The tracking BFO design utilized a section of the main tuning condenser so the BFO tuning condenser was ganged to the main tuning. Since the new receiver was not a superheterodyne, the BFO had to track at 1kc above the tuned frequency allowing a 1kc heterodyne to be heard thus allowing CW to be readily copied. There were a couple of very good reasons for not designing the new LF receiver as a superheterodyne. First, was to provide complete coverage of the tuning range of 15kc to 600kc. Most IF amplifier sections utilized around 400kc to 500kc for the intermediate frequency, right in the middle of the most used portion of the medium wave band (as far as the Navy was concerned.) Operation of the IF amplifier at, for example 455kc, would eliminate a section of frequency coverage of about 20kc either side of the intermediate frequency. Some superhet LW receivers moved the IF above the intended tuning range (15kc to 600kc) but there were disadvantages to this solution to the problem. For example, the RBH receiver uses an IF of 1500kc but any transmitting activity around 1500kc will "leak into" the IF section of the receiver and cause heterodynes throughout the tuning ranges.

At $3000 each cost to the Navy, the new RBA receiver was certainly an expensive receiver but a look inside reveals the incredibly high level of electro-mechanical design and construction. The tuning range is from 15kc up to 600kc in four bands. The illuminated dial readout is direct in kilocycles along with a logging scale that uses two scales - one on the main dial and a separate "units" logging scale. The mechanics of the tuning system design allows for super-smooth operation. The Gain adjustment controls the RF stage sensitivity of the receiver but there is also a "tracking" gain control (also called the auxiliary gain control) that is in series with the Gain control but geared to the main tuning. This allowed a variable gain compensation to frequency tuned that provided a constant gain level across the tuning range of each band. To protect the operator's ears, since most operation would be via earphones, an Output Limiter circuit allows an adjustment of the maximum output of the receiver based on the setting of the Output Level control. The O.L. can be switched on or off via a toggle switch on the front panel. The O.L. could be used in high level static conditions or for unexpectedly strong local signals. Two meters are provided, one to monitor Audio Output Level in db and one to monitor the B+ voltage.  Two levels of audio selectivity are provided, Broad selectivity rolls off the audio response at about 1300hz with an internal LP filter and the Sharp position is provided by a 1kc bandpass filter for CW in noisy conditions or in cases of interference. Voice modulated signals sound somewhat "muffled" due to the 1300hz roll off but the only voice signals encountered anymore will be from 530kc up to 600kc (bottom of the standard AM BC band.) Below 530kc, all signals are either data streams, MCW, MSK or other types of coded signals (unless hams are ever allowed to use 600M or 2200M.) The audio output is 600 ohms Z and is intended for earphones although the RBA can drive a matched loud speaker if necessary. The audio Z can be anything from 30 Z ohms up to 600 Z ohms. Negative feedback is utilized in the last two audio stages to reduce level changes as multiple earphones were added to the output (up to 20 sets of 600Z phones could be operated by a single RBA receiver.)

1945 RBA-6, CFT-46300 - The RBA-6 came from the factory painted Navy Gray and in a rack mount cabinet.

The separate power supply is the CRV-20130, which is the same power supply used for the 15 tube RBB and RBC superheterodyne receivers. The CRV-20130 provides the filament voltage and B+ requirements via an armored cable with heavy-duty connectors. The power supply will easily operate two RBA receivers for emergency conditions and two separate connectors are provided. The power supply has a cold-cathode regulator tube (OC3) and a HV rectifier (5U4.) The RBA uses eight tubes, three 6SK7 RF amplifiers, one 6J5 Triode Detector, one 6SK7 BFO, two 6SJ7 AF amplifiers and one 6K6 AF Output. Table top versions of the RBA receiver were identified as C(FT)-46154 (FT would indicate that Federal Tele. & Radio Corp. was the contractor) and CFT-46154-A (RBA-5) while the rack mount versions are identified as CFT-46300. Internally, all versions of the RBA receiver circuit are the same.

 photo left: Inside the RBA-6 receiver showing the top of the chassis. All of the TRF coils are in the cylindrical shielded cans to the left. The moveable covers on top of the cans allow access to the trimmers for alignment. The two front coils are for the tracking BFO. Note the gear-driven potentiometer coupled to the main tuning. This is the auxiliary gain control that allows for constant gain across the tuning ranges. Also note the shielded meters. The blue "dots" on the tops of the tubes are my indicators that I have tested these tubes and they are in good operational condition.



 photo right: The underside of the RBA-6 chassis. Full shielding of each RF section is provided when the bottom cover is installed. The heavy-duty band switch uses ceramic mounts with .25" silver-plated contact buttons. All components are mounted on terminal boards or are mounted directly to the chassis. Tracking BFO is the front section of coils. RF3, RF2 and RF1 are next going towards the rear. The rear-most set of coils are the Antenna Input coils.

The RBA-6 shown is from a 1945 contract. This version is identical to the RBA-5 internally but the RBA-6 is a rack mounted configuration only and is painted smooth Navy gray rather than black wrinkle. Judging by the condition of this receiver, it is unlikely that it was ever put into service. It is all original except for the substitution of an SO-239 UHF connector in place of the Navy coax connector for the antenna input. The RBA-6 is an impressive performer with ample sensitivity, direct dial read-out with illumination and a tracking BFO rather than regenerative-autodyne detector. The tracking BFO actually works quite well for finding the carrier on weak NBDs. The dial accuracy is excellent and allows tuning the NDBs by frequency rather than constantly referring to charts or graphs. The LP filter does limit the audio frequency response on BC stations but not to the point where the voice is incomprehensible. The O.L. works quite well at limiting the maximum output (which is usually due to static bursts) while not distorting the signal. The RBA-6 is a first-class longwave receiver capable of receiving any of the signals found below 500kc if used in an RF-quiet area with an appropriate antenna.

RBA-6 Performance - I have been using this RBA-6 during the morning hours for late September through most of October 2009 and have found the receiver to be a phenomenal performer. I can usually separate LLD 353kc in Hawaii from local Reno AP NDB NO 351kc and this is using just a wire antenna and not relying on the directional characteristics of a loop antenna. That's amazing selectivity for a TRF receiver. I've probably tuned in well over 100 NDBs but so far only two were new copies and they were West Coast NDBs. The wire antenna I'm using is the 135' center-fed dipole with 43' of open feed line that is shorted together at the receiver antenna terminals. This antenna, while not really something I designed for LW, seems to work quite well with all of the LW receivers. Radio Rossii 279kc is received every morning coming in very strong - Russian LW station located on Sakhalin Island. JJY also can be received every morning on 40kc coming out of Japan. Noise is the only limitation on reception and for better noise reduction I have to run a loop antenna.

photo above: This USN radio op is listening to the RBA receiver and is ready to copy on the mill. Other equipment is the General Radio LR-1 Frequency Meter, the RBB and RBC receivers. This photo of the U.S.S. Mugford in 1946

January 21,2010 - I finally got the RBA-6 up to the top floor of the house where it can be used with the six-foot loop antenna. I had tried using the loop antenna in the basement but the concrete floor and the rock foundation were a serious detriment to the loop's performance. The top floor of the house is actually about 30 feet above ground level and allows the loop to function quite well even though it is located indoors. The performance of the RBA-6 on the loop is amazing. The signals just jump out of a fairly quite background noise level. Much quieter than running on the wire antenna. Most frequencies seem to have at least three NDBs active and by tuning the loop I can usually enhance one or the other to allow copy. Quite an improvement in performance.

November 7, 2013 - QTH is now Dayton, Nevada and the antenna is a 300 foot long end-fed wire up about 50 feet. This antenna works quite well with the RBA-6 although the noise level is probably higher than using the loop. However, the actual ambient noise level is so low in Dayton that the 300 ft wire seems to provide better signal levels than the loop ever did in Virginia City. More info to come,... Nov. 8, 2013 0615 PST tuned in JJY at 40kc, very loud signal.


RBA-1, CFT-46154 - I had the receiver shown to the left for a short time. It's the early table top version RBA-1, the CFT-46154. This particular RBA-1 has had a common Field Change Modification Contract installed that changes the toggle switches for Reception mode and Output Limiter to knob-type controls. There are additional changes internally. The B+ meter has been replaced on this receiver. Additionally, like many receivers that have gone through a field rebuild, the cabinet is black wrinkle (it is for an RBA-1) while the receiver's panel has been repainted gray. This RBA-1 was traded off in 2015.

RBA-1 CFT-46154 SN: 972  -  Restoration Log

I acquired RBA-1 CFT-46154 SN: 972 (shown to the right) from a fellow in Texas in October 2017. It was shipped to Nevada via UPS. No damage was sustained during transport. I purchased this particular RBA-1 because it was the first all-original, black wrinkle finish, complete example that I had ever come across. Most RBA receivers found around here look like the RBA-1 shown in the photo above. That is, most have the Field Change modifications and have been repainted gray. Not that SN: 972 didn't have problems. For example, the DB meter glass was cracked to several places. The meter, however, worked fine. Band switching from Band 1 to Band 2 was normal. To Band 3 felt rough, like fine gear teeth meshing and switching to Band 4 was stiff but it would switch. All toggle switches seemed to function okay. There was a little bit of dial drag on the logging dial which was slightly rubbing against the housing. Inside was very nice with all shields present. Some very minor corrosion in just a few locations - nothing serious. Even the antenna input was still the original Navy coax fitting. Cosmetically, the cabinet was very scratched up with quite a bit of paint missing, especially on the top. Front panel was very good with some minor blemishes and old touch-ups. The dial mask on Band 4 needs some attention as there are some "pin points" of corrosion present. All knobs were present but the spinner was missing from the tuning knob. The two nomenclature panels were in good condition. All tags were present and in good condition on both the panel and cabinet. The original tuning chart was present with NSS (WWII Radio Central USN, Annapolis, MD,) shown at 18kc.

This RBA-1 didn't come with the CVR-20130 power supply or the armored power cable. Fortunately, I had a spare 20130 and a spare cable to apply power to this receiver. Normally, I wouldn't apply power without a thorough check out first, but the seller told me he had the receiver operating, so there was some confidence that nothing serious was going to happen. I did check all of the tubes first and ended up replacing three. I had SN:972 out in the shop, so I connected my 275 ft CF dipole with the 77 ft of feed line shorted to act as the antenna. Upon power up and warm up, the receiver was receiving KTHO 590kc up a Lake Tahoe quite loud. I had a 600Z ohm modified LS-3 connected to the phone jack on the front panel. Further tuning had MOG 404kc, a NDB from Montegue, CA and FCH 344kc from Fresno, CA coming in strong. This was about 3PM, so no DX NDBs were heard.  However, when switching to Band 3 the output was nil, same for Band 2. Switching to Band 1 the receiver again had output. NAA on 24.0kc was strong but NLK on 24.8kc was extremely strong. NPM on 21.4kc was strong from Lualualei, Hawaii.>>>

photo above: RBA-1 SN: 972 "as received" Oct. 11, 2017. Note the bubble-wrapped tubes piled up on the RF coils. Some of the cabinet can be seen to the right. This photo was taken before the power-up test.
>>>  So, this RBA-1 is somewhat functional. The most serious problem is the non-operative Band 2 and Band 3, however since the receiver works on Bands 1 and 4, the problem is certainly in the RF stages ahead of the detector. Additionally, repairing the mechanical issues of the band switching "roughness" and logging dial drag will be necessary. The DB meter glass repair will be accomplished by replacing the entire housing - it's a Weston Type 506 and they're common. Finally, when fully functional, a complete alignment. Cosmetics will be necessary too but that looks to mainly consist of cleaning and touch-up.
Dismounting the Front Panel - This is an arduous task that is not well-described in the manual, at least in the NAVSHIPS 900,708 manual I have. In order to repair the logging dial drag, the rough feeling band switch and restore the dial mask, I had to access the cast metal housing that has the dial, the dial mask and the band switching inside. The only access to into this housing is from the front and the entire front panel has to be dismounted to even see the front of this housing. To get the front panel off I first removed all of the knobs. The ANT. COMP. and INPUT CLPG. control shafts needed to be removed by loosening the set screws at the flexible coupling for each control and withdrawing the shafts out the front panel. All controls that have panel nuts needed the nuts and washers removed. The bottom cover needed to be removed. Then the two chassis-withdrawal knobs needed to be removed. The meter covers needed to be removed so the meter leads could be disconnected. The meters can stay mounted to the panel. The tuning chart frame needed to be taken off. The screws underneath mount a resistor board to the rear of front panel and these screws had to be taken out. The PHONES jack nut has to be removed and the shield around the phone jack itself has to be dismounted by the four screws on the side of the chassis. The dress nuts and the hex nuts that mount the four toggle switches had to be removed. I had to dismount the housing around the logging dial. Underneath there are two set screws that mount the logging dial to the tuning shaft. I loosened the set screws to remove the logging dial. The spacer around the band switch shaft had to be removed. Now came the difficult part,...there were six screws across the front panel that secure the front panel directly to the chassis. These had nylock nuts on the inner chassis side. I had to use a 3/8" open end wrench to hold the nut while the screw was removed. Two nuts are difficult to access because of the harness prevents seeing the nut but it can be done by "feel." The four vertical screws on the left side also had nylock nuts to mount them. On the right side, two screws had nylock nuts and two had pem nuts. The pilot lamp assembly had a 5/8" nut on the back side. When loosened, then the red jewel front could be unscrewed and dismounted. Now the front panel could be removed. Photo right shows the RBA chassis with the panel removed. All removed parts were "bagged and tagged" in small plastic bags. This "bagging" method is extremely helpful to prevent loosing any parts and for easing reassembly.    Oct 16, 2017
Accessing the Dial Mask and Band Switching - With the front panel off, I could see the housing was a two-piece assembly. The front part of the housing was mounted with four screws. The next step is to remove the four screws and lock washers that mount the front cover of the housing. Now the front cover can be removed and this exposes the tuning dial and the band switch arced gear. The dial mask is mounted to the front cover. In addition to the dial mask there is also a gear on the back side of the mask that engages the band switch arced gear and actuates the band changing function. However, since the mask needed to be restored it had to be separated from the front cover. This required removal of the retaining collar that was mounted to the band switch shaft. The set screw wasn't a hex like all the other set screws had been. This set screw was a spline or Bristol-type. Also, just to make removal difficult, the collar was pinned to the shaft. This required driving out the securing pin with a proper size punch. If done correctly with the proper tool, the pin comes right out. The collar has to be placed on a large vise that has the jaws slightly open. With a long thin diameter punch, the pin can be driven out. The set screw was only to keep the collar in place while the pin hole was drilled and the pin driven in. It doesn't have much of a purpose now and was easy to loosen. This allowed the collar to be removed and the dial mask, band switch shaft and drive gear could be separated from the front cover.

Painting the Dial Mask - Once the dial mask was removed its condition seemed a little worse than I thought. The minor flecks of corrosion were numerous but most of them seemed to be around BAND 4. I removed the black paint with stripper and wiped everything down with denatured alcohol. I worked over the surface with steel wool to be sure it was smooth and no blemishes would show when repainted. I used Krylon Flat Black for the paint as the initial coat.

photo right : The dial mask/cover assembly removed exposes the dial and the arced band switch gear.

Restoring the Mask Nomenclature - Of course, painting the dial mask covered up the frequency band nomenclature. These letters and numbers are embossed so they are somewhat higher than the flat surface of the mask. To restore the nomenclature requires carefully removing the paint just from the top surface of the letters and numbers. I had to do the nomenclature recovery in two steps. After the initial paint in flat black, I used a special angled tool (that I made) that could hold a very small piece of 320 grit Al-Ox paper. This was used to carefully remove the paint just from the nomenclature. Of course, there was some slight scuffing and other minor blemishes that happened to the paint surrounding the nomenclature. The next step was to carefully cut masking tape pieces to exactly cover only the nomenclature. It sounds time-consuming but it only takes about 25 minutes to do. Next, I applied a coat of Satin Black, which is much darker black than flat black. When this paint had dried, I removed the masking tape. Now, only very small areas between the letters and numbers had the flat black paint showing. These areas were so small that I touched them up using a "ultra-fine point" Pilot pen with black ink. The entire mask was then wiped down with a clean cotton cloth to even out the paint surface. It sounds like a lot of work and it is fairly time-consuming but the results are worth the effort since the dial mask is quite visible, directly in front of you, on all bands, whenever you're using the receiver.     Oct 19, 2017

Dial Mask and Band Switch Reassembly - I put a small dab of grease on the mask shaft and installed into the front cover of the housing. The washer and collar were then installed onto the shaft and the collar pin installed. The spline set screw was tightened. The band switch was set on Band 2 so the mask was rotated to show Band 2 also. The front cover was carefully placed in position and moved slightly until the gears meshed while the mask remained showing Band 2 centered. The four screws were installed. The adjustment for the gear mesh clearance is accomplished by moving the front cover upwards (reduces mesh) and tightening the screws. Testing switching showed that the mesh was correct as the switching was ultra-smooth and not binding.

photo right: Dial mask after restoration

Front Panel Restoration - This is really just a thorough cleaning with a brass wire brush (suede shoe brush) and Glass Plus to remove all dirt, grime and cigarette residue. The original wrinkle finish is very tough and can take this type of cleaning but you can't be real aggressive. You just want to remove the dirt not the paint. The front panel had been stripped of all tags and the two dial covers. The silver (engraved) nomenclature needed substantial cleaning. The front panel must have been pretty dirty as it took about five cleanings until the paper towels didn't turn gray with dirt and stayed fairly white. After this many cleanings, the nomenclature was very legible now. Next is the touch-up. I've been using jet black nitrocellulose lacquer for the last year or so. This method replicates how the USN did "touch-ups" on equipment that was being repaired but was not in the depot for an echelon-type rebuild. The lacquer looks too dark when being applied but with the final wipe down with 10W machine oil, the jet black matches the original wrinkle paint color quite well. The touched-up front panel is shown to the right.   

DB Meter Repair - The meter glass was broken in this meter. Luckily, it was a Weston Type 506, which are very common meters. The mechanical zero mechanism on a 506 is mounted in the glass making replacement glass difficult, if not impossible. The easiest method is to find a similar 506 meter that has the meter case with mounting flange. It doesn't matter what the meter scale is,...all I wanted was the metal case front with the glass. I dug around in the junk boxes and found a good candidate. The swap of the cases is easy only requiring removal of the three mounting screws on each meter, aligning the meter zero adjuster-pin with the adjustment slot while sliding the new housing glass in place and then reinstalling the screws. The only difference in the meter I used was that the glass was standard while the original USN meter glass had a "non-glare" treatment. Other than that, the transplant was perfect.      Oct 20, 2017

Plastic Used in Logging Dial Window and Tuning Chart Cover - These transparent plastic pieces are made of a celluloid-type of plastic that is very sensitive to water. Just plain old H2O will "fog" the plastic. The more water added, the worse the fogging gets. With enough water, the surface of the plastic will begin to dissolve. The only way to clean the plastic used in the Logging Dial cover and the plastic used for the Tuning Chart cover is to use oil. I used 10W machine oil (3 in 1 oil, actually.) The oil cleaned the plastic surface and didn't cause any change in the transparency. Another note on the Logging Dial window, if this piece is dismounted only leave it dismounted for enough time to clean it and the dial housing. This plastic piece is fairly thick and if not secured by mounting screws it will quickly begin to warp. I noticed the warp starting in about 15 minutes, so I remounted the plastic to allow it to retain its proper shape. Front Panel Remount - I had to touch-up all of the panel mounting screws with black lacquer. Several were missing all of their paint but most just had chips of missing paint. I mounted the two meters after I had touched-up their mounting screws (and washers.) The most difficult part of the front panel remounting is installing the two chassis shims. These two pieces are mounted by the six horizontal chassis screws. I had to have the six screws protruding thru their respective panel holes to hold the two shims in place while I guided the front panel into the proper position to fully seat against the chassis and the side panels. I also had to guide the four toggle switches along with the Gain control and the Output Level control thru their respective panel holes in order for the panel to fully seat. Once the panel is seated all of the other panel screws were installed. All but two of the panel to chassis mounting screws have nylock nuts that complicate the panel installation, especially the six horizontal chassis screws that have four of the nuts difficult to access with a wrench. I first installed the other panel screws and nuts but didn't fully tighten them. They were holding the panel in place but allowed for minor movement. For the six horizontal screws, the easiest method was to have the receiver upside down as this allowed the best view of where the nuts had to go. Once the nuts were installed I still didn't fully tighten the screws yet. I still had to install the screws that mounted the chassis withdrawal knobs. Once I had all of the panel mounting screws and nuts installed and threaded together, then I could go ahead and tightened all of the panel screws.

Each toggle switch had an flat washer, a hex nut and a dress nut for their mounting. The switches and two controls use external star locking washers that are mounted on the back side of the panel and flat washers and hex nuts are used on the front. The phone jack uses a special fiber insulator that has a locating pin that has to be inserted into the mating hole in the back of the panel. The phone jack body front just fits into the recessed channel which keeps the phone jack from turning when the panel nut is tightened. I had to make sure that two fiber washers and one metal dress washer were used when installing the phone jack nut. This was to provide the correct chassis insulation and the proper spacing so the phone jack nut would tighten up.

Reassembly Notes - When I installed the metal spacer for the band switch shaft I had to make sure that the spring washer was mounted on the band switch shaft with the "fingers" facing up so it pressed against the recessed area behind the spacer. This spring provides a thrust load on the band switch shaft. When installing the logging dial, it also had a spring that mounted on the tuning shaft and loaded the logging dial. To synchronize the logging dial, I first had to set the main tuning to the minimum frequency on any band. I noted that the logging scale actually is a little longer than the tuning scales but I had to set the main dial to "0" on its logging scale. I then installed the logging dial on the tuning shaft with the load spring in place. I set the logging dial to read "0" on its scale and pressed the logging dial firmly as far back onto the shaft to load the spring and then tightened the set screws. I installed the logging dial cover and checked the operation for any rubbing or binding while tuning. I also checked that each 100s segments on the main dial's logging scale matched the logging dial at "0" or within a couple of divisions of "0." I then installed the meter covers and then cleaned and installed the knobs.

I was pretty sure that during reassembly, with tightening up the panel screws and the other mounting screws, some paint chips were going to "pop off." I ended up with two fairly large chips and several smaller chips. These were touched up with black lacquer.

With everything back in place, retesting and troubleshooting the Band 2 and Band 3 problems could begin.    Oct 22, 2017

Minor Troubleshooting - Problem one was with the DC Voltmeter reading very low. Pressing on the meter face gently would result in the voltage reading going up to normal, +220vdc. The problem was that I just reinstalled the lug connections and didn't clean them first. Cleaning with a brass wire brush got the terminals and lugs clean and when reassembled, the voltage reading was normal.

Problem two was that the ANT. COMP. control wasn't indicating the air variable position correctly. The ANT. INPUT shield has to be removed (easy to do - only four screws) to see the plates of the condenser. I set the condenser per the manual,...full mesh is 10 to the right side of the scale. There's a rotation limiting pin on the extension shaft thru the front panel that only allows 180 deg. of rotation so the air variable position has to match the panel scale.

On to the serious problems,...

Repairing Split Hex-Collars on Air Variable Trimmer Capacitors - So far, the problems had been minor stuff. I was now going to find out why Band 2 and Band 3 were inoperative. I could hear a few signals on Band 3 but they were very weak. Band 2 was dead. I used a RF Signal Generator to inject a RMS voltage into the Antenna Input to act as a steady, high-level signal. When adjusting the trimmers to resonate the RF coils, the problem became "painfully" obvious,...on Band 2, two of the air variable trimmers had split hex-collars and the trimmer rotor had dropped down and was "shorting" the rotor to stator plates which shorts the RF coil which in turn takes the grid of that RF amplifier tube to ground. I adjusted the rotors until they were fully un-meshed which removes the short circuit but leaves that RF coil "not tuned" and the rotor too low to mesh with the stator. Enough signal leaks thru to tell that these are the defective components keeping Band 2 from operating. I found that Band 3 had one split hex-collar trimmer that was already un-meshed. This was why Band 3 seemed to work but had weak signals. Only Band 1 and Band 4 had all good trimmers.

The repair of these split hex-collar trimmers requires the removal of the defective RF coil assemblies. First remove the shield-can by removing the top nylock nut and the four screws at the base of the shield. Removal of the actual RF coil assembly can be fairly difficult due to the 16 gauge buss wire used for connections. This requires a fairly large soldering iron (or gun, I used a Weller 250W gun.) On most of the buss connections the wire is wrapped a half turn around the terminal. On some wires, the joint can be heated and the buss wire lifted off of the terminal with large needle nose pliers. Other joints may require the use of a small pointed tool (like a small awl) to get the buss wire bend started once the solder was molten. At this point, long needle nose pliers can slightly unwrap the buss wire from the terminal and then it can be lifted off of the terminal. There are four buss wires and two stranded wires per coil assembly that need to be removed. Once desoldered, then the nylock nuts can be taken off and the coil assembly removed. Be careful when doing the reinstallation of the buss wire onto the terminals. If the buss wire was unwrapped too much it may break when bending it back into position. Try to only unbend the buss wire slightly when removing and then no problems should be encountered when reinstalling.

photo above
: The hex-collar on the right is correct and not split. The hex-collar on the left is split and has been taken off to show the trimmer rotor shaft.

photo above:   Cardboard shims are installed between the rotor and stator plates to maintain proper spacing for repair

An ideal hex-collar repair would require access to a machine shop to make a new hex-collar from 1/4" brass hex stock. The shaft on the trimmer condenser is slightly tapered from 0.152" up to 0.154" and this requires that the hex stock have a slight taper also. The height of the collar is also important since the press fitting of the collar will stop when the adjusting slot of the rotor is at the top of the collar. This fit then has to result in the proper spacing of the rotor and stator plates. Original dimension for the height of the hex-collar was ~0.190" and the new collar would also have this same dimension. The final measuring involves having the hole perpendicular to the top and bottom surfaces of the hex-collar to allow even movement of the adjustment without binding. This type of repair is impractical for most restorers because we don't have access to a machine shop. The next repair method described doesn't require any special tools.

An easier repair of the split hex-collar is to use solder to hold the hex-collar in place with the proper spacing for the trimmer plates. Cardboard shim stock installed between the rotor and stator bottom plates will provide a firm stationary spacing for the plates. A minimum of four shims should be used for best support of the rotor plates. I used .022" thick cardboard that can be salvaged from small boxes or the cardboard backing from tablets or from many other sources. As long as the shim thickness is about .022" the plate spacing will be correct.

The first step is to remove the RF coil assembly from the receiver. I've tried to do this repair with the coil assembly in place (just the shield-can removed) and it is almost impossible to get the cardboard shims installed. There's just not enough space for access and there's limited visibility, making the whole operation impossible. Although it's difficult to unsolder the 16 gauge buss wiring to remove the RF coil assembly, it's easier than trying to do this procedure with the coil assembly still mounted in the receiver.

Once the RF coil is removed, installing the shims is easy. I use a pair of channel locks to gently lift the rotor (with the hex collar installed so it will only move just high enough.) I then slide in four shims. Now, release the channel locks and remove the hex-collar. The slotted end shaft will be at the correct height (for the hex-collar to be sweat-soldered in place.) The slotted end of the shaft has to be cleaned with a small jeweler's file but don't clean all the way down to the stationary spacer. Just the upper half of the shaft should be cleaned. Add some slight grooves with the file for the solder to adhere to better. The inside of the split hex-collar must also be cleaned with the small file.

