Radio Boulevard
Western Historic Radio Museum


Vintage Longwave Receivers

~ In Depth Profiles of the Following Receivers ~

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

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

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

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

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

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

 ~  RBA-6, CFT-46300 - RCA-Federal Tele.&Radio Corp. - 1945  ~

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

~   SP-600VLF-31 - Hammarlund Mfg Co., Inc.- 1958  ~

Miscellaneous Other Receivers with MW and LF Coverage  ~

Using Vintage Longwave Receivers Today
Signals Below 500kc, Noise, Propagation & Remote Tunable Loop Antenna Plans
600 Meter Amateur Band Proposal,
Regens and TRFs vs Superhets on Longwave

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

NBD Stations in Nevada  &  NDB Station Log

by: Henry Rogers WA7YBS

SAQ - Grimeton, Sweden

Nowadays, SAQ is probably the best known Long Wave station since they periodically run the only operational Alexanderson Alternator in the world. The mechanical transmitter produces a 200KW 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 and once on Christmas Eve. It is a challenge to receive SAQ almost anywhere in the USA today. Receiving a radio signal (CW) on 17.2kc requires an excellent location, a substantial antenna and, of course, a first class receiver. For more information on SAQ, go to their website at

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


"Longwave" generally describes all of the frequencies below the AM BC band. These frequencies are officially designated as Medium Wave, Low Frequency and Very Low Frequency.


Vintage Longwave Receivers

In Depth Profiles of Classic Longwave Receivers
(in order by earliest to latest year of manufacture)


Radiomarine Corporation of America
(Wireless Specialty Apparatus)


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

Commercial Shipboard Receiver from 1923


"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 the norm 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 and most difficult was probably ULS 395kc, a 25W marker beacon located in Ulysses, Kansas. Impressive performance from a 1922 regenerative receiver. In a three week period during the winter, I logged over 100 NDBs using just the IP-501-A. Some of the difficult NDBs received were PN 360kc Port Menier, Anticosti Island, Quebec, YY 340kc Mont Joli, Quebec, YKQ 351kc Waskaganish, Quebec and IY 417kc, a 25W marker beacon in Charles City, Iowa.

A history of these early wireless receivers and the companies involved is included in our article "SE-1420, IP-501 & IP-501-A - The Classic Shipboard Wireless Receivers"  - also included is an updated NDB log for the IP-501A that shows the incredible performance that can be achieved with early regenerative receivers - use navigation index at the bottom of this page.


Mackay Radio & Telegraph Company


  MW, LF & VLF Radio Receiver  Type 105-A

Serial No. 32081

Commercial Shipboard Receiver from 1932


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


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

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 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


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.


RCA-Andrea Radio Co.



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

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

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

The Navy wanted more modern LW, MW and SW receivers in the mid-thirties so RCA provided the Navy with the RAK/RAL series. Initially, the designation for the RAL was TBR. 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. Any receiver built of 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. The RAK/RAL series was just that - 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 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.

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. The tubes used 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.

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, the RAK might be considered a very large, heavy receiver with a separate large, heavy power supply - both units built like battleships - be sure to provide an ample table for the receiver set-up. In my installation I have 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 do run the power supplies with their ballasts even though it is probably not necessary. The actual difference in power consumption is significant - the ballast dissipates about 140 watts. I have run the receivers both with and without ballasts and I notice that the received noise seems to be 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 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 okay 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 and so are not very useful. Due to the RAK's high sensitivity, noise levels can get out of hand rather quickly. The tuned loop antenna, with its high Q, really helps reduce the noise and increase the signal to noise ratio. Additionally, the Audio AVC can be used in severe conditions. The audio output is taken from the front phone jack. It is 600 ohms Z 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 RTTY signals around 20kc are always present. Like many of the WWII Longwave receivers, once the RAK is used regularly and the operator becomes used to its quirks, it "becomes" a great performer - it was all along, the op just has to "learn" his receiver.

National Co., Inc.



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


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 built the RBL-3 and RBL-4 versions under contract.
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-46300, RBA-6 - MW, LF & VLF Radio Receiver - 1945

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. Another problem was that fact that the conversion process in a superheterodyne creates a lot of internal noise in the receiver - not a real problem on HF or SW, but a serious determent to good LF performance. Regenerative and TRF receivers with no conversion required are very quite receivers when it comes to internally generated noise.

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 sensitivity of the receiver but there is also a "tracking" gain control (also called the auxiliary gain control) that is geared to the main tuning. This allows a variable gain compensation to frequency tuned to allow 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 selectivity are provided, Broad selectivity rolls off the audio response at about 1300kc 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. The audio output is 600 ohms Z and is intended for earphones although the RBA will drive a matched loud speaker if necessary. 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. Early versions of the RBA receiver were identified as C(FT)-46154 (FT would indicate that Federal Tele. & Radio Corp. was the contractor) while the later versions are identified as CFT-46300.

 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.

This RBA-6 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.

I have been using the RBA 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.

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 - Shown in the photo to the left is the early version RBA, the CFT-46154. This particular RBA has had a common Field Change Contract installed which 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 (and for an RBA-1) while the panel has been repainted gray.

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

635kc to 15kc


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 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.


Hammarlund Manufacturing Company, Inc.




 MW, LF & VLF Superheterodyne Receiver

540kc to 10kc



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 1958 (component date code indicated.) 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 commercial or military users.

Comparison to the HF SP-600 - One notices the although the receiver is obviously a "600" it has