I used a large soldering iron to "tin" the slotted shaft (250W Weller.) If the hex-collar now won't fit on the shaft then file off some of the solder until the hex-collar does fit entirely onto the shaft with the bottom of the hex-collar flush with the stationary spacer. Heat the hex-collar and shaft with the soldering iron until it's hot enough that a very small amount of solder can be melted. This solder will be wicked between the hex-collar and the shaft and should provide a very strong bond. Add a little more solder to the top slot area and create a slight solder "dome" on the top. Let the solder cool and remove the shims.

I used a Dremel tool with a small cut-off wheel to make a slot in the solder. This slot has to be widened by gently using a hacksaw blade (blade alone - not the entire hacksaw.) Test the trimmer rotation using a blade screw driver. It should now adjust correctly. Check all of the wires and components on the RF coil assembly to make sure there's been no damage during the repair. If it looks okay, then reinstall the RF coil assembly into the receiver.  Oct 27, 2017

photo right:   Finished hex-collar repair showing the slot cut to allow adjustment of the trimmer when RF coil is fully assembled.

Another Problem with Band 3 - Band 2 was performing very well after repairing the two defective trimmers. However, Band 3 still seemed to be lacking sensitivity. Injecting a modulated signal into the Antenna Input revealed that the RF trimmers were all working correctly on Band 3. Switching off the modulation and switching to CW (BFO on) should have resulted in a heterodyne signal but no change was noted in the signal. I adjusted the frequency to the top end of Band 3 (sig gen and receiver) and adjusted the BFO trimmer and what happened wasn't unexpected. Of course, the trimmer rotor dropped as soon as it was unmeshed. The non-operational BFO had seemingly reduced the sensitivity because no signals could be demodulated. To repair the BFO on Band 3 is very similar to repairing the split hex-collars on the RF coils since it's exactly the same type of trimmer.   >>> >>>   The BFO coil assembly for Band 3 and Band 4 was removed from the receiver. The trimmer was repaired per the procedure shown above. After the BFO assembly was reinstalled, the BFO didn't work on either Band 3 or Band 4. This could only have been caused by the common return for both trimmer capacitors. I ended up removing the BFO coil assembly again, just to check it over closely. I found a questionable solder joint on the common buss wire return that looked like it might have been cracked but that should have only affected Band 3. Before I reinstalled the coil assembly, I carefully resoldered all of the coil wire wraps to the terminals as a precaution. I installed the coil assembly and soldered the four buss wire connections and the stranded wire return connection. Upon testing, both BFOs worked. The problem was probably due to the coil wire wraps around the terminals as these looked like questionable solder joints. The shield cover was installed and then the BFOs adjusted for 1kc above the tuned frequency on Band 3 and Band 4.         Oct 29, 2017
Trimmer Capacitors Split Hex-collars -  Notes - This splitting of the hex-collar on this style of trimmer condenser is fairly common. This type of trimmer was very popular in the mid-thirties up into the mid-forties. They're found in Hammarlund Super-Pro receivers, all BC-348 receivers other than Q, N and J versions, Navy RBB and RBC receivers, on and on. It's likely the problem is due to poor storage conditions and metal fatigue due to age. When the metal was new the hex-collar could expand and contract with varying temperature cycles. However, years and years of thermal cycling will cause the metal to become brittle and eventually it will crack. Poor storage in garages or sheds only results in thermal cycles that are even more extreme and rapidly cause the metal to become brittle. There isn't much that can be done today except to repair the trimmers as they are encountered.
Alignment - The hex-collar trimmer repairs resulted in the RBA-1 now being fully functional. The receiver requires a specific "dummy antenna" to load the input regardless of the impedance of the signal generator. Luckily, the schematic of the "dummy antenna" is included in the NAVSHIPS manual. The parts required are one 20uH inductor, one 400 ohm carbon resistor, one 200pf capacitor and one 400pf capacitor. The schematic is shown to the right.

The trimmers are all adjusted at the top end of each band. For example, on Band 4, set signal generator to 600kc. Set receiver to 600kc. With signal input to antenna input thru dummy antenna, adjust all Band 4 trimmers for maximum deflection of the DB meter. Reduce the GAIN control to compensate as the signal level increases. Use lowest signal input that gives an indication on the DB meter set at the lowest scaling. This is repeated for each band.

The BFO is aligned at the top end and the bottom end of each band. With 600kc unmodulated input and receiver tuned to 600kc, switch on BFO. A 1kc heterodyne should be heard. Adjust BFO 4 trimmer to 1kc heterodyne, if necessary. Tune to 235kc and set generator to 235kc. A 1kc heterodyne should be heard.   >>>

>>>   There are adjustments for the BFO inductance for each band that are "thru the front panel." Two holes are under the tuning chart (Left = BFO 3 and Right = BFO 1) and the two other holes have acorn head screw plugs that are removed to access the holes (Left = BFO 4 and Right = BFO 2.) Adjust BFO 4 inductance for a 1kc heterodyne, if necessary. Check both the upper and the lower frequencies to verify that the BFO is actually 1kc higher than the tuned frequency. Tune the receiver up about 1kc higher in frequency and the BFO should be zero beat if it is set 1kc higher than the tuned frequency. Repeat the adjustments until BFO tracks. Repeat the procedure for each band.
Is the Dummy Antenna Really Necessary? - When the RBA-1 was in service and being aligned at a USN depot, it was unknown to the radio repair technicians what type of antenna was going to be connected to the receiver. Shipboard antennae were quite different from USN land station antennae. What the Dummy Antenna does is provide a somewhat constant impedance load to the receiver that behaves more like a typical antenna would than a direct connection to the Signal Generator output would. The variability of what type of signal generator was used probably also entered into the alignment problems. Using the Dummy Antenna generally ensured that every RBA would come thru alignment with the same performance specification regardless of where it was going and what type of antenna it was going to be used with. Today, most of us are going to use one specific antenna with the receiver. If it's an end-fed wire of considerable length, it might be better to align the receiver with this antenna connected. Couple a signal generator output to the receiver's antenna input by using a small "antenna" on the signal generator output consisting of a three foot wire that's near the receiver. This will provide a frequency specific signal that can be adjusted for amplitude, frequency and modulation (if needed.) This simulates the receiver actually "picking up" a transmitted signal and aligning the receiver for the best operation with the antenna the is going to be used. In this type of set-up, the load of the antenna is just as it is when the receiver is in operation. This then provides an alignment that is exactly for the actual antenna that is going to be used. Tuned loops are a bit more difficult and experimentation would probably be best with these types of antennae. Usually, the loop can be tuned for the highest frequency on the band and then the receiver aligned to that impedance load. Since there is no alignment adjustment for the low end of the band, check to see if when the loop and the receiver are tuned to the low end of the band that the performance is the same as the upper end. When experimenting with various antennae and alignment, only the antenna coils will be affected and only those coils will require adjusting.
Cabinet Restoration - I really didn't want to do an entire respray of the cabinet. If I did, it wouldn't match the receiver front panel. There was a lot of paint missing, especially on the top. The first step was to remove the two data plates and then to clean the cabinet's remaining paint with a brass wire brush and Glass Plus. I then used black nitrocellulose lacquer to repaint all of the areas that were bare metal. I let this set for a day. The next step was to mix a very thin batch of lacquer and thinner - about 2:1 ratio. With gloves on, I then used a cotton pad saturated in thinned lacquer to "go-over" the entire cabinet. This hides the "touch-ups" and ends up with the cabinet looking in good original (although "touched-up") condition. I then reinstalled the data plates and installed the receiver into the cabinet.  Antenna Connection to Navy Coax Fitting - These Navy coax fittings are not common making them difficult to find. There are two easy ways to connect an antenna feed line to the RBA (or the RBB or RBC) that allow use of coaxial cable and provide a good connection to the receiver. Use a double female SO-239 adaptor. The outer diameter will just fit into the Navy coax barrel. It will slightly "thread" itself and make good electrical contact. However the pin at the bottom of the Navy fitting is too far away to make positive contact with the center conductor of the SO-239 adapter. I usually roll .010" thick brass or copper sheet metal into a tube. The tube can then be inserted into the SO-239 adapter center barrel. The other end of the tube should be about a .375" extension and the open end of it will fit over the Navy center conductor pin.

Another way to connect coax is to use a female banana pin plug (these do fit onto the Navy center conductor pin.) The coax center conductor can be soldered to the female banana plug. The shield can have a drain wire soldered to it and it can be connected to the ground lug on the back of the RBA cabinet. 

Performance - Since I had the RBA-1 set up out in the shop, I had to use the 270 foot long, center fed dipole. Since the antenna is fed with open transmission line, I just disconnected the two wires from the antenna coupler and, using clip leads, shorted them together and then used a single 14 gauge stranded wire to connect the feed line to the receiver. Perhaps this acts like a large "T" antenna that has the 77 feet of feed line acting somewhat as a vertical with a large 270 foot long "top hat." The "T" configuration was a popular antenna during the early days of radio.

During some of my initial testing and troubleshooting I tuned in BO 359kc, the NDB from Boise, Idaho - and this was during the day! Quite a surprise,...but when I aligned Band 3 to the antenna, I tuned in HDN 211kc in Gooding , ID, HLE 220kc in Hailey, ID and TCY 204kc in Tracy, CA - during mid-day! Additionally, the normal daytime copy of FCH 344kc in Fresno, CA, MOG 404kc in Montague, CA and CC 335kc in Concord, CA were all present. None of these were newly copied NDBs but I've never heard BO, HLE, HDN or TCY during the day. The next day, I tuned in DC 326kc in Princeton, BC, Canada. Incredible! This was at 13:30 in the afternoon and I was hearing British Columbia. Another note, these stations were being copied on loudspeaker, not 'phones. More experimenting with other LW receivers will be necessary to determine if this is RBA-1 performance (unlikely) or if it's antenna performance (likely.)

Other daytime copies included the USN MSK stations NLK 24.8kc in Jim Creek, WA, NAA 24.0kc in Cuttler, ME, NPM 21.4kc in Lualualei, HI and, although substantially weaker, HOLT 19.8kc in Exmouth, Australia. These are very strong stations that are easy copy, day or night.

The INPUT CLPG and ANT COMP. controls are very important and must be adjusted for each band. In fact, the ANT COMP. should be peaked every 10kc or so.

The OUTPUT control and OL switch are used as an audio AVC. Once set, the audio output won't increase beyond the level set. When there's a lot of static crashes or "popping" noises, the OUTPUT (limiter) control helps keep your ear drums intact when using 'phones.    Nov 1, 2017

The following is a log of the stations tuned with the RBA-1 using the 270' CF with 77' of ladder line with wires shorted together. There are six listening sessions within about a seven week period that include both daytime and nighttime listening periods. With the six sessions, I tuned in 100 different NDBs of which six were newly heard stations. Greatest DX was DDP 391kc in Puerto Rico which isn't unexpected since it runs 2KW. Other DX (for a western US location) was FIS 332kc in Key West, FL, YMW 366kc in Maniwaki, Quebec and DB 341kc in Burwash Landing, Yukon. Daytime copy of British Columbia stations YZA 236kc and DC 326kc was unexpected but was certainly due to the time of year. Best LW reception is usually in November and December. The large antenna was probably also a factor. Maybe the RBA-1 was a factor, too.

RBA-1, CFT-46154, SN: 972   NDB Log

Antenna is 270' CF with 77' ladder line with feedline wires tied together.   Height is 40 feet.   Stations are listed in "as heard" order.   Pacific Time.   Newly Heard NDBs - Blue with asterisk. Unless otherwise indicated, all reception is using 600Z ohm 'phones as audio reproducers.

Nov. 3, 2017  05:55-06:35 - Cndx Xlnt, Quiet

Nov. 9, 2017 19:10-19:40 - Cndx Poor, Noisy

Nov. 18, 2017  13:30 - Cndx Xlnt

Dec 23, 2017 19:05-19:50 Cndx Xlnt

1. UAB -200kc - Anahim Lake, BC, CAN
2. IP - 201kc - Mobile, AZ
3. YBL - 203kc - Campbell River, BC, CAN
4. TCY - 204kc - Tracy, CA
5. HDG - 211kc - Gooding, ID
6. LU - 213kc - Abbottsford, BC, CAN
7. QU - 221kc - Grand Prairie, AB, CAN  *
8. HLE - 221kc - Hailey, ID
9. YKA - 223kc - Kamloops, BC, CAN
10. LWG - 225kc - Corvallis, OR  *
11. CG - 227kc - Castlegar, BC, CAN
12. VG - 230kc - Vermillion, MB, CAN  *
13. OKS - 233kc - Oshkosh, NE
14. BR - 233kc - Brandon, MB, CAN
15. OJ - 240kc - High Level, AB, CAN
16. AVQ - 245kc - Tucson, AZ
17. YCD - 251kc - Vancouver Is., BC, CAN
18. LW - 257kc - Kelowna, BC, CAN
19. HCY - 257kc - Cowley, WY
20. SLE - 266kc - Salem, OR
21. YK - 269kc - Castlegar, BC, CAN
22. XS - 272kc - Prince George, BC, CAN
23. GYZ - 280kc - Guernsey, WY - USCG
24. CEP - 278kc - Ruidoso, NM
25 QD - 284kc - The Pas, MB, CAN
26. EKS - 286kc - Ennis, MT
27. YYF - 290kc - Penticton, BC, CAN
28. TOR - 293kc - Torrington, WY  *
29. TV - 299kc - Turner Valley, AB, CAN
30. ONO - 305kc - Ontario, OR
31. UNT - 312kc - Penticton, BC, CAN  *
32. DC - 326kc - Princeton, BC, CAN
33. POA - 332kc - Hilo, HI
34. RYN - 338kc - Tucson, AZ
35. ZU - 338kc - Whitecourt, BC, CAN
36. DB - 341kc - Burwash Landing, YK, CAN
37. BKU - 344kc - Baker, MT
38. FCH - 344kc - Fresno, CA
39. SBX - 347kc - Shelby, MT
40. NY - 350kc - Enderby, BC, CAN
41. AL - 353kc - Trina, WA
42. MEF - 356kc - Medford, OR
43. BO - 359kc - Boise, ID
44. YQZ - 359kc - Quesnel, BC, CAN
45. RPX - 362kc - Roundup, MT
46. 6T - 362kc - Foremost, AB, CAN
47. DPY - 365kc - Deer Park, WA

WH2XVN copied on 183kc at 05:57

1. ZQ - 410kc - Sir Wilfred Laurier CCGS, BC, CAN
2. MW - 408kc - Moses Lake, WA
3. MOG - 404kc - Montegue, CA
4. QQ - 400kc - Comox, Vancouver Is, BC, CAN
5. SB - 397kc - San Bernardino, CA
6. ULS - 395kc - Ulysses, KS
7. DDP - 391kc - San Juan, Puerto Rico
8. YWB - 389kc - West Bank, BC, CAN
9. JW - 388kc - Pigeon Lake, AB, CAN
10. WL - 385kc - Williams Lake, BC, CAN
11. PI - 383kc - Tyhee, ID
12. GC - 380kc - Gillette, WY
13. OT - 378kc - Bend, OR
14. EHA - 377kc - Elkhart, KS
15. EX - 374kc - Kelowna, BC, CAN
16. LV - 374kc - Livermore, CA
17. MF - 373kc - Rogue Valley, OR
18. HQG - 365kc - Hugoton, KS
19. DPY - 365kc - Deer Park, WA (2nd copy)
20. RPX - 362kc - Roundup, MT (2nd copy)
21. BBD - 380kc - Brady, TX
22. AP - 378kc - Active Pass, BC, CAN
23. MR - 385kc - Monterey, CA
24. HAU - 386kc - Helena, MT
25. CSB - 389kc - Cambridge, NE
26. PNA - 392kc - Pinedale, WY
27. DQ - 394kc - Dawson Creek, BC, CAN
28. FN - 400kc - Ft. Collins, CO

29. MM - 411kc - not on Navaid (MW w/o the dit?)
30. INUU - 395kc - I've copied this beacon many times but have never found it on any Navaid

NOTE:  Conditions were particularly noisy due to a passing storm front and wind causing severe antenna static. One of the problems with using an outdoor antenna. Even indoor loops will respond to weather fronts however.

 Nov. 17, 2017,  19:00 - Cndx Poor

1. FS - 245kc - Sioux Falls, SD
2. YZA - 236kc - Ashcroft, BC,CAN
3. XC - 242kc - Cranbrook, BC , CAN

High level of static from passing front. Static was so bad that OL didn't help. These are new copies for RBA-1 only.

As an illustration of how fast signal cndx can change, I was running the RBA-1 in the early afternoon on the loudspeaker. Copied for long time periods the following stations,...

1. HLE -221kc - Hailey, ID
2. HDG - 211kc - Gooding, ID
3. YZA - 236kc - Ashcroft, BC, CAN

The static level was very low and these stations were easy copy on loudspeaker. This was at 1:30PM in the early afternoon!

Nov. 22, 2017   21:10-21:40 - Cndx OK

1. LU - 213kc - Abbotsford, BC, CAN
2. RL - 218kc - Red Lake, ON, CAN - #
3. QU - 221kc - Grand Prairie, AB, CAN
4. YKA - 223kc - Kamloops, BC, CAN
5. DN - 225kc - Dauphin, MB, CAN - #
6. CG - 227kc - Castlegar, BC, CAN
7. VG - 230kc - Vermillion, MB, CAN
8. YZA - 236kc - Ashcroft, BC, CAN
9. AVQ - 245kc - Tucson, AZ
10. YCD - 251kc - Van. Is, BC, CAN
11. HCY - 257kc - Cowley, WY
12. LW - 257kc - Kelowna, BC, CAN
13. YK - 269kc - Castlegar, BC, CAN
14. GUY - 275kc - Guymon, OK - #
15. CEP - 278kc - Ruidoso, NM
16. YYF - 290kc - Penticton, BC, CAN
17. TOR - 293kc - Torrington, WY
18. ONO - 305kc - Ontario, OR
19. VC - 317kc - LaRonge, SK, CAN - #
20. MA - 326kc - Midland,TX - #
21. DC - 326kc - Princeton, BC, CAN

Static level was moderate even though weather and wind were calm. Most are repeat copy but five new stations to this receiver (marked with #.)

Total NDBs copied with this RBA-1 = 100

Total newly heard NDBs = 6
1. GDV - 410kc - Glendive, MT #
2. MW - 408kc- Moses Lake, WA
3. QQ - 400kc - Comox, BC, CAN
4. ENS - 400kc - Encenada, BCN, MEX #
5. FN - 400kc - Ft. Collins, CO
6. DQ - 394kc - Dawson Creek, BC, CAN
7. YWB - 389kc - West Bank, BC, CAN
8. WL - 385kc - Williams Lake, BC, CAN
9. HAU - 386kc - Helena, MT
10. YPW - 382kc-Powell River, BC,CAN#
11. GC - 380kc - Gillette, WY
12. K2 - 378kc -Olds-Didsbury, AB, CAN#
13. EX - 374kc - Kelowna, BC, CAN
14. YK - 371kc - Yakima, WA#
15. YBV - 370kc - Berens River,MB,CAN#
16. SX - 367kc - Cranbrook, BC, CAN#
17. YMW - 366kc - Maniwaki, QC, CAN#
18. HQG - 365kc - Hugoton, KS
19. AA - 365kc - Fargo, ND#
20. BF - 362kc - Nolla-Seattle, WA #
21. PTT - 356kc - Pratt, KS#
22. IN - 353kc - International Falls, MN #
23. PG - 353kc - Portage, MB, CAN #
24. SBX - 347kc - Shelby, MT
25. MNC - 348kc - Shelton, WA #
26. FCH - 342kc - Fresno, CA
27. RYN - 338kc - Tucson, AZ
28. LF - 336kc - LaSalle, MB, CAN *
29. FIS - 332kc - Key West, FL #
30. DC - 326kc - Princeton, BC, CAN
31. MA - 326kc - Midland, TX
32. YQF - 320kc - Red Deer, AB, CAN #
33. VC - 317kc - LaRonge, SK, CAN
34. YYF - 290kc - Penticton, BC, CAN
35. EKS - 286kc - Ennis, MT
36. CEP - 278kc - Ruidoso, NM
37. XS - 272kc - Prince George, BC, CAN
38. YK - 269kc - Castlegar, BC, CAN
39. ZSJ - 258kc - Sandy Lake, ON, CAN #
40. ZYC - 254kc - Calgary, AB, CAN #
41. YCD - 251kc - Vancouver Is.,BC, CAN
42. FS - 245kc - Sioux Falls, SD
43. YZA - 236kc - Ashcroft, BC, CAN
44. FOR - 236kc - Forsyth, MT

Xlnt cndx. One newly heard "LF 336kc" and 19 new copies for this receiver marked with #.

NAVY-RADIO.COM - For the most detailed information WWII Navy Longwave gear and on all types and all vintages of Navy LW radio equipment, Navy LW radio stations with vintage photographs - go to   Nick England's incredible Navy-Radio website has the most information available. 

Mackay Radio & Telegraph Company


  Marine Radio Receiver  Type 3001-A

Commercial MW, LF & VLF Shipboard Receiver

15kc  to  635kc 

Model Introduced in 1948    SN: 52-M-070 from 1952  

Mackay Radio & Telegraph Company was founded by Clarence Mackay, son of John W. Mackay, one of the "Big Four of the Comstock" fame in Virginia City, Nevada. However, by the time this Mackay Radio receiver Type 3001-A was produced, International Telephone & Telegraph Co. had owned Mackay Radio for a couple of decades. ITT continued to use the Mackay name in their marine radio equipment up until just recently, 2006.

The 3001-A is a Longwave regenerative receiver covering 15kc to 635kc in four bands and although the design dates from around 1948 this receiver was built in 1952. The 3001-A is an updated version of the WWII Mackay Type 128-A receiver. The 3001-A was mainly for commercial shipboard (non-military) use where it could be set up as the main receiver or as the emergency receiver. These receivers were sometimes installed into Mackay MRU-19/20 shipboard radio consoles - two 3001-A receivers were normally used in these set-ups along with transmitters and other auxiliary equipment. The 3001-As were panel mounted when installed in the MRU set-ups. The receiver uses an AC-DC circuit and can operate on 115vac or on batteries. Various filament battery options were available with 6vdc, 12vdc and 24vdc being the most popular. B+ was supplied by standard dry cell B batteries when used. The receiver uses a four pin Amperite ballast tube along with six octal tubes. The cabinet has "knock-outs" all along the back and the bottom-rear to allow routing the various cables necessary for the installation. These would consist of the Main Antenna and Auxillary Antenna, the AC power connections, the DC power connections and an external earphone connection. A small built-in speaker provides for radio room monitoring but earphones would normally have been used by the shipboard radio operator. These type of Mackay receivers were used onboard ship for decades (a few reports indicate that some may still be in use.)

photo left: Top of the chassis showing the Jones plugs that are for the power and signal inputs to the receiver. The large resistor is for operation on 12vdc for the filaments.





photo right: The under side of the chassis showing the various coils and other components. This receiver was partially re-capped sometime in the past.

This Mackay 3001-A was a ham swap meet find purchased in October, 2009. The design and construction of the Mackay 3001-A is obviously commercial and is no where near the "cost-no-object" designs and "over-built" construction that were used by the Navy. Still, the receiver is an impressive performer and has some interesting designs in the circuitry. Tubes used are 1 - 6SK7 RF Amplifier, 1-6J5 Detector, 2 - 6SJ7 AF Amplifiers, 1 - 6G6G Audio Output, 1 -35Z5GT Rectifier and 1 Amperite Ballast Tube. Interestingly, the detector input is also directly connected to the first AF amplifier since the 6J5 is acting like a diode. Each Detector coil has its own "tickler" winding which is routed back to the RF Amplifier's screen and is controlled by a 50K Regeneration pot. Selectivity is controlled by a combination of the RF Gain setting and the setting of the Regeneration - too much RF Gain results in very broad signals. Best performance is achieved using earphones with the AF Gain fully advanced and using only what RF Gain is necessary to hear the signal. Regeneration should be set just at the oscillation point or slightly into the oscillation range - which ever gives the best signal. The Antenna Trim will somewhat manipulate the signal tuning and can contribute to successful copy on very weak signals. The vernier reduction action of the main tuning dial seems a bit fast at first but in actual use the bandspread is wide enough that the tuning rate works out just fine. The 3001-A is a great little receiver (weight is only about 35 lbs) with excellent sensitivity and it is capable of receiving just about anything in the LW spectrum. Besides all of the normal NDBs, this 3001-A also has received the LW BC station from Sakhalin Island on 279kc and also JJY 's pulse-coded time signals from Japan on 40kc. The Navy NSRTTY station from Hawaii on 21kc and from Cutler, Maine on 24kc both can received quite well. An impressive receiver that doesn't challenge your back to move.

U.S. Army Signal Corps

Collins Radio Company




MW, LF, VLF  Double Conversion Superheterodyne

15kc to 1500kc


SN: 268  from 1951 Contract (1953 build date)


1953 R-389 SN: 268 installed in CY-979A Mobile Table Cabinet

Basic Description - Electronics - Built along some of the same lines as the famous R-390 receiver, the Collins R-389 is essentially the LF companion to the R-390 receiver, covering 15kc to 500kc in one tuning range and 500kc to 1500kc in the second tuning range. The R-389 uses very complex methods, both electronic and mechanical, to achieve its complete MW, LF and VLF coverage while still utilizing a 455kc IF. The receiver uses 36 tubes within five modules that interconnect and are mounted within the main frame. The 15kc to 500kc tuning range utilizes five permeability-tuned RF bands. The 500kc to 1500kc tuning range utilizes two permeability-tuned RF bands. The band switching is motor-driven and occurs seamlessly as the receiver is tuned from the lowest to the highest frequency within the two tuning ranges.

Two RF amplifiers are used and the first conversion mixes the incoming RF signal frequency with the VFO (470kc to 1955kc output f) plus the 10.455mc Crystal Oscillator (8.5mc to 9.985mc resulting f) to achieve a 10mc IF. The second conversion mixes the 10mc IF with the same 10.455mc Crystal Oscillator to achieve the 455kc IF. This double conversion scheme was to allow complete coverage from 15kc to 1500kc with no gaps in the frequency coverage. Additionally, since the two mixer stages are 180 degrees out of phase, any drift within the conversion mixers is cancelled leaving only the VFO drift. This is similar to how the "drift-cancelling" Wadley Loop operates.

From the second mixer circuit on, the R-389 utilizes the same modules that are found in the R-390. That would be the six-stage IF module, the two channel audio and electronic voltage regulator circuit module and the power supply module. Although the 70H-1 PTO (VFO) looks exactly like the one in the R-390, it's very different inside and tunes from 470kc to 1955kc.

Mechanical Details - The manual tuning of the receiver RF front end uses clutch-coupled gears to rotate the main RF tuning shaft that has worm gears that perpendicularly engage and rotate the gear-driven front and rear line shafts that have worm gears that in turn engage gear-driven vertical screw-shafts (cut with forward and reverse threads) that raise and lower the various slug racks. When this gear-driven system is correctly adjusted and lubricated sparingly with light-weight oil it will be easy to manipulate and have the feel of a good condition R-390A gearbox. Since the two tuning ranges cover so much spectrum a clutch-coupled, motor-drive tuning system is provided. A separate motor-drive band switching system is also provided to select the proper band (one of seven) to allow seamless bandswitching as the receiver is tuned throughout it ranges.

The Veeder-Root counter is somewhat different than that used in the R-390 and provides two sets of digits, one for 15kc to 500kc (lower set) and the other for 500kc to 1500kc (upper set.) The resolution of the digits (tuned f) is to the tenth of a kilocycle (which are the red background digit wheels.) Neither a calibration oscillator or an antenna trimmer are provided (or needed.)

Most of the controls are the same as those found on the R-390. The BFO controls, the Noise Limiter, the Local Gain, Line Gain, Line meter range switch, RF Gain, AGC switch, Break-in switch, Audio Response switch and Function switch. The controls that are unique to the R-389 are Motor Drive, IF Bandwidth (five ranges instead of six,) RF bandwidth KC indicator and the single tuning knob. The two meters perform the same functions as the R-390 meters, that is, Carrier Level and Line Level.

More Details - Physically, the R-389 is the same dimensions as the R-390 and will fit into the CY-917 or CY-979 table cabinets. If installed into a table cabinet, the top and bottom covers should be removed. The receiver weighs 82 pounds but, for easier moving (e.g., up or down stairs,) the power supply and AF module can easily be removed and then the receiver weighs around 65 pounds.

Two antenna connectors are available. Balanced input for 125 ohms input impedance from dipoles or other balanced antennae. Balanced is connected to the primary winding of each antenna coil. Unbalanced input is for random length wire antennae. This input is capacitively-coupled through a .01uf capacitor to the RF amplifier coils. The Unbalanced input impedance is not specified but is probably fairly high assuming that end-fed wires were probably the design target Z. The Balanced input utilizes a "Twin-ax" two-pin coaxial connector and the Unbalanced input utilizes a "C-type" coaxial connector. As mentioned, no antenna trimmer is provided so the antenna impedance should be somewhat matched to the particular antenna input used.

Both audio outputs, Local Audio and Line Audio, are 600 Z ohm outputs and can provide about 500mW on Local and about 10mW on Line. The phone jack doesn't disconnect the audio output (LOCAL) from its respective load. There is a series resistor and a load resistor to the PHONES jack to keep the audio level (5mW) from over-driving the headset if the proper 600 Z phones are used.   >>>

photo right
: Top of the R-389 showing the RF module and IF module mounted in the receiver. The RF module has the slug racks located under the cover. The two tubes showing thru the opening are the two RF amplifiers. The Crystal Oscillator and first mixer is the to the left and the second mixer is to the right. The IF module is to the left side of the main frame.

>>>  The AC power connector is a four-pin military connector that is keyed and held in place with a central screw that has a fold-down, wing-type handle. There are at least two different types that fit,...sort of. The original (CX-1358/U cable + connector PN) connector has a small round cylinder-shaped housing with a cable exit tube on the side. This type will fit in almost any orientation and can be used if the receiver is installed into a table cabinet. There is also a large square housing with the triangular top type that will only fit in one orientation that won't interfere with the terminal strip or the fuse housing. With the larger connector installed the receiver must have spacers to elevate the bottom enough for the connector body (if the receiver is setting on a table) to clear the table. Also, with this larger connector, the receiver won't fit into the table cabinets.

Unlike most other LF and VLF receivers, the R-389 doesn't have any fixed-circuit audio restrictions within the audio module other than the switch-selected Broad-Medium-Narrow. Selecting Broad results in a fairly wide audio bandwidth. Medium is shaped for voice with noisy conditions and Narrow is a bandpass filter at 800hz for CW. The IF bandwidth can be restricted down to 100hz. Both 100hz and 1000hz IF bandwidths use a crystal filter that's onboard the IF module. The 2kc, 4kc and 8kc IF bandwidths are determined by the IF transformers and Q-resistor set-up. For static bursts and other types of atmospheric noise, the dual positive-negative noise limiter is available. When tuning in the AM BC range, the receiver's bandwidth can be increased to 8kc and BROAD and, with no other specific audio restrictions, the resulting audio isn't too bad. However, the audio is more-or-less communications-grade audio so don't expect high fidelity because it isn't. Most listening on LW will usually be using a headset. Most listening on the AM-BC band will be on loudspeaker.

The R-389 is a "top notch" MW, LF and VLF receiver but using it today can result in user frustration due the very high noise levels that plague LF enthusiasts in many locations. The R-389 does cope with significant noise levels very well. It can do a good job with a wire antenna (probably what it was designed for anyway) especially if the user is located in a RFI-quiet area. Using a loop antenna may help in extremely noisy areas. Of course, like any LW receiver, best results will be experienced when listening "at night" during the "LW Season" (Oct thru Mar.)

photo right
: Bottom of the R-389 showing the Power Supply module on top, the VFO in the center and the Audio and Electronic Voltage Regulator module on the bottom. Motor drive system is directly behind the front panel. The long rectifier (green with fins) is part of the motor-drive tuning power supply. The long bent metal arm directly behind the tuning knob is the motor-drive clutch actuation arm that is cam-driven from the MOTOR TUNE control. The three coaxial cables behind the VFO are from the Antenna Relay box and are routed to the RF Module.

R-389 Restoration Log (Started March 11, 2018)

This probably isn't really a "restoration" but more of a full and complete "servicing" of the R-389. Includes the removal of any "non-military" modifications in order to return the circuit to the original design. Before starting it's worth noting that the receiver does function - not to spec, but it does receive some signals. This indicates that most circuits are working but probably not aligned where needed. The R-389 is a very mechanical type of receiver and this servicing will probably include not only electronic alignments but also mechanical alignments.

March 11, 2018 - Disassembled receiver by pulling all modules. Power Supply, Audio-Regulator and IF module are easy. RF module requires dropping front panel. Like the R-390A, the gearbox is integral to the RF module. Only the frequency that the receiver (RF module) is tuned to has to be remembered when doing the reinstallation because the VFO (PTO) remains in the main frame.

March 12, 2018
- Finished dismounting the RF module. Inspection of the line shaft gears showed that some type of black grease was used. It's probably Molybdenum-grease. Excessive amounts of "multi-purpose" grease were used in the gearbox. Like the R-390A gearbox, the R-389 gearbox really doesn't need any grease and copious amounts of grease will just trap dirt and then "harden" over time. The manual states that "no lubrication is better than too much lubrication." A light coat of 10W machine oil is all that's necessary. After all, you wouldn't grease a clock's gear work,...right?

March 13, 2018
- Started removal of the excessive grease. I used WD-40 as a solvent to remove and clean the areas on and around the line shafts of the moly-grease used. This required several "cleanings" to remove all residue. Started removing the excessive multi-purpose grease in the gearbox. Anything that rotated was "greased."

March 14, 2018
- Grease, grease and more grease. Some of the grease in the gearbox is as hard as candle-wax. I'm having to scrape it off in some places. I'm using WD-40 applied with a small paint brush but this doesn't hardly touch the hardened grease. I switched over to a small wire brush and WD-40 which removes the hard grease much better.

March 15, 2018
- Used WD-40 to "flush" the gearbox and that got it very clean with all of the hard grease gone. Cleaned all of the threaded rods that comprise the slug rack lifters. The manual Frequency Change still seemed "heavy." I readjusted the motor-drive clutch and discovered it was adjusted to "full engagement." This had the motor-drive clutch turning with the manual tuning. Once the clutch was adjusted to "slip" when manual tuning, the "heavy" tuning was gone and the gearbox "feel" was very much like a clean R-390A gearbox. Also, the slip-clutch in the tuning knob had been adjusted to "full engagement" because of the heavy tuning. The slip-clutch was adjusted to be engaged with manual tuning but to "slip" if any binding or other drag occurred in the entire tuning mechanism. The problem was caused by all of the grease creating so much drag in the gearwork, the motor-drive clutch had to be in full-engagement to get the motor to turn the gears. The slip-clutch in the knob needed to be in full-engagement to turn both the drive clutch and all of the grease.

photo above: Under the RF module after cleaning off all of the grease. Note the two line shafts that drive the gears that turn the threaded shafts that raise and lower the nine slug racks. The motor-drive bandswitch is in the center of the chassis with the gear drive at the very rear of the module. The motor for the motor-drive tuning is in the lower right of the photo. Note the date on the motor - Sep 10 53.
March 17, 2018 - Checked Antenna Relay Box connectors because when operating the receiver, Balanced Antenna didn't seem to work. Found connector J110 center pin damaged on Antenna Relay box. Also, found mating connector, P110 also had center pin bent.

March 18, 2018 - Dismounted Antenna Relay Box and removed bottom plate. I could see that the Balanced Input wiring had been changed from original. The mod has the Bal. Ant. connector wired to go to the output BNC connectors IF the receiver is turned off. When the receiver is turned on, then the Bal. Ant. input is connected to chassis ground. The reason for this mod seems to be prevention of using the Bal. Ant. input. Check April 4th for correction.

March 19, 2018 - Mod to B+ fuse and HV winding CT found. This mod removed the wires from the B+ fuse holder and soldered them together to eliminate the fuse in that circuit. Then the power transformer CT (pin  6) was disconnected from chassis ground in the power supply module and a wire routed from the CT to pin 15 (unused in ps) of J-118. This pin 15 P-118 connection was originally to the DC 20A fuse but was now routed to the B+ fuse holder and then to chassis-ground (on the Local Audio ground terminal.) This mod may have been installed because of the power supply module conversion to solid state rectifiers. It's likely that the "instant on" HV to the electronic regulator circuit tended to blow the 3/8 Amp B+ fuse. With the mod, fuse blowing would be at the power transformer HV winding current draw rather than at the output of the HV rectifiers to the input to the voltage regulator circuit. The mod also changed the fuse to 3/4 Amp.

March 20 - April 3, 2018 - I had to set aside the R-389 project temporarily. A Collins 32V-3 was acquired that needed testing, servicing and clean-up. I'll get back to the R-389 when the V-3 is completed (a few days, hopefully.)

April 4, 2018 - Well, two weeks (two other projects in addition to the V-3) and back to the R-389. De-mod'd the Power Supply by removing wire CT to pin 15 J-118. Reinstalled the correct bare 14 gauge, "tinned-copper" (TC) wire from chassis to both CT pins on power transformer as original. This completed the Power Supply.

Correction - Checked the Antenna Relay Box again and found that it is correct and original. The relay contacts are actually for grounding the antenna inputs when Break-In is actuated.

photo above: The gearbox after cleaning out all of the dried grease. The tuning knob has a built-in slip-clutch that's adjusted by the four recessed screws in the flutes of the knob (two screws are visible in the photo.) Behind the knob is the motor-drive clutch that is engaged when the motor drive switch is turned. This pushes down the lever which pivots against the adjustable standoff to the right and presses the clutch in which then drives the gears for motor tuning. Manual tuning is accomplished with the tuning knob and runs the gear train if the motor drive clutch is disengaged (that is, receiver not in "motor drive.") The tuning knob does "spin" while motor drive tuning.
April 5, 2018 - The B+ fuse mod had actually broken the side terminal off of the DC 20A fuse holder. I had to remove the TC (tinned-copper) wire and the large gauge stranded wire from the to rear terminal in order to remove the broken fuse holder. I located a duplicate of original, good condition, original fuse holder to install.

April 6, 2018 - Removed all wires from non-original connections. Cleaned, straightened and re-tinned all lead ends. Installed DC 20A fuse holder and connected and soldered original wires. Re-wired B+ fuse to now have the original connection to the HV rectifier output. Cleaned all "mod writing" off of the back panel using WD-40 and "Goof-Off." This completed mod removal on the Main Frame.

April 8, 2018 - Performed the check on the mechanical alignment for the RF module. This check involves setting the lower frequency readout to specific frequencies and then checking the height that specific slug racks have been raised. All checks are verifying the each of the nine slug racks are at their maximum lifted height and also at specified heights from the top of the RF coil shields at the specified frequency readout. There are silk-screened frequencies and lines that measure the specified height on the back of the rear panel of the RF module. The test starts at 14.8kc and goes through eight other settings ending with 565.0kc. Though the written procedure is in the manual, it's easier to just use the silk-screened information on the back of the RF module. All nine slug racks were at the proper height at the specified frequency. This check only assures that the slug racks are traveling correctly. The electronic alignment will assure that the slugs themselves are at the correct position for accurate tracking.
April 10 - 14, 2018 - Another distraction. This time it was checking out the W6MIT-built "1625 Rig" - a homebrew transmitter. Acquired on April 10 and had it "on the air" on the 14th.

April 15, 2018 - Back to the R-389. I double-checked some of the RF module mechanical alignments just to verify that everything was correct. Cleaned up some residual grease and splatter that I'd missed earlier. Cleaned the Main Frame bedplate. Cleaned the Veeder-Root counter and repainted the decimal point. Reinstalled the RF module into the Main Frame. This has to be carefully done because there are four cables that have to be routed through holes in the bedplate as the module is lowered into place. The position of the module has to be slightly moved so that the three bedplate captive screws thread in along with the two side screws and the one rear screw. When all six screws have been partially threaded into their pem-nut receptacles then all of the screws can be tightened. Don't over-tighten. Just snug is enough.

Mounted the front panel. The only unusual item to remember to install is the spring-loaded shaft that couples the Frequency Range switch to the mechanism that operates the dial mask. There is a steel brace that screws between the bottom of the RF module at the gearbox to the Main Frame that has to be installed. There are eight 10-32 FH screws that mount the front panel to the Main Frame that have to be installed. The motor drive power cable has to be plugged in. The two harness connectors have to be plugged into the RF module. The three antenna coax cables that come from the RF module and are routed through the Main Frame have to be plugged into the Antenna Relay Box. The remaining coaxial cable connects to the VFO.

I noticed that several of the knobs were the incorrect size for where they were installed based on the panel nomenclature size. I referenced the manual artwork and the manual front panel drawing to install the correct size knobs in their proper locations. Went to my R-390A spare knobs box to find nice condition replacements as needed.   

April 16, 2018 - Touched-up the chips on the knobs that had problems. Not all had chips. About five needed touch-up. I used black nitrocellulose lacquer applied with a small brush.

I found a correct style, good condition Line Level meter on eBay. This was cleaned up and installed. Apparently, when the original R-389 meters were removed the meters were "chopped" out with a cold chisel. On both meters, three of the mounting screw holes had paint scraped off however one hole on each meter mounting was severely "gouged" with a huge aluminum burr that prevented the meter from setting flush against the panel. I used masking tape to protect the panel and then used a file to remove the gouge's deformed metal to allow the meters to mount correctly. Once the Line Level meter was installed, the wires were soldered to the terminals. NOTE: It's odd that the original meters would have been removed for radiation since the original R-389 meters didn't have radium coated needles or scales.

More grease! This time on the VFO front gear driven switch. Also the oldham coupler was all greased up. The only reason for the grease on the oldham coupler is to hold it in place while installing the VFO. Only a very small dab is necessary on one side only. Once the greasy mess was cleaned up, the VFO was installed. I had set the frequency to 780kc (no particular reason but it's easy to remember - KOH's freq) so, since the VFO position wasn't moved and the RF module was set to 780kc, then the oldham coupler was in the correct position to allow the VFO to mount easily. The VFO is mounted with five captive screws. (I later had to actually synchronize the VFO for the correct output frequency of 470kc at 15.0kc.)

Installed the Audio Module and installed the Power Supply Module.

There was a brass blade screw used on the front panel to mount one of the resistor boards. Replaced this screw with the correct stainless steel flat head Philips screw.

Cleaned IF module as it seemed to have a light coating of oily dirt on it. Installed IF module and connected the three coaxial cables and the power input plug.

The R-389 was now ready for power-up, testing and electronic alignment.

April 17, 2018 - The Carrier Level meter wasn't the correct style. I've been unable to find a suitable one on eBay or from other sources. I decided to harvest a Carrier Level meter from a junk R-392. These meters look similar to the meter used in the R-389 but the scale is slightly different. Original meter FS was 100db and, although the R-392 meters have 100db as the highest number shown, the scale goes one more graduation beyond (or around 120db FS.) Also, the R-392 meter has "DB CARRIER LEVEL" on the meter scale where the R-390 meter just has "DB" on the scale. Additionally, the meter case is actually slightly larger. When mounted, the meter is in contact with the beveled spacer on the grab handle. It's a tight fit but it will fit. One other problem is the meter FS current is slightly different resulting in a fairly "stingy" meter reading. So, I spent a couple of hours harvesting the R-392 meter and installing it into the R-389. It was a waste of time because the very next day an original R-390 Carrier Level meter came up on eBay. When it arrives, I'll replace the R-392 meter.

photo left
: The RF module with the cover removed. The two tubes between the slug racks are the RF amplifiers. Note the motor-driven bandswitch behind the tubes. The two left-most slug racks tune the VFO and Mixer Output Stages and Output Coupler. The remaining seven slug racks tune the bands 15kc-27kc, 27kc-56kc, 56kc-128kc, 128kc-255kc, 255kc-500kc, 500kc-855kc, 855kc-1500kc. Below the slug racks are the 34 RF transformers. Four for each band (28,) four for the output coupler and two for the VFO-Mixer output. Note the threaded rods that lift the various slug racks and the associated return springs (visible in the foreground openings.) The threaded rods are gear-driven by the two line shafts that are below the RF module chassis.

Powered up the R-389  - Everything is working. Motor drive is now fast and not bogging-down at all. Manual tuning is very light and feels like a clean R-390A gear box. Seems like there's a lot more audio now. Operated the receiver for about an hour. Tuned AM-BC KOH, then went to 60kc WWVB and 24.8kc NLK. Alignment is next after several more hours of "burn in."

April 18, 2018 - Ran the R-389 for a couple of hours. I'm sure this receiver was rarely operated by its former owner. It was in a small storage room located under the house when I picked it up. I believe that getting some "hours" on it will help reveal any latent problems and should result in a better alignment.

April 19, 2018 - Aligned the IF module. 455kc IF transformers slightly off. Gained about 1 vdc on Diode Load after 455kc IF transformer adjustment. Crystal Filter off quite a bit, especially the core adjust that equalizes the output on the .1kc and 1kc positions. AGC adjustment off quite a bit. About one full turn of the adjustment to attain maximum AGC voltage. Ended up with increase of +10db on CL meter.  >>>

>>> Performed the alignment on the VFO output stage, the Injection Mixer stage and the Output Coupler stage. This requires a RF probe and VTVM to monitor the test jack level and adjust for maximum output. The RF signal generator is not required because the circuit's crystal oscillator is used as the signal source. Alignment was fairly close but still some improvement was gained. Another note,...this was a good test for the motor drive system because alignment points are at the extremes of the tuning range. Motor drive worked great with no hesitation or bogging-down - just fast and easy to go from 15kc to 500kc or from 500kc to 1500kc in about 30 seconds or less.

April 20, 2018 - Aligned First Mixer Output Transformer, Second Mixer Output Transformer and the 10,455kc Crystal Oscillator. This entire section of the receiver was out of alignment. The Crystal Oscillator requires using a VTVM to read maximum RF voltage. One adjustment is accessed from under the receiver and the RF Module brace has to be removed (just two screws.) This adjustment was quite a bit out from peak. The secondary (top side adjustment) was severely out from peak. These adjustments resulted in another +10db increase in signal level on the CL meter. The next step is to align all of the slugs and trimmers for the seven bands that cover from 15kc up to 1500kc.

April 21, 2018 - The original style Carrier Level meter arrived today in excellent condition. Didn't need any cleaning as it looked almost new. Installed CL meter using correct type of hardware. Adjusted the CL meter pot for showing +5db with no antenna (just slightly above zero.) Tuned in local AM BC station and the CL meter went up to +70db. Tuned off of station and noise level showed about +20db. Nice improvement. Still have to align the slugs and trimmers on the seven bands. Since the signal generator has to be able to produce a sine wave down to 15kc, I'm going to have to use my HP Function Generator for signal inputs below about 50kc. I'll probably switch over to the HP 606B at 50kc or so. Most RF signal generators only operate down to about 50kc, some only go down to 100kc or so. For VLF applications it becomes necessary to use a Function Generator and produce sine wave outputs as low of a frequency as required. Most Function Generators will produce wave forms as low as 1hz or lower. They are ideal for alignments and checking signal response on the VLF range and the lower LF regions. (I actually found that this HP Function Generator was very unstable at 15kc up to 50kc. Both frequency and amplitude varied so much and so quickly it was difficult to align the receiver.) April 22, 2018 - Performed the RF tracking alignment. There are two tuning ranges but there are five bands in the 15kc to 500kc range and two bands in the 500kc to 1500kc range. Each band has four slugs and four trimmers the need to be adjusted. I didn't need a spline-wrench for adjusting the slugs as with a R-390A. Just a blade screw driver, like the R-390. I used a function generator from 15kc up to 50kc. From 50kc and up, I used the HP 606B RF generator. (Read update at the bottom of this section for problem encountered due to using the HP Function Generator.) After the RF tracking alignment, I gained another +5db on the Carrier Level meter when tuned to a local AM BC station. Off frequency CL measures +15db and on frequency CL measures +75db. Checked NLK, the USN MSK station from Jim Creek, Washington on 24.8kc. This station measured about +20db on the CL meter. NPM (USN MSK from Hawaii on 21.4kc) also measured about +20db. Listening was all on loudspeaker.

April 23, 2018 - Adjusted R-260. This adjusts the balance on the First Mixer with one signal from the 2nd RF amplifier and the other signal from the Mixer Driver (VFO plus other stages.) This adjustment was off causing about a 2 volt increase over the minimum setting. Reduces Mixer noise.

Performance - On Wire Antenna - Late-April isn't the best time for testing on Long Wave, especially using a wire antenna, but, the testing was done at 10PM in the evening to help with signal levels and with the noise. I used the 135' CF Inv Vee with 96' of ladder line with the lines tied together. This wire antenna usually provides adequate signals although the noise level is pretty high. I tuned from about 410kc down to 320kc. I had the Audio Gain at about 5 or 6 and the RF Gain at about 7 or 8. MGC was used and the BFO was on. The Unbalanced Antenna input was used. I heard MOG 404kc very loud, it's in Montegue, CA and runs about 50 watts. Also, very loud was BO 359kc in Boise, ID. Many NDBs were heard from Oregon, like MF, OT and MEF. Canadian NDBs copied were XX, NY and DC. All pretty easy ones. Conditions were okay for late-April but the noise level was very high. The R-389 seems to be operating like a typical, high performance Long Wave receiver in that many stations can be tuned in and it is capable of decent copy even though the antenna and the conditions weren't ideal.  - April 23, 2018 Antenna Testing - When first acquired this R-389 didn't receive signals if the Balanced Antenna input was used. I wanted to test that the problem was repaired (the bent pins on the BNC connector P110 and receptacle P110.) Connected a Twin-ax to UHF coax adapter to the Balanced Antenna input and hooked up the wire antenna. Local BC station KOH was showing +75db on Unbalanced and +72db on the Balanced input so the problem was corrected.

The next test was to check the remotely tuned loop antenna operating with the R-389. When first acquired this R-389 didn't receive any signals using the loop antenna. I now connected the loop to the Balanced Antenna input and tuned to 314kc which is the frequency of a nearby DGPS node (read - "very strong signal.") The DGPS signal was received and could be tuned with the variable bias control on the loop. I noticed a significant improvement when the shield of the remote tuner was grounded to the receiver chassis. I also used the HP 606B RF signal generator (connected to a small antenna) as a signal source that could be tuned. This verified that the remote loop could be "peaked" or "tuned" to various received frequencies and that the Q of the antenna was fairly sharp. The higher Q with a sharp peak will give good signal strength with low noise since the antenna is only responding to a very narrow tuned frequency.

Next tests will be with the remotely tuned loop on the Balanced Input and listening at night.  - April 24, 2018

Performance on Loop Antenna - I tested the remotely tuned loop antenna at 10PM in the evening so it would be fairly close to the conditions that were present when I tested the wire antenna. The loop was attached to the Balanced Antenna Input. I first tuned to 314kc for the local DGPS signal. It was strong and could be "peaked" with the loop's remote tuner. I proceeded to tune from 325kc up to 405kc. Only the very strong NDBs could be heard. BO 359kc and MOG 404kc. I tried the Unbalanced input with even less response. I switched back to the wire antenna but with it connected to the Balanced input. Signals were much stronger and all of the usual NDBs were tuned in. Signals from Oregon, Montana and Idaho were copied. Also WL 375kc in Williams Lake, BC, Canada.

Further testing will be required to determine why the Loop Antenna performance is not as expected. I did modify the Loop to perform best with the Hammarlund SP-600VLF. I may have to do further modifications to the Loop to attain best performance with the R-389.

Another possible explanation is the time of year. Late-April isn't the best time for MW or LF signals. Most of the time, I quit listening to this part of the spectrum by late-February because of much higher noise levels and low signal levels, even at night. -  April 24, 2018

Signal Generator Test - A quick test used the HP 606B directly connected to the Balanced Antenna input. I used a fully shielded coaxial cable to input the signal. I set the HP 606B to the 0.1v scale and set the meter to read 1.0. This signal read 100db+ on the CL meter at 200kc. I used the attenuator to lower the signal level in steps. At 1uv input the CL meter was just at the internal noise level and the signal was easily audible on loudspeaker. I repeated the test at 300kc and at 700kc with the same results. This isn't a true sensitivity test, it's just to see that the receiver does respond to very low level signals.

So, what I can say right now is that the R-389 seems to be performing well. It does better on a wire antenna on LW. On the AM-BC band signals are very strong and push the CL meter to nearly +80db. The USN MSK VLF stations also will move the CL meter to about +30db. A comparison test with the SP-600VLF might be an interesting experiment.  -  April 25, 2018

Comparison Test - I tuned in a few signals using the SP-600VLF using the wire antenna (during mid-day.) I could just barely hear MOG 404kc. DGPS 314kc was strong. WWVB 60kc strong and NLK 24.8kc and NPM 21.4kc were strong. I tuned in the same signals with the same antenna using the R-389. The results were nearly identical. The exception was I could easily hear the carrier of MOG but I could only hear the MCW signal a few times. My conclusion is that the R-389 performs just about like the SP-600VLF. See September Performance Update below.

Minor Problem Corrected - This R-389 had this unusual problem that when first powered up the received frequency was about 20kc low. The former owner told me at the time of purchase that the receiver would have to "warm up" and after several minutes it would jump to the correct frequency. I experienced exactly what he described in that after the receiver "warmed up" for twenty minutes, the tuned frequency would jump up 20kc and then everything was ready to use. This didn't seem normal but it wasn't too much of an issue since one usually allows a receiver to "warm up" anyway and it always took the same amount of time for the frequency jump to occur.

After all of the repairs and the alignment, I used the receiver for awhile. When installing a new Twin-ax to BNC adapter on the Balanced Antenna input, I happened to notice that the OVEN was turned ON. I checked the manual and read that the oven was only on the VFO and was designed to raise its internal temperature up to 167F - Wow! Anyway, I started testing the R-389 with the VFO oven off. The frequency "jump" never happened after I turned the OVEN off. I left the receiver turned on for hours and always the tuned frequency remained 20kc low.  >>>

>>>  In thinking about this problem, I knew that I hadn't synchronized the VFO as I always do on any R-390A that I align. On the R-389, at 15kc, the VFO output should be 470kc - exactly. I used a tube extension to access pin 5 of V702, the VFO buffer output tube. I used a digital frequency counter to measure the frequency exactly. It was 452kc at 15kc on the Frequency Dial. I had checked the mechanical limit-stops prior to this and those were okay. I assumed that in the past during an alignment someone skewed the VFO to correct the frequency readout with the VFO oven ON. I loosened the clamp on the VFO coupler behind the gear-driven mechanical limit-stops. This allowed me to just change the VFO only. I set the VFO for 470kc output with the frequency set to 15kc and tightened the clamp. I then checked the DGPS node at 314kc and it was at 313kc (BFO on) and I also checked local AM BC KOH 780kc and it was at 780kc with the 2kc bandwidth. A "touch-up" on the alignment was going to be required. Actually, the adjustments below about 150kc were pretty far out. The higher the frequency, the less the alignment was affected. More details in the next section below.

Is this "Oven Induced Frequency Change" a component that fails under heat? Or, is it a component the suddenly "gets better" with heat? With the instant nature of the change, I'd think the component fails with excessive heat. I'm just going to leave the VFO oven turned OFF and use the receiver. In hours of operation the VFO never gets as hot as when its oven is ON (167F - that's hot!)   May 10, 2018

A Different RF Signal Generator - I wasn't very confident that the HP Function Generator provided a very stable signal for alignment below 50kc. It seemed to be very erratic in both amplitude and frequency. The HP 606-B would only tune down to 50kc. I happened to look at my General Radio Type 1001-A RF Signal Generator and noticed that it would tune down to 5kc. It's a top-notch generator dating from about two decades before the HP 606B. I had tested and serviced it a few years ago so it still was operating quite well. I decided to use the GR generator for the next alignment which was after the VFO had been synchronized as mentioned in the section above. The signal from the GR 1001-A was super stable both in amplitude and frequency. I found that the alignment I had done using the Function Generator was off by quite a lot. It's important to remember that adjusting the slugs doesn't affect the accuracy of the frequency readout. That's a function of the VFO and the 10.445mc Crystal Oscillator. You have to set the receiver frequency as specified and then "rock" the signal generator frequency and set it to the "peak" output as measured at the Diode Load. Then adjust the slugs for that band at that frequency. Do the same for adjusting the trimmers for the top end of the same band. Most of the errors in adjustment were below 150kc. Above 150kc there was very little error. The end result is much more gain in signals below 150kc and especially below 50kc.     May 13, 2018 PERFORMANCE UPDATE:  September 24, 2018 - Finally the Autumnal Equinox has arrived and conditions on LW, especially in the early mornings are improving dramatically. All summer-long, I'd perform tests on the R-389 trying various LW signals using combinations of antennae from loops to wires. Barely any signals were audible. Once in a while, the carrier of MOG 402kc in Montegue, California could be heard but usually the MCW was not audible. At night, the static crashes and other atmospherics seemed to mask all of the LW signals except for the DGPS nodes which were about the only thing that assured me the R-389 was at least receiving some types of LW signals.

With the Autumnal Equinox approaching, I began by listening in the early evening on 9/21/18, which was the day before the Equinox. Only two NDBs were heard, MOG and ULS (392kc, Ulysses, KS) and the noise was still pretty severe. I decided that in the next couple of days I would have to try early morning to see if the noise was down and maybe the signals would be up.

At 0530 on 9/24/18 I started listening using the 100'x135' "T" antenna. Right off, I tuned in ZZP 248kc from Queen Charlotte Islands, BC. Multiple NBDs were heard on many frequencies. I tuned around 390kc and heard what sounded like a voice transmission. I widened the bandwidth to 4kc (from 2kc) and at 394kc I easily copied voice weather being transmitted. With BFO turned off, I could hear in the background RWO being sent in MCW. This was the NDB on Kodiak Island that transmits TWEB or Voice Weather. In about 30 minutes of listening, I had tuned in about 30 NDBs, three of which were newly heard NDBs, ZZP 248kc, RWO 394kc and POY 344kc (#328, #329 and #330, respectively.)

I guess this illustrates that besides a quiet location, a large antenna and a superb receiver, good receiving conditions are absolutely necessary for successful LW DX copy and that my concerns about the R-389's abilities to cope with the modern LW reception issues were unfounded. As conditions continue to improve, I'm looking forward to the "peak LW reception" which will be from mid-November thru mid-January.   

R-389 UPDATE: Oct. 1, 2018 - Tuned in LLD 353kc in Hawaii at 0545 this morning using 100'x135' "T" wire antenna. Also, tuned in JJY on 40kc, pulse-encoded time signal from Japan at 0615.

R-389 UPDATE: Oct 18, 2018 - LW conditions are just getting better and better. 50 stations tuned in about 45 minutes starting about 05:30. DB 341kc Burwash Landing, Yukon, CAN, FS 375kc Ft.Simpson, NWT, CAN along with ZF 356kc Yellowknife, NWT and MM 388kc Ft. McMurray, AB were some of the Canadian NDBs. LLD 353kc Lenai City, HI is a regular every morning. I'm finding that the R-389 maintains excellent sensitivity even with the Bandwidth set to 100 cycles (.1kc.) Using the 100'x135' "T" wire antenna.

R-389 UPDATE: Nov 13, 2018 - Listening evenings now that we're back on Standard Time. YY 340kc Mont Joli, QC, Canada, YXL 346kc Sioux Lookout, ON, Canada, IN 353kc International Falls, MN were some of the NDBs heard around 19:30 PST. Also heard MA 326kc Midland, TX which isn't that far away but it's on the same frequency as Canadian powerhouse DC 326kc Princeton, BC, Canada. Also, I'm noticing that I can easily tune in NDB stations between the DGPS nodes located from 285kc up to 325kc in the West. All listening was with the bandwidth set to 100 cycles. Still using the 100'x135' "T" wire antenna as the noise isn't too bad and signals seem very strong using the wire antenna.



Hammarlund Manufacturing Company, Inc.




 MW, LF & VLF Superheterodyne Receiver

10kc  to  540kc


SN: 20101    from 1955


When the first paragraph of the SP-600VLF-31 manual states that the receiver is unique because the tuning "extends to audio frequency 10kc" one wonders whether the writer of the manual understood the difference between 10kc of varying air pressure (sound-audio) and 10kc of radio frequency oscillation (a varying electromagnetic field.) Of course, the writer may have just been thinking of an RMS voltage varying at 10kc. The SP-600VLF is not just an HF SP-600 with LF coils in the turret. It's a very different receiver that was designed specifically for longwave reception. The SP-600VLF-31 was first offered in 1954. It was the first VLF version of the SP-600 series with a later SP-600VLF-38 for 25 to 60~ AC operation being the only other version produced. The receiver shown here is from 1955 (ink-stamped June 27, 1955 on backside of the front panel.) Hammarlund also produced several SP-600VLF receivers  for the Dero Company and these receviers will have the Dero name on the front panel.

The 1950s was a time when the radio frequency spectrum below 500kc was brimming with signals that included many voice transmissions and lots of true CW transmissions. Signals that could be tuned included airport beacons (many with voice weather reports,) maritime weather and navigation signals, ship to ship traffic, ship to shore traffic, long wave AM broadcasting from foreign lands to name just a few. Nothing like today's almost entirely data-driven transmissions that defy decoding, unidentifiable signals of all varieties and the rapidly diminishing and displaced airport beacons (Non-Direction Beacons or NDBs.) In the 1950s, the SP-600VLF would have been used in the laboratory, in commercial coastal stations or perhaps onboard ship. It was an expensive receiver that probably wouldn't have interested the average radio amateur or average radio listener. It was mainly for laboratory, commercial or military users.

Comparison to the HF SP-600s - One notices the although the receiver is obviously a "600" it has several minor physical differences. One first sees that the chassis and most of the sheet metal is gold iridite finish. Also apparent are the quite different side panels used on the VLF (similar to R-390A panels.) Another difference is the "X" option that on the HF 600 has six positions and uses HC-6 crystals but on the VLF has only four positions and uses FT-243 crystals. The Carrier Level meter is also only a single scale, bakelite case unit reading "db over 50uV" while the HF 600 meter is usually a metal-cased, dual scale unit. With the dual scale meter, a switch for RF-AF is on the HF 600 that is not necessary on the VLF. A "warning" tag is mounted between the tuning dial and the logging dial  There are two additional IF cans that are smaller than the standard IF cans that are for the AVC and for the IF output. The "X" option oscillator uses a different tube. Antenna input is not on the RF platform but is terminals on a rear bracket.
photo above: Note that most of the coupling and decoupling capacitors are ceramic disks on this 1955-built SP-600VLF.
VLF Circuit - The SP-600VLF is not just an HF SP-600 with LF coils in the turret. It's a very different receiver. First, it's not a double conversion receiver (like the HF version) but it is double preselection in that two RF amplifiers are used on all bands. The frequency coverage is from 540kc down to 10kc in six bands. 21 tubes are used in the circuit (20 tubes are used in the HF version.) The IF is 705kc and a dual crystal filter is used for selectivity. One crystal filter is ahead of the first IF amplifier and the other crystal filter is ahead of the second IF amplifier. Five different IF bandwidths are available and all positions utilize the crystal filter (the HF version uses three of the six positions for the crystal filter.) There is a 1160kc crystal oscillator circuit in the receiver but this is to heterodyne with the 705kc IF to provide a fixed 455kc IF OUTPUT to drive RTTY devices or other types of equipment that require a 455kc input signal derived from the last IF amplifier stage (full selectivity.) The audio output uses a 600Z ohm transformer that's very similar to the HF version. AVC is provided as is a BFO and there is a Noise Limiter circuit. As expected for the vintage, the 600VLF uses a standard envelope detector circuit so the RF Gain has to be reduced for proper signal to BFO injection ratio (also the AVC should be off.) The "X" function provides for only four crystal channels using FT-243 type crystals. This "X" function provides a crystal controlled oscillator in place of the LO for increased stability. With two RF amplifers and four IF amplifiers provided the SP-600VLF has a lot of sensitivity and a lot of gain - but does that really help in today's noisy LF region of the spectrum?
VLF Performance - Noise versus gain - that's the problem. Certainly the number of times that the SP-600VLF receiver will be tuned to a voice modulated carrier signal, with AVC on and the BFO off, will be very limited. AM BC at 540kc and public information BC at 530kc will be about the only AM voice signals easily received. The only other voice modulated carrier signals will be from LW BC stations. Of the LW BC stations that can be heard in the western USA only Radio Rossii was an easy station to receive. Other LW BC were extremely weak so the tuning is done with the BFO on and tune to zero beat. This is called an "exalted carrier" type of reception of AM and it sometimes helps with weak signals. Unfortunately, all I could ever hear was the carrier and the modulation wasn't detectable. 

It's worth noting that, in 2014, I haven't been able to reliably receive Radio Rossii 279kc from Sakhalin Island due to a digital-data beacon also on 279kc. In late November 2013 I was able to hear Radio Rossii somewhat using the 6' loop antenna but the beacon severely limits intelligibility. Radio Rossii was the only LWBC station that could be received in the west and it now appears to have a case of "chronic QRM." (Radio Rossii LW BC shutdown Jan. 9, 2014)

Although NDBs are MCW signals, all "NDB-chasers" use a BFO (tuned to the exact IF) to help locate the NDB carrier and then tune to zero beat to copy the MCW (this method results in a nice sounding 400~ note.) Best results for NDBs has the AVC off, BFO on and riding the RF Gain control.

Nearly all operation of the SP-600VLF will be with the RF gain throttled back to 5 or 6, Audio gain at about 5 to 7, with the AVC turned off and the BFO on (I've started having the AVC on in an effort to help reduce "pops and crashes" - it helps a little bit is all.) I've found that Selectivity at 1.3kc gives the best signal to noise ratio. The Crystal Filter should be set for narrowest bandwidth (about 8 or 9 on the dial scale.) With high noise it's sometimes better to reduce the Selectivity to the narrowest bandwidth while keeping the Crystal Filter at about 8 or 9. A 600Z ohm headset connected to the 600 Z ohm audio output (not the phone jack) gives the best results for weak signal detection. The Noise Limiter and AVC circuits are not very effective on static bursts or electrical "pops" so keeping the 'phones in front of the ears is necessary during these types of conditions. I'm using a six foot remotely tuned loop antenna. Nearly all of the NDBs tuned in seem to have two or three signals on each frequency. Stations below about 100kc will probably require an outdoor wire antenna for best reception. Stations like JJY (40kc) or WWVB (60kc) can be received with the AVC on and with the BFO off which lets the Carrier Level meter function. In this set-up you can watch the meter respond to the pulse-encoded signal that either station sends out. USN Submarine Fleet comm stations NAA, HOLT, NPM and NLK are very strong MSK Navy VLF stations in the 19kc to 25kc region of the spectrum. MSK stations will require the BFO to be on. No information can be decoded from these stations and their usefulness to LW enthusiasts is that their exact frequency is known along with their location so they provide excellent test signals for the VLF region of the spectrum.

My first serious listening session was using my 80M Inverted Vee antenna with the feed line shorted. I logged two newly-heard NDB stations. Not that they were any great DX, being PND 356kc in Portland, OR and BF 362kc in Seattle, WA, but they were new ones (#259 and #260, respectively.) Super smooth tuning with oversize controls only adds to the pleasure of using the SP-600VLF.

Chronic Dial Slippage - All SP-600 receivers mechanically drive the tuning using the same set up. A brass drive wheel is rotated with the Tuning knob. This wheel in turn drives, by friction, a brass reduction wheel that is spring-loaded against the drive wheel. The reduction wheel is grooved and mates with the Logging dial driving it, by friction, at its perimeter. If contaminates are allowed to accumulate on the friction drive surfaces eventually dial slippage will be the result. Although some SP-600 enthusiasts believe that the "S" spring used for loading the reduction wheel causes the slipping, I've seldom had just the spring be responsible for dial slippage. Almost always, dirt and grease will have collected on the friction surfaces of the brass wheels or on the rim of the Logging dial and this is what is causing the slippage. Thorough cleaning is necessary to correct the problem. Fortunately, all parts are accessible without any disassembly. The brass wheels and be accessed with the receiver on its side and the Logging dial rim can be accessed from the top. Clean all friction surfaces with denatured alcohol. I use several Q-tips to clean the brass wheel surfaces. Repeat the cleaning until the Q-tips don't turn black. On the rim of the Logging dial, I use a small piece of paper towel that is dampened with denatured alcohol. Again, clean until the towels don't turn black. Remove and check the "S" spring. It should be straight or slightly bent out. If it's bent inwards then the spring load will be somewhat reduced. You can expand the "S" spring by just bending it outwards with your fingers. Reinstall the "S" spring. As an added help, lubricate all of the bearings with a drop of 10W machine oil. Also, check that the Dial Lock is completely open and not "dragging" on the Logging dial. Check the SP-600 tuning now. It should not slip and should be "velvet smooth."

UPDATE: Jan. 1, 2018 - The slipping dial is back. Although I haven't pulled the receiver out of the cabinet I can see what I think is the problem. The logging dial rim has a small gouge that I think is causing the slippage since this "dent or gouge" changes the dial friction in the drive wheel groove when the gouge comes around. I also noticed that the logging dial has a significant bend so it isn't really engaging into the drive wheel groove with the same "fit" each revolution of the drive wheel. To repair this will be a receiver out of the cabinet and front panel off since I'll have to dismount the logging dial for straightening and repair of the gouge. I'll do this after the Longwave season is over - probably around March.

UPDATE: May 1, 2018 - Slipping dial issue required pulling the receiver out of the cabinet and then disassembling to the point where the front panel could be removed. The dial lamp assembly over the logging dial has to be removed. Then the three screw mounting plate is removed and the logging dial can be removed. Close inspection revealed that near "45" on the dial rim there was a deformation that had a "lumpy" feel to it. Also, between "50" and "55" was another rough area. I carefully dressed these areas with a fine file. The dial also had a warp that was easy to take out with minor flexing of the dial. Upon reinstalling the dial on the hub, I found that the slipping was still happening in the same areas. I readjusted the "S" spring for a greater load against the drive wheel. No improvement. I thought about how improve the "grip" of the brass against brass surfaces and came up with using rosin. I dissolved some powdered rosin in some denatured alcohol to make a thin (viscosity like water) mixture. I used a small paint brush to apply the rosin mixture into the drive wheel groove. Then I rotated the logging dial to transfer some of the rosin mix to the rim of the dial. I let the mix dry (alcohol evaporates.) That did it. No more slipping - at all! I didn't need much rosin-mix, just a little brushed just into the drive wheel groove worked great. If the rosin somehow disappears from the drive wheel groove in the future, it's very easy to reapply the rosin-mix. Hopefully, the "grip" will last for quite awhile.

Also, during this rework that required removing the front panel, I noticed that the gray rubber boots over the toggle switches had deteriorated to the point where two of them ripped and came apart. Fortunately these rubber boots are still being made by the same manufacturer and using the same part number. I ordered a new set of four gray boots from Grainger via their eBay listings. The price was $4.50 per boot. The boots are for 15/32"-32 toggle switches and are manufactured by APM HEXSEAL (part number is IN1030.) I know these aren't original,...neither are the grab handles nor the fillister-head slotted screws used in each corner for the panel mounting,...but I think that these additions improve the front panel appearance and aren't serious deviations from originality.

photo above: The carrier level meter is unique to the SP-600VLF

photo above: Only four crystal positions are offered in the X option

photo above: Tag between the tuning and logging dials

photo above: The unique, iridite-finished side panels of the 600VLF

Conclusions - Medium Wave and LF Amateur Operation - NDBs are going "off the air" in droves. LW BC stations are almost totally gone. Loran-C is "long-gone." The spectrum below 500kc is rapidly becoming exclusively data transmissions that require special equipment or computer programs to decode. Nowadays, the SP-600VLF might have become a high-quality receiver that could be used to hear just a few interesting signals. Fortunately, now there are some MW and LF amateur bands that can present a real challenge for the SP-600VLF. 

Amateur operation on 472kc to 479kc (630M band) requires UTC approval for ham operations. Regulations allow CW and data with 5 watts EIRP.  As of March 2018, I've been successfully using the SP-600VLF as the receiver in my 630M station. I'm using a six-foot remotely tuned loop antenna for reception. The station is described in detail with photo in the section "Operating Vintage Gear on 630 Meters" further down this webpage.

The SP-600VLF is a "top notch" LW receiver but using it today can be frustrating in some locations due to the very high noise levels that plague many LF enthusiasts. Special antennas are necessary for practically any receiver that tunes below 500kc and the SP-600VLF is no exception. The user's ability to hear LF signals will benefit greatly by employing a noise-reducing antenna system which generally means using a tuned loop of some kind.

SP-600VLF-31 UPDATE: Nov 2014 - Using the Remote Tuned Loop Antenna - I decided to try the six foot remote-tuned loop antenna with the SP-600VLF-31 receiver. The loop suffered a bit during the move down here to Dayton. I had it stored in one the shop garages. I brought the loop out for inspection and found that the wire had come out of the grooves in the combs in several places and there was wire hanging and getting tangled. All that was needed was to straighten out the wire and get it back into the grooves of the combs to get everything looking okay again. During the move I discarded the loop's stand because it was beginning to fall apart. So now I'm without a stand for the antenna but it can set on one of its corners and be propped up against the wall - at least for testing. A new 9vdc battery was installed to get the bias and remote tuning working again.

With the tuned loop upstairs and propped up so it was pointing sort of north-south, I tuned in FCH 342kc and peaked the signal using the remote tuner. What I noticed was the gain peak was not as pronounced as it seemed to be with other receivers. Still, there was a peak, so I figured the loop was working. I waited until dark and then positioned the loop east-west. In tuning from around 325kc up to 400kc several NDBs from the US mid-west were received and several Canadian NDBs from Manitoba and Ontario were also received. The improvement over the "ham antenna" with the feed line shorted was dramatic. The only thing noticed was the "peak tuning" of the loop is very broad and not all that much gain change is noticed. I suspect that there may be an impedance mismatch between the loop and the SP-600VLF-31 that will require a little more tweaking. But, for now, I have a nice improvement in signals and some directivity. - November 15, 2014         Removing one turn on the pick-up loop, which had three turns and is now two turns, has improved the loop performance with the 600VLF. Sharper tuning (higher Q) and seems to have better gain. - November 17, 2014        

NOTE: As of JAN 31, 2015 - 23 "newly heard" NDBs with the SP-600VLF so far with well-over 200 NDBs logged. Also, the Hawaiian LLD 353kc has been copied more than once - a distance of over 2500miles. The recommended "arrow" placement (position 5) of the Crystal Filter isn't particularly good for NBDs. I find that around position 8 gives better noise reduction and allows weaker signal copy. Once in a while, adjusting to 2 or 3 will increase the bandwidth and the "highs" and sometimes this helps with multiple signals on the same frequency.   
Feb 4, 2015 -
Newly heard NDB is another Hawaiian NDB, POA 332kc copied at 0550PST.

UPDATE: October 2, 2017 - Out of curiosity, I decided to connect the SP-600VLF to my 135' CF Inv-Vee with the feedline shorted and see what was on the frequencies below 200kc (the lowest that the loop will tune is 200kc.) Lots of various types of beacons and data signals of unknown origin everywhere. I think some of these are harmonics from various power line data or other switching or data sources that don't care what they are radiating. At 51kc there was a strong MSK station, probably USN. At 60kc was WWVB with its pulse-encoded signal. Jim Creek NLK USN MSK was very strong at 24.8kc followed by NAA in Cuttler, ME at 24.0kc and two other MSK stations, 21.4kc NPM in Hawaii and 19.8kc Holt in Australia. All of these USN stations were strong but NLK was very strong. Below 17kc there isn't much. A few signals that are unidentifiable. 12kc had some type of signal there (Russian?). Nothing was heard between 132kc to 136kc (a supposed ham band.) Nothing was heard between 160kc and 190kc (the Lowfer band.) Nothing was heard between 472kc and 479kc (supposed 630M ham band.) This was at 4PM local so JJY at 40kc wasn't received. Checked a few days later at 06:15PDT and heard JJY on 40kc with their CW ID. Also heard POA 332kc. Also checked 630M supposed ham band and heard nothing except DGPS signals (or harmonics of them.)

Modified the loop again, October 2018 - This time the pickup loop was increased to four turns and it was moved to three inches away from the tuned loop. More gain with the four turns and better selectivity with the increased distance between the pickup and the tuned loop.

UPDATE: November 5, 2018 - I had a sked with NO3M on 473kc at 1900 PST. I didn't think I'd be able to hear Eric since his QTH was in Pennsylvania - I've never even heard a NDB from Pennsylvania! Total surprise when I heard "CQ CQ CQ de NO3M NO3M NO3M K." Eric's signal wasn't strong, maybe S3 but it was Q5. I answered the CQ but Eric couldn't hear me. I was using the Hammarlund SP-600VLF and the six foot remotely tuned loop. My transmitter was the ART-13A with CU-32 loading coil to a 163' End Fed Wire. I was amazed that I could actually copy a ham signal that originated almost on the East Coast. As mentioned above,...the SP-600VLF is sensitive and it seems to work well with the loop now that I've modified the pickup loop. I did have a successful two-way QSO with NO3M on December 7th.


Regenerative TRF Receivers versus Superheterodynes on Longwave

In the early days of wireless communications, all transmissions were on longwave. After the signing of the Alexander Bill in 1912 moved the amateur operation to 200 meters or below, experimentation into the shorter wavelengths began. Ships and navigation remained in the longwave region, (even today most navigation and submarine communications remain in the LW spectrum.) After WWI, most receivers used were regenerative detectors with two-stage audio amplifiers. Later, TRF stages were added ahead of the detector to further improve weak signal reception. As designs progressed, the superheterodyne did not immediately replace the TRF regenerative receivers on LW. At first, superheterodyne designs used rather low intermediate frequencies that limited coverage of certain segments of the LF bands. The USN RAA LW superhet receiver from the early 1930s used four different IF stage frequencies to optimize performance and provide complete tuned frequency coverage (10kc to 1000kc.)  For full LW (typically 15kc to 600kc) coverage, the regenerative receiver had no such limitations. Later LW superhet designs moved the intermediate frequency above the LW bands to give complete coverage.

Regenerative receivers have some advantages over the typical superhet receiver on LW. For example, receiver internal noise - regen sets are quiet and don't add much noise to an already noisy part of the spectrum. The frequency conversion required in the superheterodyne can create substantial internal noise in the receiver that limits its weak signal ability on longwave. Also, since a minimal number of tubes are used in regen sets, thermal noise is at a low when compared to a large tube-count superhet. The regen set's ability to be set-up as an Autodyne Detector, that is to produce an oscillating condition without a BFO, is also an advantage. With a superhet it is necessary to use the BFO to set-up a condition where the carrier can be heard however the BFO in a superheterodyne can sometimes mask weak signals. Though most BFOs are very lightly coupled in early superhet receivers to prevent "masking" this is not always the case in modern receivers. Additionally, when the regenerative set is oscillating, it is doing so at the tuned frequency while a superhet, using a BFO, is actually providing an audible heterodyne by injecting an oscillator signal at the detector that is somewhere near the intermediate frequency. It is the level of the injection that is important to weak signal copy. >>>

photo above:
   1923 RMCA  IP-501-A during a LW performance test. The receiver is powered by a Lambda 6vdc 4A power supply and a RCA Duo-Rectron regulated B+ power supply. The -C bias is supplied by three AA batteries in series. The antenna used is a 80M ham inverted vee with the feed line shorted. Since the regenerative detector is set to oscillate for NDB copy, some RF energy will couple back to the antenna. By wrapping a pick-up wire around the antenna lead-in, a digital frequency counter can used to provide an accurate frequency readout. This set-up only works while the detector is oscillating (autodyne.) The IP-501-A is tuned to local NDB "NO" from the Reno-Tahoe Intn'l AP (NOTE: NO 351kc has gone "off the air" in 2013.)

>>>  Lack of Automatic Volume Control (AVC) in the regen sets is also an advantage as a high noise level can capture the AVC and decrease sensitivity. Normally, with vintage superhet receivers, most CW listening is done with the AVC off  for that very reason. Most superhet communications receivers will provide switchable AVC. However, some modern receivers, especially SWL portable types, do not have a switchable AVC provision leaving the listener at the mercy of atmospheric noise. Selectivity can be be achieved by use of audio filters in later sets or by advancing the regeneration control to the point where oscillation just begins in earlier receivers. Many early receivers also provide a coupling control for selectivity (and for setting "critical coupling" for optimizing the ratio of signal to regeneration at the detector.) By using the ear and listening for a particular tone frequency our own brain can be a very effective filter although this does require some practice to become proficient at. Another habit that old radio ops had was to copy using earphones. This will allow hearing  weak signals that are at the "noise level" - of course static bursts can be almost painful at times when using early sets without limiters. Most WWII USN LW receivers will have audio output limiters that function very well at keeping static bursts at a manageable level. More common (and modern) "clipping" noise limiters don't seem to work as well as Output Limiters and will allow "pops" and static bursts through. This is because the clipping noise limiter works on repeating pulse patterns - like auto ignition noise - rather than acting on a single, quick, intense pulse. An easy method to preserve your hearing is to keep the 'phones slightly in front of the ears. Notice in vintage photos of USN radio ops that the phones are always in front of the ops ears. This method has been used by experienced CW ops since the early wireless days (when static bursts were just about the only loud signals.)

Mentioned above, the RCA-built USN RAA longwave superheterodyne receiver was a gigantic, 465 pound receiver that used 14 tubes and had four different IFs that were individually selected by the bandswitch(s.) Four specifically tuned BFOs were also needed in the RAA. The four different IFs allowed for uninterrupted coverage from 10kc to 1000kc. The complexity and expense of the RAA forced the Navy to reconsider earlier, less complicated and less expensive longwave receivers. After the RAA, all Navy longwave receivers were either TRF with regenerative detector or TRF with tracking BFO. Of the latter catagory is the RBA series built for the Navy during WWII. These receivers use three cascade TRF amplifiers feeding a non-regenerative triode detector followed by three audio amplifiers - in essence, the typical TRF receiver of the late twenties. However, that's where the similarity ends. The RBA also uses a "tracking" BFO that tunes via an additional ganged section of the five-gang tuning condenser. This allowed the BFO to always be 1kc above the tuned frequency and provide the heterodyne necessary to demodulate CW. Also, the RBA featured a "tracking" auxiliary gain control that was gear-driven from the tuning mechanism and kept the gain level constant throughout the tuning range. The RBA was used by the Navy for about two decades after WWII ended and its superior performance illustrates what can be accomplished in TRF design when cost was not an issue - the RBAs sold to the Navy for $3000 a piece in the 1940s.

Now, all of the above isn't saying that a vintage superheterodyne can't do a good job on LW reception. When specifically designed for LW, with low noise tubes and circuits, a superhet can perform quite well on LW when used with the proper antenna. However, many superhets just added a portion of a LW band to a receiver that was really designed for HF. These types of superhets are common and their LW performance is usually rather poor. There are exceptions with the National HROs (using G, H and J coil sets,) the Hammarlund SP-200LX (aka BC-779) and the RCA AR-88LF (aka CR-91) being noteworthy as high performance superhets that do a fine job on their limited coverage LW bands.

Also, there are two well-known, vintage, ultra high-end, designed specifically for LW, receivers that were made for the military and for the laboratory. The Hammarlund SP-600VLF is a top performer with continuous coverage from 10kc up to 540kc and the familiar "SP-600" appearance. However, it isn't just an SP-600 with LW coils installed in the turret but rather it's a completely "designed for LW" receiver that uses the basic SP-600 physical appearance and mechanical features. Unfortunately, the "VLF" is a rather rare and usually expensive version of the SP-600 and, while the SP-600VLF is an exceptional performer, it does require a low-noise antenna and, for LW DX reception, it's really helps to have a low-noise location. The other "high-end" LW receiver is the Collins R-389 LW receiver but it's so rare (856 built) and so expensive that it has become better known as an ultimate "Collins Collector's receiver" than known for its incredible LW performance. The R-389 is a mechanically and electronically complex, double conversion receiver that mixes the incoming RF LF frequency with a VFO plus crystal oscillator to convert the frequency to an IF of 10mc which is then mixed with the same crystal oscillator to achieve the 455kc IF. This signal is then routed thru six IF stages using the same type of IF module used in the R-390 receiver. The remaining circuits and modules are the same as the R-390 receiver. The R-389 is another exceptional receiver but many times, its performance is reported as "adequate but not phenomenal." It's likely that many of the R-389 receivers in collections would benefit from a complete servicing since these complex receivers generally don't attain their high-performance capability unless they are maintained and aligned by competent techs. As with any LF receiver, a low-noise location is necessary for LW DX reception.

Many casual LW listeners aren't aware that all of the "top performing" LW receivers must be operated with some type of  low-noise antenna, even in a RFI-quiet location, to achieve DX reception on LW. In reality, most "high-end" LW receivers have about the same abilities and superior performance is more dependent on the operator's experience, the antenna type used and the receiving location rather than on the type of receiver being used. If the LW superhet user runs his receiver with a tuned loop antenna or a low-noise wire antenna like a Beverage, he will find the signal to noise ratio is greatly improved and, in a quiet location, he should be able to receive ample LW DX.


Selective Level Meters and Wave Analyzers as Longwave Receivers

Selective Level Meters and Wave Analyzers are test instruments that incorporate a tunable sensitive receiver with selectable filters and attenuators to drive a calibrated analog meter. These instruments are used for a variety of purposes such as measuring leakage or unwanted signal levels on transmission lines, testing response of various kinds of amplifiers, some types even provide a built-in signal generator for test signals. None of these type of instruments are designed specifically as Longwave receivers, however, some of them actually perform quite well in that function. I have used two Selective Level Meters as LW receivers, a Sierra Model 125B and a model made by Cushman. The Sierra 125B was a vacuum tube model and was fully operational with a good set of tubes and I had performed a full alignment. However, that particular model did not have a BFO to help locate weak NDBs. This made the Sierra 125B very limited in its usefulness as a LW receiver. I also had loan of another selective level meter made by Cushman. This was a solid-state model that did have an on-board BFO with USB and LSB capabilities. It didn't matter, I couldn't pick up any signals using it. The set's owner was also disappointed with the Cushman's performance as a LW receiver and he eventually sold it on eBay. By far, the best instruments for use as longwave receivers are some of the Hewlett-Packard Wave Analyzers.

I happen to have the HP 310-A version in which the receiver tunes from 1kc up to 1500kc. The 310-A also has selectable USB or LSB and AM detection along with 200Hz, 1000Hz and 3000Hz selectable bandwidths. Lowest scale sensitivity is 10uv FS meter reading (maximum signal level) although using this sensitivity depends on how much atmospheric noise is present. With a tuned loop antenna, 10uv FS meter can almost always be used. During high noise periods with a wire antenna, 30uv FS provides better noise immunity. In the "Relative" measurement position the sensitivity is adjustable for best response versus noise. The HP 310-A is a late sixties to early seventies vintage instrument with a mechanical counter providing the digital frequency readout.

photo left: The Hewlett-Packard 310-A Wave Analyzer. The mechanical digital readout is for receiver frequency while the long horizontal scale illuminates a red numeral depending on the sensitivity (max. signal) selected. The tags above the meter switch are USAF property identification tags.


photo right: The Sierra Model 125B Frequency Selective Voltmeter. The drum dial scale is at a "slant" because it is continuous tuning that has the scale spiral up as the drum is turned about four turns to go from 1kc up to 620kc. Lack of a BFO on the Sierra is a severe limitation for using it as a LW receiver

I find that the performance of the HP 310-A is very favorably compared with any of the vintage longwave receivers profiled in this web-article. The 310-A doesn't have a noise limiter - mainly, because noise was one of the things the instrument was designed to measure. However, manipulation of the sensitivity versus the atmospheric noise seems to do pretty well for coping with the lack of a limiter. Since this is a measurement instrument, no AVC is provided, so strong signals will over-drive the 310-A, especially when using a tuned loop antenna. Watch the meter and keep the measured signal level at about 75% to 95% of FS with the Relative Gain control. I have received hundreds of NDBs from all over North America on my HP 310-A, from DDP 391kc in Puerto Rico to LLD 353kc in Hawaii. My conclusion is that Selective Level Meters and Wave Analyzers are designed for finding and measuring leakage in systems, measuring frequency response or measuring unwanted signals on transmission lines and other similar applications. Some of these instruments are useless as longwave receivers. Read up on any instrument you intend to purchase for longwave reception and make sure others have had success using it for that purpose. The first two instruments I tried were of the "useless" variety, however the HP 310-A performs very well as a longwave receiver.

Other Vintage Receivers with Some Medium Wave and Low Frequency Coverage

All but one of the receivers profiled above were specifically designed for MW, LF and VLF coverage - generally 600kc down to 15kc. Many other receivers were offered in versions that covered a portion of either the MF or the LF spectrum. During the 1930s, many "All Wave" radios for the home tuned down to 150kc because there was so much to listen to then in that part of the spectrum. Also, a few models of communication receivers were offered with limited MW/LF coverage. Some of these versions were excellent performers while others were barely adequate. The following is a short list of some of the more common types of receivers. None of the receivers listed below cover the entire "longwave" spectrum of 600kc down to 15kc. 

National Co., Inc. - HRO - using coil sets G - 420kc to 200kc, H - 200kc to 100kc, J - 100kc to 50kc - Very good performer with long wire antenna or loop. These coil sets were generally optional equipment but the military versions did include a complete set of coils, including those for MF/LF coverage. Of these military versions, the HRO-W and the RAS are the most common. LF coil sets can be used in any of the HRO receivers but alignment to the specific receiver is required for best performance. Double preselection (two TRF amplifier stages) are used in all coil sets for the HRO. IF is 456kc on almost all versions. Notice that there is a gap in frequency coverage from 480kc to 420kc (coil set F covers 920kc to 480kc.) This was because of the HRO's IF of 456kc. The RAS used 175kc IF and that allowed it to cover from 195kc up to 500kc without a gap in the frequency coverage (the USN wanted complete coverage in the 400kc to 500kc range which the standard HRO couldn't provide.) The RAS receiver must be used with RAS coil sets identified as coil sets 1 through 7 on a metal tag on the coil panel. Later HROs, like the HRO-50 and HRO-60, can also provide excellent performance using the G, H and J coil sets. The LW coil sets for these later receivers are a bit more difficult to find and are usually somewhat expensive because of that.

Hammarlund SP-200LX aka BC-779 - covers 400kc to 200kc and 200kc to 100kc - Excellent with loop antenna, a bit noisy with long wire antenna (depends on your location.) Good dial accuracy. The BC-779 is probably the most popular of the military WWII versions of the SP-200 series. Some BC-779 receivers were built by Howard Radio Co. under contract. Band spread was not provided on the LF frequencies. SP-200LX is the designation used for any pre-WWII or non-military version of the "200 Series" receivers. IF is 465kc on all versions and double preselection is used on all bands. There was also a SP-100LX version that is an earlier version with the same frequency coverage but this version is rare.

RCA AR-88LF and CR-91/CR-91A - covers 550kc to 73kc (550kc to125kc on AR-88LF version) with SW coverage above 1.5mc - Excellent with long wire antenna or with a loop. Good dial accuracy. A heavy receiver weighing nearly 100 lbs in the cabinet. All steel construction is why. Stability was what RCA was trying to achieve and these receivers have virtually no drift. The AR-88LF versions were generally sent overseas during WWII and are somewhat difficult to find in the USA. The CR-91 is the USA-built replacement for the AR-88LF but it's very rare. Most CR-91s are actually the post-war CR-91A receivers that were built in Canada (RCA-Montreal.) IF is 735kc on all LF versions and double preselection is used on all bands.

The Ultimate Vintage Long Wave Receiver? - If you're looking to find the ultimate vintage LW receiver,...the one that's the most sensitive,...the one that can pick up weak DX signals through any sort of noise,...the one that doesn't require special antennas,...well,...unfortunately that receiver doesn't exist. There are very good performers and there are "not so good" performers but there really isn't one receiver that "stands out" above the rest as the ultimate vintage LW receiver. I've tested and used dozens of different kinds of vintage LW receivers and in my opinion the "best" of these types of LW receivers all perform at about the same level. While all of the receivers profiled in the first section of this article can perform quite well on LW, there are a few that standout as my "favorites" to use. My first choice overall would be the Hammarlund SP-600VLF-31 receiver. It's an easy to use, easy to maintain, sensitive LW receiver. An extremely close "second" is the US Navy RBA receiver. The RBA is somewhat difficult to maintain and difficult to set-up because of the separate power supply and armored cable but its sensitivity is phenomenal. My third pick would be the Collins R-389. It's a fantastic performer but it's a paragon of difficulty to maintain and expensive beyond belief. These three receivers are about the best of the vintage LW receivers because all three can detect very weak signals that are "in the noise." All three have direct frequency readout with illuminated dials, the RBA receivers have excellent Output Limiters that are very effective noise limiters and all three have excellent mechanical construction. However, even these three top vintage LW receivers can't perform well within certain environments or when LW receiving conditions are poor.

Regardless of the LW receiver used, for effective LW DX reception you absolutely need the following:  First and most important is a good receiving location that has very low RFI-noise levels (Radio Frequency Interference, e.g., manmade RF noise.) High RFI-noise areas will limit what even the best receiver can pick-up and separate from the interference. Second, a good low-noise antenna. An antenna that "picks up" a lot of RFI-noise will only compound a noisy location problem, making even the best LW receiver a poor performer. Even in RFI-quiet areas, using a low-noise antenna will benefit your reception. When you have a superb receiver operating in a quite receiving location with a good low-noise antenna then you absolutely must to use headphones for the audio output. Don't use the 'phones jack as the audio source. You must operate the 'phones directly from the 600Z ohm audio output of the receiver. You'll never hear the extremely weak signals using a loudspeaker. 'Phones are a must. Finally, you must have good receiving conditions and that means you do your LW listening during "the LW season." This would be late-Fall and Winter nights and early mornings (the "LW season" is usually between the Autumnal Equinox and the Vernal Equinox ). The following sub-articles detail some of these MW/LF reception problems and some of the solutions to noise and what types of antennas are best for successful LW reception.


What to Listen to using Vintage Long Wave Receivers


LW Propagation - The time of the year and hour of the day are important to successful DXing on LW. Although in theory LF and VLF propagation is generally considered to be mainly ground wave, most NDBs are actually in the medium wave band (MW) which is 300 kHz up to 3000 kHz. MW does have both ground wave and substantial sky wave propagation characteristics. About the only NDB DX reception is going to happen at night and up to just before local sunrise. Below 100 kHz, ground wave makes up the majority of the signal propagation, however losses due to absorption are highest during the daytime so best signals are usually a nighttime occurrence. Sometimes sky wave will still happen in the LF part of the spectrum and this also adds to nighttime's advantage for better reception. Although you can receive the Navy MSK VLF stations (19kc to 25kc) day or night, weaker LF stations, like JJY at 40 kHz, can only be received just before local sunrise and still nighttime west across the Pacific to Japan.

Due to the sun's position, its affect on the ionosphere and the intense noise generated by the sun's activity, winter nights are always best for reception on LF and MW (in the Northern Hemisphere.) Summer is plagued with countless thunderstorms that add intense noise to the LW spectrum - day and night. Usually by mid-September, the LW signals are getting better and the summer noise is becoming less bothersome. By mid-May, the noise is again increasing to the point where only the strongest signals can be heard. Therefore the LW listening "season" is usually considered to be between the Autumnal equinox and the Vernal equinox. Also, low noise LW conditions generally occur during sunspot minimum during the 11 year sunspot cycle. Increased solar activity, usually favored for HF DX, increases the band noise on LW. VLF is not usually affected by much of anything which is why it is used for 24 hour, worldwide USN communications. The US Navy MSK stations located around the world are always easy to receive with equipment that can tune low enough - 19kc up to 25kc.

Some of the Signals (Past and Present) below 500KC

Tuning around below 500kc offers some interesting challenges and a different kind of DXing. Nearly all signals encountered are either CW, MCW, RTTY or some kind of data transmission. There are virtually no voice transmissions except for a handful of foreign longwave BC stations. Here are some of the types of signals found below 500kc.

NDBs - An enjoyable part of listening below 500kc is receiving the many different Non-directional Beacon (NDB) stations that are located at many airports around the world. Airport NDBs operate continuously, 24 hours a day, seven days a week. The transmissions are nearly always in MCW using a 400hz tone (1020hz was popular in the USA but isn't used anymore.) The NDB station will transmit its assigned call letters in International Morse every few seconds. The NDB ID usually is a three-letter combination that often bears some resemblance to the airport location, e.g., CHD in CHanDler, Arizona. US NDBs that use only two letters for an ID are usually "marker beacons" located at the beginning of a runway. Often, marker beacons are not listed on NAV-AID websites and therefore are sometimes difficult to identify. NDB transmitter power is generally around 25 watts in the USA, however there are some US regional NDBs that run up to 400 watts and a few coastal "transoceanic" and Alaskan NDBs that run 1KW to 2KW. Some Alaskan NDBs also transmit TWEB or "voice weather" in addition to their call in MCW (RWO 394kc Kodiak, AK is one.)

Canadian NDBs will follow their station call with a "key-down" signal until the call is sent again. This makes all Canadian NBDs easy to identify. Also, most Canadian NDBs run substantially more power than the typical 25W US NDB, so their NDBs usually put out strong signals. Sometimes Mexican NDBs will proceed the ID with a "long dash" - not "key down," just a long dash, (I have heard this on GRN several times but not on other Mexican NDBs.) NDBs can be found from 190kc up to 529kc. Many NDBs are being "covered up" by powerful DGPS* signals within the same part of the spectrum (generally signals from 285kc up to 325kc are predominately DGPS signals in the Western USA.) Since the NDB signals are MCW, a carrier is always present on the assigned frequency. With the receiver BFO on, it is easy to locate the NDB carrier and then ID the station when the call is sent. Nearly always, there are multiple NDBs assigned to the same frequency so listening for different characteristics of the transmitted signal becomes part of the method of identification. Also, due to changing propagation, different DX NDBs assigned to the same frequency, will be heard during different listening sessions.

Once the NBD call letters are known, they can be checked against one of the NAV-AID websites. By entering the station ID, the websites will provide the NDB airport location, assigned frequency and sometimes the transmitter power. The best information source is  where you'll have to load either the call of the NDB or the frequency of operation into the search parameters and then the page will jump to the listing. You can also scroll down the complete listings of NDBs by frequency of operation. There are also notes regarding certain characteristics for some NDBs as reported by listeners. Classaxe provides the most up to date information on NDBs. Another navaid source for USA, Canadian and worldwide NDBs is . World Aero Data has almost all NDBs listed but you will have to click on the "Airport Call" to find the actual location. A lot of specific airport information can be gathered from worldaerodata. These two websites provide the "double-check" that is necessary to confirm the NDB ID heard on a specific frequency is the actual station received since there are usually several NDBs with the same call letters but never are identical IDs transmitting on the same frequency. Eventually, a list will have to be maintained in order to know when "new" NDBs are received.

Knowing International Morse - NDBs seldom send faster than 10 words per minute, so it's not really much of a challenge to copy their call letters, especially since the NDB call sign is sent "over and over and over." When the signal is strong and there's no interference, copy is easy, even if your Morse ability is limited. Can you still receive and identify NDBs if you can't copy Morse at all? More than likely the answer will be yes, mainly because NDBs send so slow and the NDB call is sent "over and over." Since many private pilots were barely Morse proficient (if at all) the intention was that NDBs would send slow enough that the "dots and dashes" comprising the NDB call sign could be written down, e.g.," _..   _..   ._ _. ," and then "translated" into the letters (DDP) that identify the beacon. Being fluent in International Morse is a major advantage when trying to copy several NDBs operating on the same frequency. It's also helpful when the signal is so weak that it's practically at the same level as the noise and is fading into oblivion. I'm not saying that you have to be able to copy 20WPM in your head while having a conversation with someone else on the telephone but a good code receiving ability will ultimately help fill your NDB log.

Even When You're Morse-Fluent - Every so often you'll come across a NDB sending incredibly bad Morse. From incomprehensible character formation to just plain poor spacing, it all adds up to an almost impossible call sign to copy. Fortunately, this only applies to a very small percentage of NDBs. Most beacons send excellent Morse but eventually you'll hear a call sign that defies copy. When this happens, copy the call as best you can but be sure to note the frequency of operation. Later, you can use "" to search on "the frequency of operation" to see if the call letters are "rearranged" due to poor spacing. There are several NDBs that have this problem, LDG 296kc is a good example. I've copied this NDB as "DGL" many times because of their spacing problem. Poor character formation is almost as much of a problem with NDBs like MNC 348kc sounding like "NNC" or POY 344kc sounding like "POC." Be sure to log the frequency along with the call. That way you might be able to decipher a questionable call sign when checking your reception list versus the NAV-AIDs. Again though, 99% of the NDBs send excellent Morse.  

*DGPS - Differential GPS,...see section below.


Other Beacons - There other kinds of beacon signals that will be received on LW. Sometimes these are marine buoys that provide some navigation or hazard information in bays, lakes and other waterways. Most of the time it's next to impossible to find out the location of these particular signals that are obviously beacons of some kind. If the MCW ID is not listed in the NAV-AID sites, it does not mean that the signal received is not a legitimate beacon. Even legitimate airport NDBs sometimes aren't listed in any of the NAV-AIDs, like some "marker beacons." This can be an oversight or sometimes it's a new NDB (yes, there are new ones starting up with some regularity, even today - LYQ in Manchester, TN, for instance, just started up in 2008.) If the NDB heard is not listed in the NAV-AIDs, then try a web search on the NDB ID or try some of the web NDB logs to see if other listeners have heard the same station. Sometimes, though not too often, complete information on the NDB is found by this method. Part of the interest in LW listening is receiving weird and strange signals that are a challenge to identify.

On the future of NDBs - Current US regulations state that if an NDB transmitter fails, the airport is not required to repair or replace their NDB station. Every month, more and more US NDBs are "retired" as obsolete technology since there are other more modern navigation signals available that are more accurate. However, many airports do select to maintain their NDBs as the operation costs are negligible and it provides a safety backup if the pilot has problems with his other air navigation equipment. It's up to the airport to decide if they want to continue to provide their NDB signal as part of a tradition of air navigation. Remote airports, especially in Alaska and in the USA along the Canadian border, seem to be more inclined to keep their NDBs in operation.

photo left:
   One of our LW receiving stations when we were in Virginia City - the WWII Navy RAZ-1. The small black box is the "remote tuning" for the loop antenna.

DGPS Signals - DGPS, or Differential GPS, uses a somewhat local transmitter signal that works with satellite GPS to correct intended errors in the GPS satellite information. When GPS was being developed there was a concern that an enemy could use the GPS satellite information to accurately aim and deploy various types of weapons. To prevent accurate information from being available directly from the satellite, errors were built-in. These errors could then be corrected using local transmitters sending "correction" signals. This initially was for military uses but eventually also was to allow civilians to utilize the GPS information. GPS evolved over the years but still the DGPS correction transmitters are being used. There are 85 DGPS transmitters in the USA (some of which were converted from the 85 GWEN* nodes by the USCG.) Most are located along coastlines and some major waterways. Canada also uses DGPS along its coasts and along the St. Lawrence Seaway. There is a specific frequency band where the DGPS signals are located, 183.5kc up to 325kc. It depends where in the USA you are located just how much interference the DGPS signals impose upon reception of NDBs. Here in the Western USA, most DGPS signals are concentrated from 285kc up to 325kc. There are a few in the lower part of the DGPS band but the strongest signals are centered around 300kc (in the West.) As more and more demand for civilian GPS uses increase, expect to encounter more DGPS signals.

NOTE: Although I hate to admit it, I've used the DGPS signal on 314kc as a receive "test signal" many times. That node is located near Sacramento, California and it's extremely strong here in Western Nevada. Since I know it's on 314kc and very strong, it makes an ideal "test signal" for the middle of the "NDB Band." When FCH 344kc in Fresno, California shut down (Jan 2018) I no longer had any NDB signal strong enough for daytime copy. Our strong local NDB, NO 351kc in Reno, Nevada, had shut down in August 2013 (and it's really missed.) DGPS 314kc is very strong and does provide a handy "test signal" for daytime use.

*GWEN, or Ground Wave Emergency Network, was a LF military communications network that utilized of 85 transmitter nodes located within the USA. Each node consisted of a high power LF transmitter in the 170kc to 190kc part of the spectrum, a 200 ft tall tower/antenna and all of the support gear for providing emergency communications post-nuclear attack. Supposedly, LF was not vulnerable to damage from the EMP of nuclear detonations and could theoretically survive as an operational system. Military and presidential comms to SAC were intended but the system had many problems and, by 1994, had lost funding. The system was eventually shutdown. Many of the nodes were converted to DGPS use.

More Longwave Signals

Longwave Broadcasting - In addition to NDBs, there are foreign longwave broadcasting stations. These are only located in Europe, Africa or Asia. The stations run incredible power levels. One million watts of carrier power is common for longwave broadcast stations. Even though their power levels are extremely high, the signal's propagation faces severe losses and most longwave broadcasting is intended for regional service only. Here in the western part of the USA, it is possible to receive a couple of LW BC stations but those stations are never strong signals and rarely can the program be enjoyed. The strongest and most often received station here is Radio Rossii, located on Sakhalin Island (North of Japan) broadcasting on 279kc at a power level of one million watts. During the winter months in the early morning (~5AM PST,) Radio Rossii is very strong (for LW BC) and can be heard playing Russian pop-jazz music and reading their news service. These are always reports in Russian read by alternating male and female announcers with a short musical interlude between stories. Other LW BC stations are very weak and many times only the carrier can be received, the modulated information being too weak to really understand or even identify. UPDATE 2017: Radio Rossii on LW is gone for good. In fact, all Russian Long Wave broadcasting has stopped as of January 9, 2014. Only a few LW BC stations are active in Asia. Turkey has one and one in Georgia. Apparently these LW stations are too expensive to operate and maintain along with enduring a continuing loss of listeners that have gone to satellite or Internet services.

Longwave Broadcasting's Future - It doesn't look good  -  Most of Asia no longer broadcasts on LW. Europe has about four stations still operating. The BBC-4 LW station is still running a vacuum tube transmitter and claims when the last tube goes, they are permanently off the air. They claim to have "bought up" all of the spare tubes available in world a few years ago,...and, apparently these tubes can't be rebuilt (more likely the BCC doesn't want to spend the money to have the tubes rebuilt.) When the Irish LW BC station, RTE-Radio One, shutdown a few years ago there was an enormous protest from the Irish in Britain that eventually got RTE-Radio One to reverse their decision to shutdown. The arguments to shutdown all LW BC are based on technology in that higher fidelity programming is available on Medium Wave (AM BC) or FM BC or Satellite or even the Internet. However, ardent LW listeners say "so what?" They don't want to change their listening habits. Even if the LW BC technology has its limitations it doesn't matter since most listeners aren't using new receivers anyway. Many are still using their old vacuum tube radio purchased decades ago. Expensive operation and maintenance cost when power level is at one million watts and the transmitter is of vacuum tube design seems to be the ever present threat that shuts down the LW BC station. At the present, the only thing keeping LW BC alive is their devoted listeners and those include still many maritime listeners. However, the end is probably "in sight" for LW BC. None of the stations want to upgrade their equipment since the future of LW BC is so bleak. Also, in many cases, the real estate that the massive antenna systems inhabit is probably worth more to the governments than maintaining "an obsolete technology" that benefits few and costs them so much to operate.

"Lowfer" is a nickname for the LF enthusiasts that transmit 1 watt signals to 50 foot antennas in the 190kc to 160kc part of the LF spectrum. A license is not required to operate these transmitters because their effective radiated power (EIRP) is so low. The limitations have resulted in very clever ways of extracting very weak signals out of the noise in that particular region of the spectrum. QRSS, or very very slow CW, is one method used. It is so slow that a computer usually monitors the signal for several hours (all night) to assure that copy is possible. Other computer programs are also used to make possible copy of these extremely weak signals. Sometimes, when conditions are favorable, two-way "human" CW contacts do occur. Those are usually referred to as "Real Morse Communications" since so much on this particular band is computer driven and monitored for transmission and reception.

Amateur LF Operations - The USA allows hams to operate on 630 meters (472kc to 479kc) in CW or data modes with five watts EIRP. Also, 2200 meters (136kc) can also be used with a limit of one watt EIRP. In other countries, 136kc is a ham band that can be used for fairly high power transmissions although foreign power limits are probably not using EIRP measurements. EIRP is Effective Isotropic Radiated Power and it takes into account that most antennas available to hams will be inefficient on long wave. EIRP allows hams to estimate how much RF power to apply to their antenna based on several physical factors applied to the antenna to achieve five watts effective radiated power. It isn't the actual power input (which is usually much higher) but rather the effective results of that RF power applied to an inefficient antenna.

Several years ago, 22 experimental licenses were issued by the FCC under the call WD2XSH/xx. These were licensed individuals that are carrying out experimental transmissions around 500kc (usually 508kc.) The limitations were 20 watts EIRP. About half of the 22 licensees eventually got "on the air" but signals were scarce. In the West, WD2XSH/22 in Sweethome, Oregon was very strong and easy to copy. These signals were CW, not MCW. UPDATE: I haven't heard any amateur activity on 508kc for some time now. It seems that the spectrum around 500kc is now being used by commercial or military users. - 2017  UPDATE: Further down this page are more details on the 630 meter and 2200 meter ham bands along with more information on FCC Experimental License Grants - 2017

Time and Navigation Signals - WWVB (60kc) and JJY (40kc) are both pulse encoded time transmissions. JJY will identify their transmissions in CW at 15 and 45 minutes after each hour. WWVB provides no identification. Both WWVB and JJY can be received better if the BFO is on to demodulate what is basically a CW-type signal. There should be no problem with WWVB as its signal is extremely strong anywhere in the USA. JJY is a relatively strong signal in the Western USA in the early morning hours.

Loran C - All Loran C stations used to transmit on 100kc. The Loran C signal consisted of a precisely timed series of rapid pulses that both identified the station (as Master or Slave) and also allowed all Loran transmitters to be on 100kc simultaneously. The timing was critical and controlled by cesium-atomic clocks at each station. The shipboard navigation receivers were capable of identifying Master from Slave stations and designed to time the propagation delay based on "knowing" precisely when the pulses were sent and "timing" when they were received. Using the Master signal plus one or more Slave signals allowed the ship's navigation receiver to triangulate the wave fronts and determine their intersection point and the ship's position with an accuracy of around 50 feet, which in the ocean was pretty close. All Loran-C stations were shutdown in 2010 in what was mainly a political move that eliminated the last terrestrial-based, long-distance navigation system in favor of satellite-based GPS navigation.

Computer Programs - There are several computer programs available that will demodulate many of the data transmission-type LF signals and allow the user to "view" what kind of information is being transmitted. In some cases, weather maps and weather reports can be printed out from NAVTEX. SeaTTY is one such computer program. USN MSK signals can't be decoded without special equipment, data reassembly programs, encoding data and other sophisticated encryption/decryption information.

VLF Stations (Signals below 30kc)

photo above: SAQ in 1925. From "Radio Broadcast" - March 1925

SAQ - Grimeton, Sweden

Nowadays, SAQ is probably the best known VLF station since they periodically run the only operational Alexanderson Alternator in the world. The mechanical transmitter can produce up to 200KW of  RF signal on 17.2kc. The antenna system uses six 425 ft. tall towers supporting eight horizontal cables with six vertical drops. Each cross arm on each of the towers is 125 ft. across. 

SAQ was originally going to be built during WWI for communications to Great Britain, however delays postponed SAQ's completion until 1924. Communication to Great Britain and the USA was SAQ's primary use in the twenties and thirties. More radio transmitters were added to the facility over the years and by the late forties, Sweden was considering scraping the Alexanderson Alternator. Fortunately, it was instead preserved and maintained, eventually becoming a museum, as it still is today. SAQ operates twice a year. Once on Ernst Alexanderson's birthday (Alexanderson Day) in June and once on Christmas Eve.

SAQ is difficult to receive anywhere in the USA. Upper East Coast USA is about the only location that generally can receive the transmissions, although one report of reception did occur in the Central Midwest one time. Also, SAQ has been heard in Alaska twice. The difficulty has to do with the 17.2 kc frequency which to successfully receive requires a superbly quite location and an excellent-efficient antenna. Mostly, it's the noise and the fact that SAQ is a third of the way around the world that makes reception virtually impossible in the Western USA.

For more information including videos on SAQ, go to their website at  

UPDATE: Oct. 2018 - I've heard that SAQ has been working on their antenna system to increase the effective radiated power. Supposedly they found several helixes were shorted due to corrosion. However, I can't find any confirmation of this work on SAQ's website. The website does however state that SAQ doesn't run the full 200KW but is usually running 85KW when transmitting on Christmas Eve and Alexanderson Day. Perhaps this accounts for the absence of confirmed reception in the Western US.

UPDATE: Dec 24, 2018 - If you're planning on trying to hear SAQ's Christmas Eve transmission you should know that the transmission this year was actually Christmas Eve Morning, happening a 0900 hrs local SAQ time (which was UTC + 1hr.) To hear the transmission in the USA would require listening six hours earlier EST, or 0300 EST and nine hours earlier PST, or 0000 PST. There were several reports to the SAQ website from the USA this year. 

U.S. Navy MSK VLF Stations

The US Navy has several MSK stations operating from just below 20kc up to around 80kc, used for world-wide communications with the Navy submarine fleet. MSK is a multi-layered, very narrow-shift FSK, called Minimum Shift (Frequency) Keying or MSK, a signal with only a few cycles shift and four layers of split-data combination to allow high-frequency information to modulate a low frequency of operation. Additionally, all transmissions are encrypted, so even if you could recombine the data, demodulating the MSK signal wouldn't provide anything understandable. There are two enormous VLF Navy stations operating in the continental US, one in Cuttler, Maine, NAA and one in Jim Creek, Washington, NLK. The two main continental US stations employ huge antenna arrays and can run close to 2 million watts. At Cuttler, two 500KW transmitters are set up on slightly different frequencies (only a few cycles,) one for mark and one for space (assuming RTTY coding is still used.) Each transmitter runs to one of two (North and South) six panel antenna arrays that are over 6000 feet across. Each panel is diamond shaped and the six panels form a "six-pointed star" shaped antenna system called a "trideco" system. 62 miles of one-inch diameter cables are used in the entire array. Each antenna array (six panels) is supported by 13 towers ranging from just under 1000 feet in height to just under 600 feet in height (26 towers total.) An incredible 6200 MILES of wire is used for the radial system that runs out into the sea surrounding the peninsula. For maximum power, two additional 500KW transmitters can be used bringing the total power up to 2 million watts. For de-icing the antenna array, a 60hz power plant capable of supplying 11,000KW (11 million watts) is connected to the antenna after the transmitters are disconnected. Special copper alloy cables and some tubular cables are used in the antenna array to provide enough resistance for the 11,000KW to rapidly de-ice the cables (usually 3 mega watts is used for de-icing operations.) Since their exact frequencies are published, tuning the the Navy stations NAA from Cuttler, Maine on 24.0kc or NLK from Jim Creek, Washington on 24.8kc, for example, will provide a good test for your receiving set-up. It's very rare not to be able to hear either Cuttler or Jim Creek - at anytime of the day or night. 
                                                                                                        photos from QST October 1961

photo above
: This huge variometer is wound with 4" inch diameter litz cable. It is used along with a helix and an inductive reactor to tune the NAA transmitters to the antenna arrays. This variometer is actually tuned remotely from a control station located about one mile away. The entire antenna array (both North and South) spans approximately three miles. NAA went on the air in 1961 but NLK in Jim Creek, WA is actually the older VLF station having gone on the air in 1953. NLK runs 1 million watts to a dual antenna array that spans a valley between two 3000 ft elevation mountains in Washington.

Additional USN MSK Stations - NPM operates on 21.4kc coming from Lualualei, Hawaii. NPM is a USN MSK station running around 550KW to an ground-isolated vertical antenna with wire capacity hat system. NPM is usually a strong signal in the west. Also, on 19.8kc is Harold E. Holt, a MSK station from Exmouth, Australia. Holt is a USN station that is operated by the Royal Australian Navy. The Holt antenna is a single trideco (six pointed star) type. Holt can usually be heard in the west, not as strong as NPM ,but still it can be heard. On 25.2kc is NML, a USN MSK station operating from Lamour, North Dakota. NML is usually strong here in the west but it's operating frequency is very close to the incredibly strong NLK in Jim Creek. Sometimes it's difficult to tell where NLK stops and NML begins. The USN also has various other MSK stations that operate on random schedules and frequencies. I've heard MSK signals with some regularity on 51kc. This used to be a USN station located in Dixon, California but it's regular operation was shutdown several years ago and now it may be in the "portable-test-emergency" type of operation.

Amateur Operation on 630 Meters and 2200 Meters in the USA 

As usual,...there was a lot of opposition to having US amateurs transmit below 1800kc. It took five years to get FCC approval but still there's some "red tape" in the form of contacting the Utilities Technology Commission for final approval of your intended operation. The ultimate factor in the UTC decision for each individual ham operator will be his station's physical location. Online forms and e-mail makes the process of dealing with the UTC easy.

GOOD NEWS! - 630 Meter Amateur Band Proposal - As of February 2012, there is a proposal to create a world-wide amateur band dubbed "630 Meters." Actually, the proposal is for 7kc between 472kc and 479kc. Initially 1 watt effective radiated power was proposed but there is some indication that maybe that will be raised to 5 watts EIRP - essentially the effective power radiated from the antenna. Since nearly all of the antennas that would be possible for most amateurs to construct would be short in relation to the wavelength, the efficiency of those antennas would be compromised. Therefore, even though the EIRP might be 5 watts, because of antenna inefficiency it might take 100 watts of RF input to achieve 5 watts of EIRP. There are other restrictions that mostly involve other countries where interference with NDBs might be a problem. Also, at the moment there doesn't appear to be any details about the modes of transmission that can be used. Likely, due to the nature of the wavelength, transmissions will be restricted to CW or data transmissions - similar to the 30 meter amateur band in the HF range. The whole proposal has to still go through several steps to become official so it looks like the earliest that amateurs might be able to use "630 Meters" will be early 2013. (I was optimistic at this time.)

Five Years Later - Here's the Process - It's become a fairly easy process to get on 630M or 2200M. As far as the FCC is concerned, general and extra class hams can operate on 472kc to 479kc in CW or data modes and run 5 watts Effective Isotropic Radiated Power, otherwise referred to as EIRP. 2200M is 136kc and the modes are the same but the power limit is 1 watt EIRP. You don't have to contact the FCC about operating either band. The FCC has deferred final approval to the Utilities Technology Commission (UTC.) The UTC is a political lobby concern whose primary interest is to promote business and commerce for the various Utilities. They aren't particularly interested in ham radio unless it adversely affects the operations of the various utility companies. The UTC concern is interference with Utility troubleshooting data and other data that is sometimes on some types of power lines. Whether or not an individual ham would cause interference (at 5 watts EIRP) is dependent on their station's physical location in relation to data-carrying power lines. The UTC requires your station location to be more than one kilometer from any data-carrying power lines. The UTC requires your station antenna location referenced by GPS coordinates in degrees, minutes and seconds. From that information, they either approve your intended LW operation or not. The UTC website provides a form that can be filled out online and sent automatically to the UTC. If you don't hear anything back in the form of an e-mail within six weeks (howcome so long?) then consider that your station location is fine and "you are approved." Assume that you will be contacted by the UTC by e-mail if you are within one kilometer of data-carrying power lines. The online form allows for simultaneous approval for both 630M and 2200M operations.  

Here's the link for the UTC online form:

Operating Vintage Gear on the 630M Band

630M Success! - I set up a sked with Mel, K6KBE (QTH: Ione, CA) to see if he would be able to copy my station on 473.5kc. Our sked was for 0600 on March 15, 2018. I was to send CW consisting of "V", "TEST", "de WA7YBS" and QSL information. The transmission lasted about five minutes with all of the text repeated three times. Mel reported his reception to me via e-mail and indicated that he heard me "come on" at 0600 "straight up." RST was 419, which doesn't sound that great but, on 630 meters at a distance of just over 100 miles, that's success. Mel is working on his 630 meter antenna which still needs a loading coil to function correctly. Weather has been his hold up. When Mel is able to transmit we'll go for 2X Morse on 630M.

Successful two-way CW on 630 Meters! - Mel and I set up a CW sked for 0600 for April 2, 2018. Mel was using a homebrew transverter and a "loaded" 75 meter antenna. I called "K6KBE de WA7YBS" at 0600 and Mel came back with a RST 549 signal that sounded strong and in the clear. Conditions were good at this point. Mel gave me a RST 549 also. Next go 'round the QRN started up but copy was still solid. Mel's transmission was that "QRN got u" and he was missing quite a bit of what I sent. Our 73s completed the short QSO. Just over 100 miles and a two-way CW QSO on 473.5khz.

That night, at 2000 PDT, there was a West Coast 630M "get together" on CW 473.5kc. I heard W0YSE tuning up but he was too weak to copy. He was answered by K6KBE and Mel's signal was incredibly strong, 589 or better. I had the loop antenna pointing SW in Mel's direction which obviously helped his signal and was probably why W0YSE was too weak to copy (YSE's QTH is in Washington state, should have been pointing N.) I know,...why didn't I move the loop? A six-foot loop in the house is pretty difficult to reorient.

                                           630M Log for 2018-2019 Season               X = Indicates Successful Two-Way QSO

Nov 5, 2018 - Sked with Eric NO3M, 473kc 1900PST, no 2X, his RST 539, my signal couldn't be heard. His QTH: Pennsylvania
                 X   - Worked Ed KI6R, 473kc 1915PST, his RST 569, my RST 569, his QTH: near Sacramento, CA

Nov 23, 2018  X - Sked with Ed, WØSD at 20:10 PST, 473kc, his RST 539, my RST 449, his QTH: South Dakota, local QRN due to wind from weather front moving in
                        X - Worked Larry, W7IUV at 20:20 PST, 473kc, his RST 579, my RST 579, his QTH: Washington, good signal
                      - Heard KDØVBR calling CQ, RST 579, his QTH: Colorado - couldn't answer because of pending sked
                      - Heard Eric NO3M calling CQ, RST 549, his QTH Pennsylvania - couldn't answer because of pending sked

Dec 4, 2018 - Heard Eric NO3M calling CQ, RST 239, returned call but no copy - condx good, low noise
                       Heard WØPXJ calling CQ but QSB down to nothing
                       Called CQ three times 20:15PST, no answers

Dec 7, 2018  X - Worked NO3M, Eric - finally, a successful two-way. 19:15PST his RST 439 with QSB and QRN, 473.8kc - second exchange best sigs. His QTH: Pennsylvania

Dec 8, 2018 - Sked with K9KFR, Bob -  473.5kc 19:30PST not successful. Busy night on 473.5kc.

Dec 13, 2018 - Sked with K9KFR - 473.5kc 19:30PST not successful. QRN was intense and signals non-existent 

Dec 22, 2018  X - Worked Ed KI6R at 19:15 PST on 473.5kc - Very strong signal, RST 589. My RST was 579

Dec 26, 2018 - Sked with W6DJX in Lancaster, CA on 476kc at 19:30 PST. Heard Hank about RST 429. He didn't copy me

Dec 27, 2018 - Sked with W6DJX on 473.5kc at 19:15 PST. Hank was RST 549 here, he could hear me - barely, couldn't really copy me though.

Jan 10, 2019 - Some interesting conditions on MW today. I was doing some follow-up testing on the R-389 receiver after a recalibration and noticed that MOG 402kc Montegue, CA was coming in quite well  at 1530 hours PST (the sun was still high up though it was late afternoon.) A quick scan of the tuning range from 400kc down to 325kc turned up some interesting copy. QQ 400kc Vancouver Is. BC, CAN, SX 367kc Cranbrook, BC, ZP 368kc Queen Charlotte Is., BC, NY 350kc Enderby, BC and DC 326kc Princeton, BC. I've received British Columbia NDBs during the afternoon before, so that wasn't too much of a surprise. The real surprise was VT 332kc from Buffalo Narrows in Saskatchewan, Canada - during the day! Most Canadian NDBs run substantially more power than their 25W USA counterparts. Most Canadian NDBs are running between 400 watts and 1000 watts. But, Canadian NDBs use relatively small antennas just like their USA counterparts. I was using the 135'x99' "T" antenna. Though the R-389 is an excellent LF receiver and the antenna is a pretty good performer, certainly great conditions were the primary factor in this unusual daytime reception.


WA7YBS 75M & 630M Station

The station consists of two Hammarlund SP-600 receivers. The top receiver is the SP-600VLF-31 tuning from 10kc up to 540kc. The bottom receiver is the Hammarlund SP-600 JX-21 tuning from 540kc up to 54mc. The small box to the left of the JX-21 is the remote tuning for the six-foot loop antenna used on 630M for reception. The HF receiver output is to a floor speaker. The LF receiver output is to 600Z ohm 'phones. 

The transmitter is an ART-13A with O-17/ART-13A LFO installed allowing operation from 200kc up to 600kc. On top of the ART-13A is the CU-32/ART-13A Antenna Loading Coil. The CU-32 allows the ART-13A to match a variety of antenna types on LF. Both the HF output and the LF output from the ART-13A are routed through the CU-32. In my setup, the output of the CU-32 is connected to the HF antenna when "FIXED ANT" is selected and is routed to the 630M antenna when "TRAILING ANT" is selected. The silver box to the left of the ART-13A is an auxiliary condenser that aids in loading the transmitter on 75M. The J-38 hand key is for LF-CW and the mike is for HF phone. LF transmitting antenna is an end-fed wire 163 feet long. HF antenna is a 135' CF Inv-vee with 96' of ladder line to a Viking KW tuner.

E-mail for Sked: WA7YBS 630M CW Sked

Effective Isotropic Radiated Power? -  Why use Effective Isotropic Radiated Power to set the power limit of 5 watts? This regulation is a method to limit the EM radiation of the transmitted signal to a certain level by control of the relationship of the RF power input to the antenna versus the antenna's physical size and how that size relates to antenna efficiency. Consider that a full-size 630 meter half-wave antenna is over 1000 feet long. This type of "full-size" antenna might actually exhibit a slight gain when compared to an isotropic radiator (dependent on other losses.) Therefore, the power input would have to be 5 watts to stay within the regulations (assuming no other losses.) With a full-size, efficient antenna, even just 5 watts input could result in a formidable signal on CW. However, an antenna that will fit onto a typical city lot will be very inefficient at 630 meters and therefore would exhibit a considerable loss rather than gain. That's how the RF power input to a "small" antenna can be fairly high and yet only result in 5 watts EIRP. Think of the small, inefficient antenna as being like a "dummy load." You can input lots of RF watts into a dummy load and the dummy load does radiate a few feet but it isn't an efficient radiator. So, to stay within the regulations, one has to estimate the efficiency of their antenna and then calculate the amount of RF power input to that antenna versus its efficiency that would result in five watts EIRP. The efficiency is primarily determined by antenna size, antenna height and antenna resistance. There are other variables but it's best to ignore those since they involve soil conductivity, losses due to nearby objects and other things that "vary" all the time. The best info I could find is at under "Antennas for 630 Meters" and "EIRP." The formulae are explained in detail and four "real antenna" examples are shown to help answer "the EIRP question" for your particular or proposed set up.

Experimental Licenses -  I copied WH2XVN on 183kc on November 3, 2017 just before 06:00. The beacon-type signal was in CW and quite strong. Although the signal was within the so-called Lowfer band it was obvious that the transmitter and antenna consisted of more than 1 watt to a 50 foot radiator. Although Lowfers have those limitations, an experimental license allows the operator much better options for their LW experiments. It's not uncommon for experimental license grants to be for 20 watts ERP. So,....what about an experimental license? Read on,....

Experimental License Grants from the FCC are not "amateur licenses." You have to have a specific purpose or experiment that is described in the application. You have to describe your specific location, your station and your antenna within the application. You should be either a college or university,...or maybe a business that does R&D work. In other words, need a "good reason" for applying ("amateur communications" is not a good reason.) You can submit your request to the FCC "on line" and the cost is $65. Again,...these are NOT amateur licenses, they are licenses to conduct research, experiments and testing and all of your intended equipment and operation has to be described within the application. Grants are for 24 month periods that can be renewed,...maybe. Time from submitting the application to receiving the grant is from one to three months.


Dealing with LF RFI-Noise

The Longwave part of the RF spectrum can be very noisy with intense static making copy difficult. In an extreme RF noise generating environment maybe all that will be heard is intense "buzzing" any where you tune. These factors can pose anywhere from difficult to solve problems up to impossible to solve problems when using any type of equipment to tune in LW signals. So, does vintage LW gear respond any better or is it actually worse when used in a noisy environment? Most WWII LW equipment will have some kind of noise limiter and also some filtering though they may be of little use against the types of noise encountered today. Fortunately, most of the intense noise found on LW is originating from our own houses. Light dimmer switches are notorious for producing a loud "buzzing" RFI on LW. Certain kinds of controllers that have neon pilot lamps (the orange glowing light) can also create RFI noise. Florescent lighting, certain types of illuminated clocks, computers and monitors, burglar alarms, grow-lamps, "wired" smoke-detectors, switching power supplies including some types of "wall wart" power supplies and some types of CFI lamps - all of these (and probably more) can produce RFI noise. Additionally, modern efficient furnaces that are multi-stage and modulate the blower speed can cause some RFI. This generally is heard as a changing pitch to the RFI as the motor speed changes. The newer the furnace, generally the less RFI will be encountered. RFI is also dependent on how the thermostat controls the blower and burner modulation. Although the list of RFI appliances keeps increasing and sometimes it seems like an impossible challenge, cleaning up our own houses for RFI noise is the first step towards successful receiving of LW DX.

Another noise producer is street lamps - not when they are operating correctly but when they are malfunctioning. Usually before the street lamp goes out altogether it will cycle on and off with a time interval of about 30 seconds to one minute on the start-up cycle. During this time intense RFI is emitted. It's amazing how far away the malfunctioning street lamp can be and still create RFI at your location. Expect intense RFI from a street lamp within your block. Fairly intense RFI from two to three blocks away and nuisance RFI from four to five blocks away. Some receiver noise limiters can reduce the interference but early LW receivers with no filters are useless during the lamp's start-up cycle. Most of the time the failing street lamp will cycle on and off every couple of minutes, all night long. Normally, if you call the power company they will come out and replace the failing lamp. You will have to have the street lamp ID number that is located on the underside of the assembly by the lens and also the street location (the ID number is visible from the ground looking up.) Fortunately for LW listening, the most intense RFI from street lamps is located in the frequency range from about 450kc up to about 4000kc.

Some of the LF RFI noise is on the power lines. There is a tremendous amount of data that is "riding" on the AC power lines. This is in the form of some controlled-carrier information, test and troubleshooting data, time setting information and, in some areas, broadband on the power lines. Some of the data exchanging on the power line is via the "smart meter" that has replaced the old electro-mechanical power meters can also cause RFI. The quieter your receiving area is, the more likely it is that you'll notice some type of power line noise, especially if you use an end-fed wire antenna.

Since there are so many LF RFI noise sources today, especially within urban areas, just about the only practical relief will be by using a tuned-loop antenna. In extremely noisy locations the only solution might be to use a shielded-magnetic loop antenna. The shielded-magnetic loop antenna will use a non-ferrous metal loop-tube that almost entirely encloses the loop antenna wires that are inside. Since the antenna is electrically "shielded" but not magnetically "shielded" it responds mostly to the magnetic portion of the electromagnetic signal. Since most man-made RFI is electrical in nature, that noise is shielded by the loop's enclosure. However, all shielded loops will have some kind of signal amplifier that is either "tuned" or is somewhat "broadband" due to the limited response because of the shielding that almost entirely encloses the antenna itself. In many urban areas, only these types of antennas can provide relief from RFI and allow reception on the lower frequencies. Unfortunately, most commercially-made shielded loops are fairly expensive (~$500 and up.) In less severe noise locations, a simple tuned loop can provide a major improvement over a wire antenna and allow reception of very weak signals. Remember, none of these loops will produce stronger signals at the receiver if compared to a large wire antenna. However, in a RFI-noisy area, the loops will provide a much lower noise level and allow you to hear weaker signals. In a RFI-quiet area, a large wire antenna will provide strong signals significantly above the noise and will probably out-perform the loop.


Tuned Loop Antennas versus End-Fed Wires or Other Wire Antennas

Though LW stations can be tuned in using almost any type of antenna, a fairly large "Tuned Loop" generally provides the user with low noise reception due to its high Q, high selectivity. Another advantage is the ability to null out noise if it is from a particular direction. Most man-made noise will be somewhat directional and possibly could be nulled out. The selectivity of the loop will help with atmospheric noise by increasing the receiver's response to the tuned frequency and increasing the signal to noise ratio. However, the loop antenna must be physically large enough to respond well to very weak signals. Usually three feet up to ten feet is sufficient size for good DX response on MW.

The End-Fed Wire is generally any wire antenna that has no feed line - one end of the antenna connects directly to the receiver antenna input. Usually, EFW antennas are between 75 and 150 feet in length due to physical limitations of the user's property size. Since it's unavoidable that some of the antenna is going to be inside the house, noise levels on EFW antenna are generally high.

Below 500kc, most EFW antennas are going to be "short" and exhibit none of the advantages of typical "long wires" used on HF. However, long (that is, a few hundred feet long or more) EFW antennas do provide better signal to noise performance than the typical short EFW and in some quiet locations might out-perform a tuned loop that's used in a poor location. Extremely long, "Beverage antennas*" perform entirely different (much better) than the typical, short (for LW) End Fed Wire. The EFW's advantage is ease of installation and, even if the antenna is not tuned, it will still give a fairly consistent response throughout the receiver's tuning range. However, because of this wide response and lack of a feed line, it's susceptible to all kinds of noise - made man and atmospheric.

While it's interesting to compare the two antennas, I have found that almost without exception a well-designed, fairly large, tuned loop antenna will always seem to outperform almost any end-fed wire when comparing signal to noise ratio (not necessarily signal strength.) This is especially true with more modern receivers - the newer the receiver's design, the better it usually works with a tuned loop antenna. Very early three-circuit tuner regenerative receivers (1920s) seem to be much happier with long wire antennas of various configurations rather than the relatively small tuned loop antennas. However when using WWII or later vintage receivers, either regenerative or superhet, generally the tuned loop antenna provides the low signal to noise ratio necessary for successful DX NDB station copy.

Be sure to read the next section, "270ft Long Center-Fed Wire Antenna," as this provides an example of what a sizeable wire antenna can do on LW in a RFI-quiet area.

*The Beverage antenna (developed by Harold H. Beverage of RCA) is a one to two wavelength long antenna that is terminated to ground on its far end with a 450 ohms non-inductive load resistor. The Beverage antenna is mounted fairly close to the ground with 3 meters specified, although not too much difference in performance is noted with heights from 6 to 15 feet above the ground. Any higher and the antenna will begin to pick up noise. Beverage antennas are directional off of the terminated end. If the 450 ohm resistor is removed the antenna will become bi-directional off of the ends. Beverage developed the antenna for low noise reception and competitive performance. Two wavelengths is the specified maximum length according to Harold Beverage.


270 ft. Long Center-Fed Wire Antenna

Last year (2016,) I put up a wire antenna that was primarily for 75 meter operation. I wanted to run "two half-waves in-phase" which is basically a 160M dipole antenna operating on 75M. I used 135 feet of wire on each side and fed the center with 77 feet of 450 ohm ladder line. The ends were supported by a counterweight and pulley system erected in some cottonwood trees. Most of the antenna was about 30 feet off the ground but to the south-east the height was up about 37 feet. The center support was 31 feet high. The entire antenna was matched to the transmitter using a Nye-Viking antenna coupler. This system worked great on 75M. I noticed that received signals were generally 20db stronger than with the previous wire antenna (135' Inv-Vee.)

I hadn't thought about using this 270' antenna on longwave until I started restoring a couple of low frequency receivers. The first LF receiver operational was a RBA-1. Since the only sizable antenna available was the 270' dipole, I connected this to the RBA-1. I disconnected the feed line from the Nye-Viking coupler and used a test lead to short the two ladder line wires together. This was then connected to the RBA-1 using a 14 gauge stranded hook-up wire going to the center conductor of the Navy coax fitting (antenna input.)

During the next few days, while I was repairing and aligning the RBA-1, I would test the results using this antenna system. I was completely surprised when I started receiving NDBs from Idaho during the day. The big surprise was the next afternoon (13:30) when I tuned in DC 326kc from Princeton, British Columbia. Finally, when I had the RBA-1 finished I ready to do a serious test the following morning. From 05:55 to 06:35 in the morning I tuned in 47 NDBs in about 40 minutes and five of those NDBs were newly heard ones (#305 to #309 for the total tuned NDBs.) Greatest DX was POA in Hawaii and DB in Burwash Landing in the Yukon. Almost all signals were quite strong and nearly all stations had one or two other NDBs on the same frequency. Another surprise was receiving the first ham signal I'd ever heard below 500kc. WH2XVN in Burbank, CA on 183kc.

To determine if this performance is a result of the antenna or the receiver will require another test. This time using the National RBL-5 receiver.

This antenna forms a "T" which might be considered a vertical with a large top hat. This is the typical antenna used at many NDB sites. Most antennas from the early radio days had a two to three wire horizontal separated with spreaders on each end. Then the center of the "flat top" was tied together and fed with a single wire dropping down to the radio building.

More testing is necessary to determine if this antenna configuration will continue to provide a relatively low-noise operation. Much of the RFI that plagues smaller outdoor antennae and even the tuned-loop (when used indoors) seems to be greatly reduced, especially in the 190kc to 300kc region. I also would like to check if the feed line is shorted at the feed point of the horizontal wires thus making the antenna a true "T" wire, if the performance remains unchanged.

This large wire antenna can be connected directly to a substantial earth ground when not in use. The counterweight system seems to keep the antenna stationary as the wind runs the weights up and down as the tree limbs move around.

More information will be added as I do more testing,...     November 5, 2017

UPDATE: While this antenna does provide strong signals, there's been only a few times that conditions are quite. Most noise is in the form of static and bursts. This could be wind noise or nearby storm fronts. With quiet conditions, this antenna is great but those conditions seem to be rare.  November 23, 2017           

Had great conditions on Dec 23, 2017, 44 stations copied in 40 minutes, one newly heard NBD in LaSalle, MB, CAN, LF-336kc, on the RBA-1 receiver. Best DX - FIS 332kc Key West, FL

The upshot here is,...when conditions are great this 270' x 77' "T" antenna is unbeatable. BUT, if anything does "beat" this antenna, it's noise,...not RFI but atmospheric noise. This is mostly caused by the ionosphere but it can also be weather-related.


Remotely Tuned Loop Antenna Design


photo above: The 6' loop (measured across the diagonal) uses a 3/4" pine board center piece to hold the four 3' long arms that are made of 1x2 redwood. The gray box contains the varactor diode board. The gray cable is the bias supply from the remote box at the receiver location. The black cable is RG-58U routing the pick-up loop signal to the receiver. Cables can be any reasonable length but since this loop is near the receiver, the cables are about 20' long. The loop has a base (not shown) to allow it to free-stand and be pointed in any direction. The "diamond" shape orientation seems to work better than the "square" mounting by providing slightly lower background noise and slightly stronger signals.

 My first tuned loop antenna was a ten foot in diameter octagon with 12 turns of 20 gauge stranded wire remotely tuned with variable bias supplied to MVAM-108 varactor tuning diodes. The bias control, or tuning, was located at the receiver position for ease of operation and the bias voltage ran to the antenna via RG-58U coax cable. Tuning range was from 135kHz to 400kHz and by shorting out a turn on the loop the upper end of the range was increased to 500kHz. A 9' diameter single turn pick-up loop was mounted inside the 10' loop and was fed directly to the receiver's antenna input via RG-58U coax. This antenna performed very well with WWII vintage regenerative TRF receivers. Though the 10' loop antenna provided great signals it had a couple of problems. First, due to its size it was non-directional. That might be considered an advantage since I didn't have to provide any method of changing where it pointed. Second, due to its size it had to be located outdoors where it was highly susceptible to strong wind damage. After repairing the wind-broken 10' loop several times, I decided to rebuild the loop into a smaller configuration. This would result in a stronger antenna and would also result in some directional characteristics.

The new loop is a square with four foot sides and six feet across the diagonal. 17 turns are used in the antenna portion of the loop. A separate pick-up loop couples the signal energy from the tuned antenna where it is then routed to the receiver. I initially tried a single turn pick-up loop but found the signals were too weak. This was probably because of the very low impedance of the single turn, its physical length only being about 16 feet. I ended up using a three turn pick-up loop and found this gave much better performance. The pick-up loop is fed with RG-58U and connects to the receiver in use. The loop itself is connected to a small plastic box that contains the varactor diode board, connectors and a switch that selects the tuning range. The loop is tuned by varying the bias voltage (0 to +9vdc) on the varactor diodes. The frequency range is from approximately 195kc up to 440kc in two tuning ranges. This loop antenna is very directional and strong stations that are perpendicular to the antenna axis can almost be nulled out. Since this loop is relatively small, I have it indoors in the same room as the receivers. This location has eliminated the wind damage issue. Rotation is manual and since the upstairs floor is wood, I can set the antenna on the floor with no noticeable losses. In operation, signals received on this indoor 6' loop with a three turn pick-up are just about as strong as the outdoor 10' loop was and since it is directional it has the added advantage of increased signal strength when pointed towards the signal source.

Loop Details: The spacing of the loop wires is not especially critical. About .25" seems to work fine. If the wires seem to get tangled, again, this doesn't really seem to affect antenna performance much. The combs that keep the wires separate are made of .25" thick oak and have sawn notches for the wire mounting. The combs are held in place at the arm's end with glue and screws. To achieve two tuning ranges, I use switched parallel varactor diode sets. The capacitance for a single set is about 30pf to 300pf and a parallel set is about 60pf to about 500pf. The switch is located at the antenna box which would be inconvenient if the antenna wasn't indoors. I use a 9vdc transistor battery as the bias voltage source and a ten turn, 10K pot with some limiting resistors to control the bias voltage to the varactor diode junctions.

Schematic for Loop Remote Tuning - Shown to the right is a schematic for a very simple way to remotely tune a loop antenna by using varactor diodes. As described in the section above, this circuit can be built into a weather-proof plastic box that can be mounted at the loop. RG-58U coax cable can be used to connect the box to the remote tuning box that will be mounted beside the receiver. A standard project box can be used for the remote tuning box. Battery voltage is provided with a nine-volt transistor battery and tuning is accomplished with a ten-turn potentiometer. The remote tuner is also mounted inside a box for ease of operation. An "ON-OFF" switch is provided to isolate the battery when the loop is not being used. The coax can be any reasonable length. The longest I've used is around 50 feet with no problems. You can use PL-259 connectors on the coax and SO-239 box connectors on the remote tuning box and the loop box. The resistors and the capacitor are not critical and only provide a filter for the bias supply to the varactor diodes. I used three turns on the pick-up loop as I found two turns didn't provide strong enough signals. Best results will depend on the antenna input Z of your receiver.

To increase the lower end of the tuning range it is possible to switch in a fixed 500pf silver mica capacitor in parallel with the loop terminals. This will reduce the overall tuning spread but will lower the frequency bottom end by about 40kc or so. As shown, the loop tunes 240kc up to 440kc. With a parallel cap switched in, the low frequency is 195kc. If the parallel cap is added a double switching arrangement can be used for better isolation. A higher value cap can be installed to lower the bottom end frequency more if desired but the variable tuning range will decrease as the frequency is decreased. A three position switch (with an off position, too) could be installed to allow a selection of 500pf, 1000pf and 1500pf fixed value capacitors to allow loop tuning to go down to about 150kc or so.

Additional Loop Antenna Information as of Jan. 29, 2009:   I'm very pleased with the performance of the six-foot loop. I really think its performance is at least equal to the ten foot loop that was mounted outside and, many times, I think it's actually better. During the past two months (12/08 and 1/09) I have logged over 100 new NDBs using the 6' loop. That's not total NDBs heard  - it's just new NDBs I hadn't heard before. Best DX was YY 340kc in Mont Joli, Quebec at around 2500 miles. Also, in the other direction, LLD 353kc at Lanai City, Hawaii - also around 2500 miles. Greatest DX wasn't a new NDB for me - it was DDP 391kc in San Juan, Puerto Rico at around 3500 miles - but DDP is a transatlantic beacon running 2KW - it's not hard to receive. I think the main advantage of the six-foot loop is the ability to point it in the direction of the stations and exclude other stations that are perpendicular to the antenna axis. LLD is a good example since Reno's NDB NO is very strong and transmitting on 351kc and LLD is on 353kc. LLD is a transpacific beacon running 1-2KW and would be an easy copy if NO was not a local NDB. Fortunately, those two NDB signal paths are physically about 90 degrees apart at my location so I can somewhat null NO and copy LLD by pointing the loop SW. Signal levels on the six-foot loop are about the same as the ten-foot loop was. The receiving limitations are primarily the atmospheric noise and relative conditions, then local noise and finally the receiver's ability to pull signals out of the noise. The RAZ-1 is very good at weak signal detection.

UPDATE - 2015:  I've used this loop antenna with many different LW receivers and it seems to work quite well with just about any receiver. When I acquired the Hammarlund SP-600VLF receiver I found that the loop acted differently with respect to the apparent Q of the loop with tuning seemingly so "broad" that it was difficult to find a "peak." I ended up removing one turn on the pick-up loop and with two turns, the loop "peak" could be tuned although it was still somewhat broad. The recommendation is that depending on your receiver input Z you may have to work with the length of the pick-up loop (number of turns) to determine optimum tuning response.

UPDATE - 2018:  I've been having trouble with the loop working well with two receivers. The SP-600VLF seemed to make the loop very broad tuning with difficulty finding a "peak." I removed one turn on the loop which helped a little. Then with the R-389, I didn't seem to have enough signal strength from the loop. To try to "fix" the two problems, I've now increased the number of turns on the pick-up loop to four to increase gain. In order to increase selectivity, I've reduced coupling by reducing the size of the pick-up loop. It had been spaced about 1.5" inside the primary loop. I've doubled the distance so now the pick-up loop is 3" inside the primary loop. I'm hoping that the four turns results in strong signals and the greater distance will make the loop "tune" sharper. In a quick test I tuned the R-389 to the nearby DGPS 314kc node as a test signal during mid-day. The loop peak tuning showed 25db on the carrier level meter. As a reference, the 135'x100' "T" outdoor wire antenna showed 40db. The tuning Q didn't change too much but with the R-389 the peak is easy to find. Further testing will reveal if this change benefits DX reception for both the R-389 and the SP-600VLF. November 5, 2018 using the SP-600VLF and the loop I was able to copy NO3M on 473kc. His QTH is Pennsylvania. I'd say the loop works fine with the SP-600VLF. However, the R-389 still favors a wire antenna.

Adding the HP 461A Broadband Amplifier to the Remotely-Tuned Loop

Several years ago, N7ID loaned me a Hewlett-Packard 461A Broadband Amplifier to use with the RAK-7 receiver I was then using for longwave. I installed the 461A between a wire antenna and the receiver. All I got was a tremendous increase in noise and not much, if any, signal gain. I returned the 461A and didn't think about that type of amp again. A few years later I had tried a homebrew solid-state amplifier on my six foot remotely tuned loop but its performance was terrible. It seemed to have so much gain that I'd tune in the AM BC band stations along with various NDBs. Recently, I began thinking about the HP 461A again. When I had used it before, it was an untuned input coming from a random length wire antenna. If I installed the 461A with the loop's pick-up loop as the input that would add the tuned frequency input ability of the main loop along with the pick-up loop's selectivity. This would tend to reduce the amount of noise while enhancing a specific tuned frequency. The output of the 461A would be connected to the antenna input of the receiver.

HP-461A Specs - These small solid state amplifiers had a built in power supply and had selectable fixed gains of either 20db or 40db. Input and Output impedance is 50Z ohms. Frequency bandwidth is 1Khz up to 150Mhz. The input voltage limit is 2vdc and 1vac.

Performance - For the first test I used the Collins R-389 and a 160' End-Fed Wire. This is about as noisy of an antenna that can be found. With the 461A connected between the EFW and the receiver all that seemed to be increased was noise. Signals that were audible disappeared into the noise with 20db of amplification. Next, I substituted the loop antenna and tuned in the DGPS node on 314kc. It was pretty strong with no amplification and very strong with 20db but with 40db of amplification the input overloaded the receiver and the signal seemed to disappear. Returning to 20db and then the 314kc node was again present. At 2230 hours I tuned in NDB MOG 402kc. I showed about 20db on the carrier level meter (a strong signal) without the 461A on. With 20db of amplification, as one would expect, the meter read 40db. But, if 40db of amplification was selected, then the signal disappeared because the input was so strong that it "blocked" the receiver front end.

Now, that was the 461A performance receiving fairly strong signals. What about really weak signals? Here's where receiving conditions really matter. It's a fine line between the loop + amp responding mainly to noise or responding to a weak signal that is just above the noise. Several times, I would tune in a signal that could be heard without the 461A connected but when the 461A was added, even with just 20db selected, the weak signal would just disappear although the noise had a major increase. Since all DX LW signals are weak and basically just slightly above the noise, it seems like the 461A usefulness will be nil. >>>

>>> This testing was performed at the end of August, so LW conditions weren't very good and there was quite a bit of noise on the band. I'll update this performance section when I do further testing when conditions will be much quieter.    August 2018

UPDATE: Oct 1, 2018 - I tried the HP-461A with the modified loop antenna this morning. The pick-up loop turns have been increased to four turns and the coupling has been reduced by moving the distance between the tuned loop and the pick-up loop to 4.5." As noticed before, it's a fine line between adjusting for a weak signal increase or just amplifying the noise. Conditions weren't great but still a lot of DX NDBs were being received on the "T" wire antenna. The loop without the 461A was about 15db below what the wire would receive. With the 461A inline I had tuned in ZP 367kc in Sandspit, Queen Charlotte Islands. BC. By reducing the RF gain down slowly, a "sweet spot" could be found where the noise was low and the signal in the clear. Without the 461A, using just the loop, ZP was not received. However, when connecting up the "T" antenna, ZP was extremely loud and significantly above the noise. The 461A can provide an advantage in some conditions. As with any Long Wave listening, at different times, different antennas or combinations will seem to perform better than others. 


Headphones versus Loudspeaker

The final necessity for successful reception of weak LW signals is using the proper audio output reproducer. If you use a loudspeaker you can just about eliminate 70% of the NBDs that you would probably hear if you used headphones. Nearly all of the DX NDB signals are weak in signal strength. Most signals are in the noise. Much of the time you are trying to copy the weakest NDB that's on the same frequency as a couple of strong NDBs. Listening with a set of 'phones enhances your perception when copying weak signals that are buried in QRM and QRN.

Most vintage military LW radio receivers provide a 600Z ohm audio output. Finding a set of 600Z ohm 'phones is pretty easy. If you are looking at the WWII military headsets that provide a short cable with a small phone plug that then plugs into a six-foot extension cable, then you look at the color of the small phone plug shell. If it's red then it's Low-Z or 600Z ohms, if the shell is black then the 'phones are Hi-Z or around 10K Z ohms. This color code only applies to WWII 'phones. Later, in the 1950s, 600Z 'phones were considered Hi-Z, so these types should be measured to verify actual impedance.

Most early vintage LW receivers have high impedance outputs that might have the 'phones connected directly between B+ and the audio output tube plate. You must use Hi-Z 'phones for this type of receiver. Generally the older style 'phones work fine, especially those from the 1920s that were designed for direct B+ to plate connection.  >>>

>>>   If the headset is not marked then measure the DCR at the connecting plug or the phone tips to determine the probable impedance. Hi-Z phones will measure above 1K ohms DCR while 600Z ohm phones will measure around 100 ohms DCR. If you measure a very low DCR (< 5 ohms) then the impedance is 4 or 8 ohms. This test is an approximation to estimate probable impedance. Remember, 'phone impedance is "nominal impedance" and dependent on what frequency is used in the calculation. Generally, nominal impedance meant that the specified Z was the lowest Z that the would be encountered when the 'phones were used in a standard configuration listening to average signals at average levels. Pretty vague, don't take the specified Z as something that is ultra-critical,...close is okay. 

Once you have your 600Z ohm 'phones, check the schematic on your particular LW receiver to see how the audio output is designed. Most military LW receivers were designed for "headphones only" use and the 600Z ohm audio output is at the phone jack on the front panel (usually.) Later LW receivers might have the phone jack connect to the 1st AF stage or the second detector (on a superhet) and it might be that the phone jack might have circuitry added to assure that the headset is not "over-driven." Best results will be obtained by connecting the 600Z ohm 'phones to the "actual" 600Z ohm audio output stage. This may or may not be "at the phone jack" so check your receiver's schematic and connect your 'phones to the "actual 600Z ohm audio output." You'll have to be careful and only use enough gain to hear the average noise level in the receiver output. Even then, sometimes "pops" and "clicks" can get thru the Noise Limiter and "over-drive" your ear drums. Keep the 'phone cups just slightly in front of your ears to avoid problems.

Using a good set of headphones will enhance your listening and your DX NDB log.



US Coast Guard - Loran C Master Station 'M'
  100 kHz - Fallon, Nevada


NOTE:  As of February 8, 2010 the Loran-C system will begin its permanent shut down


On February 8, 2010, I tuned in Loran-C Master Station 'M' at 8:30AM PST and it was operating as usual. Tuning in later in the afternoon, at 5:15PM PST, Master Station 'M' had ceased operating. In August 2010, it was noted that Station 'G,' the last remaining West Coast Loran signal, was not transmitting.


Consider all Loran-C operations "OFF THE AIR"


Fortunately, we toured Master Station "M" in July, 2007 and were able to take several photos of the station including the Megapulse Transmitter and the Control Room - photos and description below...



photo right: Loran C  Station Fallon "Master of the Pacific Since 1977"  Arm Patch

Above: The Loran C antenna from main gate. The mast is 625 feet tall with each side measuring about six feet across. The capacity hat is about 900 feet diameter and is formed by the 24 top cables drooping down to large isolators. The size of the installation can be compared to the street lamps near the base of the antenna and just visible is the roof of the station house.

Just outside of Fallon, Nevada is the U.S. Coast Guard Loran-C Station which provides a navigation utility for the Pacific Ocean and the West Coast. Loran-C is part of a world-wide system of navigation mostly used for sea going craft. The Fallon station is designated 'M' since it is the Master Control station for the other three West Coast stations designated 'Y' in Searchlight, Nevada, 'X' in Middletown, California and 'G' in George, Washington. These three stations along with the master station in Fallon allow navigators to determine their position by use of a special Loran C receiver that accurately measures the pulse characteristics of the received signal to determine station ID and then accurately measures the time delay of the precisely timed signal (based on a Cesium atomic clock standard) to determine the receiver's distance from the transmitter. By using the master station signal and at least one slave station signal, the receiver position is determined by timing the two wave fronts to determine their intersection point in reference to the receiver's location. If another slave station can be received then the calculation of intersection point becomes more accurate and likewise the receiver's position. Various corrections are incorporated into the computations to allow for skywave propagation (if any,) terrain (over land or over water) and other minute interferences. Three HP Cesium atomic clocks keep the accuracy of the system constant since correct timing to the nanosecond is essential for determining true position. The best accuracy of Loran C is about 50 to 150 feet.

The transmitter is running 400KW at 100 kHz. The antenna mast is 625 feet tall and 24 top conductors drooping down to large isolators form the enormous capacity hat for the system. The signal consists of a rapid, continuous "tick-tick tick..." centered at 100 kHz. The signal is actually a pulse train made up of eight pulses from each Loran C station. The Master 'M' station has an extra pulse in the train for identification as a "master." Timing is critical as every Loran C station is on 100 kHz and each station has to send its pulses at a precise time for the system to maintain accuracy.

The Fallon Loran C is easy to receive anywhere in the west. It is particularly strong in Virginia City as we have "line of sight" to the Loran-C antenna, even though it is nearly 60 miles away. This is because VC is on the east slope of Mt. Davidson at 6200 feet elevation and looking 60 miles east is Fallon at 3980 feet elevation. You can see Mt. Davidson from the Fallon Loran-C Station. The USGC station and antenna are located West of Fallon at the end of Soda Lake Rd. with a right turn onto Loran Rd. to the site.

Below are some photos taken at the station in July 2007.

Above: The Control Room with Signal Generators, three Cesium atomic clocks, signal and transmitter monitoring, alarms, communications with slave Loran stations. Everything has a duplicate for redundancy.

Above Left: The 625' Antenna base stands on five ceramic insulators. The entire weight of the tower and guy system is supported by these 5" diameter insulators. The feed line is an air spaced coaxial feedline housed in an eight-inch diameter PVC tube that exits from the transmitter building. The box at the end of the feedline is the lightning arrestor. The output of the feedline connects to the tower base with 2" diameter copper pipe. The device to the left of the tower is a coupling transformer for the tower lights - it allows isolation from the AC line if the tower is struck by lightning. The ground connection can be seen at the base of the insulators - four copper sheets 2 ft. wide and .125" thick are buried and also connect to the radial system that is about 900 feet diameter. For a scale to the size of this installation, the sides of the tower are 6 feet across. The circular pads at the top of the triangular section are for fitting spacers to hydraulically jack the entire tower up for maintenance to the base mount.

Left: The Loran C 400 KW transmitter built by Megapulse. Most of the transmitter consists of sixteen drivers (eight panels on each side) that shape the final output signal. The station can operate with up to two drivers not working. Past the drivers is the output stage followed by the output coupler. The output coupler attaches to the feedline via two large cables (this 8" PVC feedline exits the transmitter building wall and goes directly to the antenna.) The incredibly large switching load on the transmitter power supplies results in a very loud audible representation of the transmitted signal.

Right: Looking into the rear of the transmitter bay. The red tags remind the technicians that 30,000 volts is present when the transmitter is operating. Also note the yellow sign regarding the noise present around the transmitter.

Left:  The output coupler stage of the transmitter. One inductor is hand tuned for a "rough" setting while the final tune is accomplished remotely with the motor driven inductor. Below the inductors is the solid state output magnacoupler. Large capacitance can be used with solid state transmitters resulting in smaller inductors. These inductors are about 10" diameter. The coils are wound with a cloth covered multiconductor cable. Note the output cable routed thru the fiberglass wall. This is then routed up to the antenna to feedline coupler that can be seen in the photo above-right.

Right:  The output tank stage which is adjacent to the output coupler. The tuning inductance is adjusted with a special tool that fits onto the eccentric knob on the shaft. This allows adjustment with the panel installed and the transmitter operational. Below are the massive capacitors that allow the use of smaller inductors. For size reference, the inductor is about 10 inches diameter.

NOTE: These photos were taken of the standby units. The access doors to the operational units cannot be removed while the transmitter is running without causing a system shutdown. Even removing these standby unit access doors would have triggered an alarm had it not been bypassed in the Control Room prior to opening.

Thanks to USCG ET1 Chris Shanks for the tour of the facility. 


Non-Directional Beacon Stations

 NDBs in Nevada

Ah,...the good old days, when there were loads of NBDs everywhere,...even in Nevada. Today (2014,) there are no active NDBs in the state. Here's information and some photos of the last two NDBs in operation in Nevada. Both have gone "off the air" in the past few years - AEC 209kc (OTA 2009) and NO 351kc (OTA 2013.) Additionally, I've added information on some of the older NDBs that were operating here in Nevada in the past.

"NO" - 351 Khz - Reno, Nevada - NDB for Reno-Tahoe International Airport


Located on 351 KC is the NDB for Reno-Tahoe International Airport. "NO" runs 25 watts and is a marker beacon physically located at the north end of the airport, in an empty lot, across the street (Mill Street) from the beginning of runway 16R. The antenna is only about 15 feet of vertical radiator with a capacity hat that is about 15 feet off the ground and about 150 feet long. The capacity hat is strung between two "not very tall" telephone poles. The transmitter and climate control equipment are located in and around a small building below the center of the capacity hat. The feed actually enters on the west side of the building through an underground conduit. Coverage is quite good considering the low power of the transmitter and the small antenna. Since "NO" is a marker beacon, it usually isn't listed on any of the NAV-AID sites - but it is operating 24 hrs a day, on 351 KC. About once a year, "NO" is "off the air" for a period of 2-3 weeks. Whether this is due to failures or scheduled maintenance is not known - the signal always seems to return after a few weeks.


NO has been off the air for over three months now. This is the longest shutdown yet. Hopefully, NO will return to the air pretty soon. When in Reno last (end of Oct.2013) I drove over to Mill St. to look at the NO site. Everything is still there, the shack, the antenna. Everything appears normal but as of November 7, 2013, NO is still OTA.

No change as of July 1, 2014. Consider NO "Off The Air." See updated photo lower right.

NOTE:  As far as I can tell, "NO" was the last operational NBD in Nevada.

photo above:
Full view of the "NO" site from Mill Street looking North. Around 2007

photo above: Taken from the rear of an auto-repair dealership looking NE. John Ascuaga's "Sparks Nugget" towers are in the background. Note the short telephone pole on right side of photo. This was the antenna support (east side) and was only about 15 feet tall. The west pole was near the fence.   Around 2007

photo above: Close-up of the "NO" shack around 2007

photo above: I took this shot of the NO site on September 21, 2015. As can be seen, nothing is left of the NO radio shack, transmitting equipment, antenna or associated structures. The property has been totally cleared. Compare this shot to the shot directly above and it can be seen that the NO shack was located just about center of the view and slightly to the right of the Nugget Towers. I took this shot from the same location behind the auto-repair dealership on Mill St. This pretty much concludes that NO 351kc will not be returning to the air.





"AEC" - 209 kHz - NDB for Base Camp, Nevada

AEC is on 209 kc and can be received here day or night, indicating that the transmitter might be running power higher than the 25 watts normal for NDBs. AEC is located near Warm Springs, Nevada on Hwy 6 about 60 miles east of Tonopah, Nevada. The site is called Base Camp. The antenna is an "inverted L" configuration with the shack located at one end near the pole support. From aerial photos it appears that there are a number of ground radials running out from a central location between the two poles. At one time AEC transmitted voice weather along with the MCW ID, however nowadays just the CW ID is transmitted.  Base Camp is a US government controlled, fenced air field with a maintained runway and some minor support buildings. Though the runway was recently repaved, there are large "X"s painted at each end of the runway to indicate "as viewed from the air" that it is closed and not in use. Apparently no hangers are at the site. What the exact use of Base Camp is remains unknown, although once it was part of the Tonopah Test Range. Though some speculate it now has some connection with Groom Lake/Area 51, this is highly unlikely. AEC is not listed on any of the NAV-AID sites yet it is in operation 24 hours a day, everyday. It is listed on LF websites that show logs of received stations.


AEC 209kc has been Off the Air since Sept.2009

Consider AEC "OFF THE AIR"



photo left: AEC at Base Camp, NV - this great photo is by Steve McGreevy N6NKS, from

Other Nevada NDBs (Inactive)

EMC - 375kc - Winnemucca, NV - Off the air since 2002

MCY - 326kc - Mercury, Nevada was operated by the US Air Force & the DOE at Desert Rock. Location was north of Las Vegas, near Beatty. Listed on several NAV-AID sites. Latest online information suggests that the NDB is active and is located at the Beatty, NV Airport - info is dated Nov '08. MCY has not been received here and although it is on the same frequency as the powerful Canadian NDB DC, Princeton, BC, it should still be an easy copy. Consider MCY inactive.
PYD - 414kc - Groom Lake, Nevada (Area 51) Sometimes listed on NAV-AID sites but has been off the air for several years.

SPK - 251kc - Sparks, Nevada has been off the air for at least 25 years. The location was at the old Reno-Cannon Airport (now Reno-Tahoe Int'l AP.) This station had continuous voice weather along with MCW "SPK" ID.

XSD - 278kc - Tonopah Test Range - Inactive


NDB Station Log 2006 to 2019

From Virginia City, Nevada - 2006 to 2012 - A large percentage of the following NDB stations are ones that I copied from Virginia City, Nevada using only vintage, tube-type receivers. I used several different types of vintage LW receivers. Many NDBs were heard using the 1941 RAZ-1 receiver, but I have also copied quite a few with the 1945 RAK-7 and 1944 RBL-5 receivers. I also logged some "newly heard" NDBs during experiments when testing the 1920 SE-1420, the 1922 RMCA IP-501A and the 1940 Hammarlund SP-200-LX receivers. For the 2009-2010 season, I added the 1945 RBA-6 receiver. My first dedicated LW antenna was a 10' diameter remotely tuned loop but that was destroyed by wind. Now, the main LW antenna is a 6' remotely tuned loop located indoors (as of Nov'08.) I also found some new NDBs using various wire antennas. These NDB stations were received during the 2006 to 2012 seasons. Stations are listed alphabetically along with frequency, location and power of the transmitter, if known. Total was 252 NDBs received from Virginia City 2006 up to 2012.

From Dayton, Nevada, the new QTH beginning in 2012  We are now in Dayton, Nevada (10 miles SE of Va.City.) For a short time (2013-14,) the antenna used was a 300 ft. long end fed wire up about 50 feet. New NBDs for 2012/13 and 2013/14 seasons are shown in Navy Blue. Receiver was the RBA-6. EFW antenna taken down Mar 2014. Six newly heard NDBs were logged with this combination. Total Spring 2014 was 258

2014-2015 Season - Nov. 2014, started using Hammarlund SP-600VLF-31 receiver. New NDBs heard with the SP-600VLF are in Maroon. Changed to 6' Remote-tuned Loop Nov.15, 2014.

2015-2016 Season - Started listening Oct. 2015, Hammarlund SP-600VLF-31 and 6' Remote-tuned Loop. Total newly heard NDBs logged (2015/16) with this combination is 35 - Maroon

2016-2017 Season - Hammarlund SP-600VLF-31 w/ 6' Remotely-tuned Loop - First new NDB this season on Nov.30, 2016 (AN-368kc.) Total new with this combo is 42  - Maroon

2017-2018 Season - Hammarlund SP-600VLF-31 w/ 6' Remotely-tuned Loop - First new NDB this season on Oct. 13, 2017 (DUT-283kc.) Total new with this combo is 61 - Maroon
        Nov 3, 2017 using RBA-1 with 270' CF dipole with 77' of ladder line with the two wires tied together and fed to antenna input. Newly heard with this set-up (6) will be in Orange.
        Jan 8, 2018 started using Collins R-389/URR with 135' "T" wire antenna. Newly heard with this set up (2) will be in Dark Green.

2018-2019 Season - Collins R-389/URR w/ 100' x 135' "T" Wire Antenna - First new NDB this season on Sept. 24, 2018 (ZZP-248kc) Total new with this combo is 15 - Dark Green

Total NDBs logged as of JAN 11, 2019 is 340

AA - 365kc - Fargo, ND - 100W

ADT - 365kc - Atwood, KS

AE - 351kc - Dudle-Albuquerque, NM

AEC - 209kc - Base Camp, NV - OTA

AFK - 347kc - Nebraska City, NE - 25W

AGZ - 392kc - Wagner, SD

AL - 353kc - Trina (Walla Walla,) WA

AM - 251kc - Amarillo, TX - 400W

AN -  368kc - San Antonio, TX

ANR - 245kc - Andrews, TX

AOP - 290kc -Rock Springs, WY - 100W

AP - 260kc - Denver, CO - 100W

AP - 378kc - Active Pass, BC, CAN

ATS - 414kc - Artesia, NM - 25W

AVQ - 245kc - Tucson, AZ

AZC - 403kc - Colorado City, AZ

BAJ - 392kc - Sterling, CO

BBD - 380kc - Brady, TX - 25W

BF - 362kc - Nolla-Seattle,WA

BI - 230kc - Jadan-Bismarck, ND

BK - 335kc - CHRLZ-Brookings, SD 25W

BKU - 344kc - Baker, MT - 80W

BO - 359kc - Boise, ID - 400W - OTA

BR - 233kc - Brandon, MB, CAN

BWR - 412kc - Alpine, TX - 25W

BY - 211kc - Beechy, SK, CAN

CBC - 415kc - Cayman Brac, Cayman Islands

CC - 335kc - Buchanan AF, CA - 25W

CEP- 278kc - Ruidoso, NM - 25W

CG - 227kc - Castlegar, BC, CAN

CH - 329kc - Ashly-Charleston, SC - 400W

CHD - 407kc - Chandler, AZ

CII - 269kc - Choteau, MT - 50W

CIN - 397kc - Carroll, IA - 25W

CKP - 423kc - Cherokee, IA - 25W

CL - 515kc - Port Angeles, WA

CLB - 216kc - Wilmington, NC - 1KW

CN - 235kc - Cochrane, ON, CAN 100W

CNP - 383kc - Chappell, NE - 25W

COR - 205kc - Corcoran, CA - 25W

CRK - 389kc - Spokane, WA

CRR - 245kc - Circle, MT - 100W

CRZ - 278kc - Corning, IA - 25W

CSB - 389kc - Cambridge, NE - 25W

CUH - 242kc - Cushing, OK - 25W

CVP - 335kc - Helena, MT - 150W

CY - 353kc - Cheyenne, WY

CYW - 362kc - Clay Center, KS - 25W

CZX - 332kc - Crosbyton, TX

DAO - 410kc - Ft. Huachuca, AZ

DB - 341kc - Burwash Landing,YK,CAN

DC - 326kc - Princeton, BC, CAN

DDP - 391kc - San Juan, PR - 2KW

DIW - 198kc - Dixon, NC - 2KW

DN - 225kc - Dauphin, MB, CAN

DPG - 284kc - Dugway Prov Gnds, UT

DPY - 365kc - Deer Park, WA - 25W

DQ - 394kc - Dawson Creek, BC, CAN

DUT - 283kc - Dutch Harbor, Amakrak Is., AK

DWL - 353kc - Gothenburg, NE - 25W

EC - 217kc - Cedar City, UT - 25W

EF - 206kc - Champion-Castlegar, BC, CAN

EHA - 377kc - Elkhart, KS - 25W

EHM - 385k -Cape Newenham,AK  100W

EKS - 286kc - Ennis, MT - 25W

EL - 242kc - El Paso, TX - 400W

ELF - 341kc - Cold Bay, AK - 1KW

ENS - 400kc - Ensenada, Mexico

ENZ - 394kc - Nogales, AZ - 100W

ESY - 338kc - West Yellowstone, MT - 100W

EUR - 392kc - Eureka, MT - 100W

EX - 374kc - Kelowna, BC, CAN

FCH - 344kc - Fresno, CA - 400W - OTA

FIS - 332kc - Key West, FL

FMZ - 392kc - Fairmont, NE - 25W

FN - 400kc - Ft. Collins, CO

FO - 250kc - Flin Flon, MB, CAN

FOR - 236kc - Forsyth, MT - 25W

FQ - 420kc - Fremont, MN - 25W

FS - 245kc - Sioux Falls, SD - 100W

FS - 375kc - Ft. Simpson, NWT, CAN

GB - 253kc - 'Garno' - Marshall, MN

GC - 380kc - Gillette, WY

GDV - 410kc - Glendive, MT - 100W

GEY - 275kc - Greybull, WY

GGF - 359kc - Grant, NE

GLS - 206kc - Galveston,TX-2KW - OTA

GLY - 388kc - Golden Valley-Clinton, MO


GNC - 344kc - Seminole, TX - 25W

GRN - 382kc - Guerrero Negro, Mexico

GRN - 414kc - Gordon, NE

GUY - 275kc - Guymon, OK - 25W

GW - 371kc - Kuujjuarapik, QC, CAN

GYZ - 280kc - Guernsey, WY - 50W

HAU - 386kc - Helena, MT

HBT - 390kc - Sand Point, AK

HCY - 257kc - Cowley, WY

HDG - 211kc - Gooding, ID - 50W

HE - 245kc - Hope, BC, CAN

HF - 241kc - Hearst, ON, CAN  100W

HIN - 275kc - Chadron, NE - 25W

HJH - 323kc - Hebron, NE - 25W

HLE - 220kc - Hailey, ID - 50W

HQG - 365kc - Hugoton, KS - 25W

HRU - 407kc - Herington, KS - 25W

HRX - 341kc - Hereford, TX

IB - 209kc - Atikokan, ON, CAN

ICL - 353kc - Clarinda, IA - 25W

ID - 324kc - Idaho Falls, ID

IKY - 429kc - Springfield, KY - 25W

ILT - 247kc - Albuquerque,NM - 400W

IN - 353kc - International Falls, MN

INE - 521kc - Missoula, MT - 400W

IOM - 363kc - McCall, ID - 25W

IP - 201kc - Mobile, AZ

ITU - 371kc - Great Falls, MT - 100W

IY - 417kc - Charles City, IA - 25W

JDM - 408kc - Colby, KS - 25W

JHN - 341kc - Johnson, KS

JM - 396kc - Jamestown, ND

JW - 388kc - Pigeon Lake, AB, CAN

K2 - 376kc - Olds-Didsbury, AB, CAN

LAC - 328kc - Ft. Lewis, WA - 25W

LBH - 332kc - Portland, OR - 150W

LD - 272kc - Lubbock, TX

LF - 336 - LaSalle, MB, CAN  50W

LFA - 347kc - Klamath Falls, OR

LGD - 296kc - LaGrande, OR - 25W

LLD - 353kc - Lanai City, HI - 2KW

LLN - 266kc - Levelland, TX

LU - 213kc - Abbotsford, BC, CAN

LV - 374kc - Livermore,CA - 25W

LW - 257kc - Kelowna, BC, CAN

LWG - 225kc - Corvallis, OR

LWT - 353kc - Lewiston, MT - 400W

LYI - 414kc - Libby, MT - 25W

LYQ - 529kc - Manchester, TN

L7 - 395kc - Estevan, SK, CAN

MA - 326kc - Midland,TX - 400W

MA - 365kc - Mayo, YK, CAN

MDS - 400kc - Madison, IA - 25W

MEF - 356kc - Medford, OR

MF - 373kc - Rogue Valley, OR

MKR - 339kc - Glascow, MT - 50W

ML - 392kc - Charlevoix, QC, CAN

MLK - 272kc - Malta, MT - 25W

MM - 388kc - Fort McMurray,AB,CAN

MNC - 348kc - Shelton, WA

MNZ - 251kc - Hamilton, TX - 25W

MO - 367kc - Modesto, CA

MOG - 404kc - Montegue, CA - 100W

MR - 385kc - Monterey, CA

MW - 408kc - Moses Lake, WA

NA - 337kc - Orange County AP, CA

NM - 278kc - Matagami, QC, CAN

NO - 351kc - Reno, NV - 25W - OTA

NY - 350kc - Enderby, BC, CAN

ODX - 355kc - Ord, NE - 25W

OEG - 413kc - Yuma Prov. Gnds., AZ

OEL - 381kc - Oakley, KS - 25W

OIN - 341kc - Oberlin, KS - 25W

OJ - 239kc - High Level, AB, CAN

OKS - 233kc - Oshkosh, NE - 25W

OLF - 404kc - Wolf Point. MT - 100W

ON - 350kc - Newport, OR

ON - 356kc - Penticton, BC, CAN

ONO - 305kc - Ontario, OR

ORC - 521kc - Orange City, IA - 25W

OT - 378kc - Bend, OR

OUN - 260kc - Norman, OK - 25W

OWU - 329kc - Woodward, OK

PA - 396kc - Snohomish/Ritts, WA

PA - 347kc - Prince Albert, SK, CAN




PBT - 338kc - Red Bluff, CA -400W OTA

PBY - 259kc - Kayenta, AZ

PD - 230kc - Pendelton, OR - 400W

PDG - 327kc - Watsonville, CA - 25W

PG - 353kc - Portage, MB, CAN

PI - 383kc - Tyhee, ID

PN - 360kc - Port Menier, QC, CAN

PNA - 392kc - Pinedale, WY - 25W

PND - 356kc - Portland, OR

POA - 332kc - Pohoa-Hilo, HI

POH - 428kc - Pocahontas, IA - 25W

POY - 344kc - Powell, WY

PPA - 450kc-Puerto Plata, Dominican Republic

PRZ - 407kc - Portales, NM - 25W

PTT - 356kc - Pratt, KS - 25W

PY - 207kc - Ft. Chipewyan, AB, CAN

PYX - 266kc - Perryton, TX - 25W

QD - 284kc - The Pas, MB, CAN

QL - 248kc - Lethbridge, AB, CAN

QN - 233kc - Nakina, ON, CAN

QQ - 400kc - Comox, Van.Is., BC

QR - 290kc - Rigina Int'l, SK, CAN

QT - 332kc - Thunder Bay, ON, CAN

QU - 221kc - Grand Prairie, AB, CAN

QV - 385kc - Yorkton, SK, CAN

QW - 302kc - North Battleford, SK, CAN

RA - 254kc - Rapid City, SD - 100W

RD - 367kc - Redding Muni, CA - 25W

RD - 411kc - Redmond, OR - 400W

RG - 350kc-Will Rogers World AP, OKC,OK

RL - 218kc - Red Lake, ON, CAN

RMD - 204kc - McDermitt, OR - 25W

RNT - 353kc - Renton, WA - 25W

RPB - 414kc - Belleville, KS

RPX - 362kc - Roundup, MT - 25W

RWE - 528kc - Camp Roberts, CA

RWO - 394kc - Kodiak, AK - Voice WX

RYN - 338kc - Tuscon, AZ - 400W

SA - 356kc - Sacramento,CA

SAA - 266kc - Saratoga, WY - 25W

SAK - 515kc - Kalispell, MT - 25W

SB - 397kc - San Bernadino,CA

SB - 362kc - Sudbury, ON, CAN

SBX - 347kc - Shelby, MT - 25W

SC - 271kc - Stockton,CA

SCO - 283kc - Scobey, MT

SDA - 411kc - Shenandoah, IA - 25W

SDY - 359kc - Sidney, MT - 25W

SF - 379kc-San Francisco Intn'l AP, CA

SG - 341kc - Santa Fe, NM

SIR - 368kc - Sinclair, WY

SKX - 414kc - Taos, NM - 25W

SL - 266kc - Salem, OR - OTA (now SLE)

SLB - 434kc - Storm Lake, IA - 25W

SLE - 266kc - McDerrmit AP, Salem, OR

SM - 230kc - Metre/Sacramento, CA

SM - 254kc - Fort Smith, NWT, CAN

SOW - 206kc - Show Low, AZ - 25W

SRL - 270kc - Santa Rosalia, MEX

STI - 333kc - Mt. Home, ID

SWT - 269kc - Seward, NE - 25W

SWU - 350kc - Idaho Falls, ID

SX - 367kc - Cranbrook, BC, CAN

SYF - 386kc - St. Francis, KS - 25W

SYW - 428kc - Greenville, TX - 25W

SZT - 264kc - Sandpoint, ID

TAD - 329kc - Trinidad, CO

TCY - 203kc - Tracy, CA

TF - 373kc - Pueblo, CO

TH - 244kc - Thompson, AB, CAN

TK - 392kc - Telkwa/Smithers, BC, CAN

TOR - 293kc - Torrington, WY

TQK - 256kc - Scott City, KS - 25W

TV - 299kc - Turner Valley, AB,CAN

TVY - 371kc - Tooele, UT - 25W

TW - 389kc - Twin Falls, ID

U6 - 360kc - Creston, BC, CAN

UAB - 200kc - Anahim Lake, BC,CAN

UK - 371kc - Kearn, CA

ULS - 395kc - Ulysses, KS - 25W

UNT - 312kc - Penticton, BC, CAN

UVA - 281kc - Uvalde, TX - 25W

VC - 317kc - LaRonge, SK, CAN

VG - 230kc - Vermillion, MB, CAN

VQ - 400kc - Alamosa, CO

VR - 266kc - Vancouver, BC, CAN

VT - 332kc - Buffalo Narrows, SK, CAN


WG - 248kc - Winnepeg, MA,CAN

WL - 385kc - Williams Lake, BC, CAN

XC - 242kc - Cranbrook, BC , CAN

XD - 266kc - Edmonton, AB, CAN

XE - 257kc - Saskatoon, SK, CAN

XH - 332kc - Medicine Hat, AB, CAN

XJ - 326kc - Fort Saint John, BC, CAN

XS - 272kc - Prince George, BC, CAN

XT - 332kc - Terrace, BC, CAN

XX - 344kc - Abbotsford, BC, CAN

YAG - 376kc - Fort Frances, ON, CAN

YAT - 260kc - Attawapiskat, ON, CAN

YAZ - 359kc - Tofino,Van.Is., BC, CAN

YBE - 379kc - Uranium City, SK, CAN

YBL - 203kc - Campbell River, BC, CAN

YBV - 370kc - Berens River AP, MB, CAN

YC - 244kc - Cranbrook, BC, CAN

YCD-251kc - Nanaimo, Van. Is, BC, CAN

YCO - 375kc - Kugluktuk, Nanuvat, CAN

YD - 230kc - Smithers, BC, CAN

YE - 382kc - Fort Nelson, BC, CAN

YEL - 276kc - Elliot Lake, ON, CAN

YHD - 413kc - Dryden, ON, CAN

YHN - 329kc - Hornepagne, ON, CAN

YIV - 300kc - Island Lake, MB, CAN

YJ - 200kc - Victoria Island, BC, CAN

YJQ - 325kc - Bella Bella, BC, CAN

YK - 371kc - Yakima, WA

YK - 269kc - Castlegar, BC, CAN

YKA - 223kc - Kamloops, BC, CAN

YKQ - 351kc - Waskaganish, QC, CAN

YL - 395kc - Lynn Lake, MB, CAN

YLB - 272kc - Lac la Biche, AB, CAN

YLD - 335kc - Chapleau, ON, CAN

YLJ - 405kc - Meadow Lake, SK, CAN

YLL - 241kc - Lloydminster, AB, CAN

YMW - 366kc - Maniwaki, QC, CAN

YPH - 396kc - Inukjuak, QC, CAN

YPL - 382kc - Pickle Lake, ON, CAN

YPM - 274kc - Pikangikum, ON, CAN

YPO - 401kc - Peawanuck, ON, CAN

YPW - 382kc - Powell River, BC, CAN

YQ - 305kc - Churchill/Eastern Creek, MB, CAN - 500W

YQA - 272kc - Muskoka, ON, CAN

YQF - 320kc - Red Deer, AB, CAN

YQK - 326kc - Kenora, ON, CAN

YQZ - 359kc - Quesnel, BC,CAN

YSQ - 260kc - Atlin, BC, CAN

YTL - 328kc - Big Trout Lake, ON, CAN

YWB - 389kc - West Bank, BC, CAN

YWP - 355kc - Webequie, ON, CAN

YXL - 346kc - Sioux Lookout, ON, CAN

YXR - 257kc - Earlton, ON, CAN  400W

YY - 340kc - Mont Joli, QC, CAN

YYF - 290kc - Penticton, BC, CAN

YYU - 341kc - Kapuskasing, ON, CAN

YYW - 223kc - Armstrong, ON, CAN

YZA - 236kc - Ashcroft, BC,CAN

YZE - 245kc - Gore Bay, ON, CAN

YZH - 343kc - Slave Lake, AB, CAN

ZAB - 214kc - Leduc/Edmonton IAP, AB, CAN

ZEG - 379kc - Edmonton, AB, CAN

ZF - 356kc - Yellowknife, NWT, CAN

ZHD - 399kc - "Thunder" Dryden, ON, CAN

ZKI - 203kc - Kitimet, BC, CAN

ZQ - 410kc - Sir Wilfred Laurier CCGS*, BC, CAN

ZP - 368kc - Sandspit, Queen Charlott Is, BC, CAN

ZRG - 414kc - Regina, SK, CAN

ZSJ - 258kc - Sandy Lake, ON, CAN

ZSS - 397kc - Yellowhead-Saskatoon, SK, CAN

ZT - 242kc - Port Hardy, BC, CAN

ZU - 338kc - Whitecourt, BC, CAN

ZVR- 369kc - Vancouver (Sea Is.,) BC, CAN

ZXE - 356kc - Saskatoon, SK, CAN

ZYC - 254kc - Calgary, AB, CAN

ZZD - 308kc - Calmar/Edmonton Int'l AP, AB, CAN

ZZP - 248kc - Sandspit, Queen Charlotte Is, BC, CAN

Z5 - 274kc - Vulcan, AB, CAN

Z7 - 408kc - Claresholm, AB, CAN

3Z - 388kc - Taber, AB, CAN

6T - 362kc - Foremost, AB, CAN

9Y - 311kc - Pincher Creek, AB, CAN - 50W

Weird Beacons Copied Multiple Times**

INUU - 395kc - 11/2017 (also in 2016, 2019)

EEGU - 378kc - "Key Down" - 11/2017

OTA - Off The Air, Decommissioned

* Canadian Coast Guard Ship - Sea Mobile NDB

** not counted in total received

Henry Rogers WA7YBS © November 2007, new info added Oct.2008, Nov. 2008, Jan 2009, Nov 2009, updates Sept 2014, updates Jan 2015, update on "NO" 351kc with photo Sept 2015, updates on LW BC, 600M ham, RBA-1 rcvr Oct 2017, info on DGPS, GWEN, FCC Experimental License Grants, Nov 2017, added R-389 info Jan 2018,



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Western Historic Radio Museum Information
 Contact Info, Museum History 1994-2012, Museum Photo Tour, Using Photos and Info from this Website & Radio Value Info

Nevada Radio History - 1906 to 1930
Arthur Raycraft, Nevada's "Father of Wireless," America's First Radio Tour, Early Nevada BC Stations & More

KOWL's Gates BC-250L BC Transmitter
2007 Move from Lake Tahoe - Restoration - PLUS -  2013 Move to Dayton, Nevada & Getting on 160M

Parish House History
1876 to Present
Virginia City, Nevada

Lots of Photos


- Wireless Apparatus, 1920s Radio and Communications Equipment  ~  Full Length Articles with Photos -

M.H. Dodd's 1912 Wireless Station
100th Anniversary  Edition 
Includes New Photos, Reassembly Info and Lots of Original Vintage 1912 B&W Photos + Reassembly in Dayton

Universal, Intermediate Wave and Short Wave Models History, Restoration and Operation - Lots of Photos

"A Guide to the Synchrophase MU-1"
Comprehensive Manufacturing History, Restoration, Neutralizing, Performance Information - Lots of Photos


 SE-1420, IP-501 & IP-501A
"The Classic Shipboard Wireless Receivers"
Comprehensive History, Restoration and Operation Info - Tuning in NDBs with IP-501-A

Vintage Long Wave Receivers
Long Wave Receiver Profiles, Loop Antenna Info, NDB Info and Log,
Fallon NV "Master - M" Loran Station Tour



- Vintage Communications & Amateur Radio Equipment  ~  Full Length Articles with Photos -

National Co. - HRO Receiver
"The Cream of the Crop" 
Comprehensive History, Serial Numbers, Restoration, Lots of Photos & More

National Co. - NC-100 Series
"Moving Coil"  Receivers 
Comprehensive History, Serial Numbers, Restoration & More - Includes Civilian Versions, Military Versions & Airport Versions

Hallicrafters SX-28
"A Pre-war Masterpiece"

Comprehensive History, Serial Number Analysis, Restoration Details & More

Hallicrafters DD-1 "Skyrider Diversity"
Comprehensive History, Serial Numbers & Restoration Details

NEW!          Navy Dept - RCA - RAA-3 Receiver
1930s Ship or Shore Station Longwave Superheterodyne
History, Circuit Design & Construction Details,
Restoration Log with Lot of Photos

 RCA's Amazing AR-88 Receivers
Comprehensive History, Restoration Info, How to do IF Sweep Alignments, Serial Numbers & More

RCA's Legendary AR-60 Receiver
Comprehensive History, Serial Number Analysis, Restoration Details & More - including the AR-60 connection to Amelia Earhart's Disappearance

Hammarlund Mfg.Co.,Inc
The Incredible Pre-War 'Super-Pro'
Comprehensive History, Serial Number Analysis, Restoration Details. Includes info on the Hammarlund Comet Pro

Patterson Radio Company
   PR-10 Receiver & Pre-selector              
Comprehensive History, Los Angeles Radio Mfgs History, Circuit Details, Serial Numbers, Restoration Details & More

NEW!    Hallicrafters' Super-Pro, the R-274 Receiver
Comprehensive History, Circuit details with Comparison to the Hammarlund SP-600, Restoration Details, Best features of each Receiver. Yes! You can VOTE for your favorite Super Pro


-  Rebuilding Communications Equipment  ~  Full Length Articles with Photos -

Rebuilding the R-390A Receiver
Detailed Restoration Information for each module with Lots of Photos

Rebuilding the ART-13 Transmitter
Detailed Restoration info - includes details on building AC power supplies (with schematics) Lots of Photos

Rebuilding the Hammarlund SP-600
Detailed Restoration Information with Lots of Photos

           T-368 Military Transmitter                    
Detailed Information on Reworking, Testing and
Operation with Lots of Photos

Rebuilding and Operating the AN/GRC-19
T-195 XMTR & R-392 RCVR

 Detailed Information with Lots of Photos

Successfully Operating the BC-375 on the Ham Bands Today
Detailed Information on Power Set-ups that Work, Dynamic Neutralization, BC-191 Info & More

Rebuilding the Collins 51J Series Receivers
Detailed Restoration Information with Lots of Photos - Includes R-388 Receiver

Rebuilding the BC-348 Receiver
Detailed Information on all BC-348 Types, Dynamotor Retrofit Information, AC Power Supply Enhancement - Lots of Photos

Building an Authentic 1937 Ham Station
Utah Radio Products - UAT-1 Transmitter


- WHRM Radio Photo Galleries with Text -

Entertainment Radios from 1922 to 1950

Roaring 20s Radios
1922 to 1929

Vintage Table Radios
1930 to 1950

Floor Model Radios (Consoles)
1929 to 1939

Only Zenith Radios
1930 to 1940

Communications Equipment from 1909 to 1959 - Commercial, Military & Amateur

 Early Ham & Commercial Wireless Gear
1909 to 1927

Classic Pre-WWII Ham Gear
1928 to 1941

WWII Communications Equipment
 U.S. Navy & U.S. Army Signal Corps  1941 to 1945

Commercial & Military
Communications Gear
1932-1941 & 1946-1967

Post-WWII Ham Gear
1946 to 1959

Vintage Broadcast Equipment, RTTY, Telegraph Keys & Vintage Test Equipment

Vintage Microphones
 & Vintage Broadcast Gear
1930 to 1950s

Radio Teletype - RTTY - with Real Machines
includes TTY Machines, Military TUs and Amateur TUs

Telegraph Keys - 1900 to 1955
"From Straight Keys to Bugs"
Hand Keys and Semi-Automatic Telegraph Keys

Vintage Test Equipment
1900 to 1970

Includes Tube Testers, Freq Meters, Wobulators and More


Radio Boulevard
Western Historic Radio Museum

 Vintage Radio Communication Equipment Rebuilding & Restoration Articles,

 Vintage Radio History and WHRM Radio Photo Galleries

1909 - 1959



This website created and maintained by: Henry Rogers - Radio Boulevard, Western Historic Radio Museum 1997/2019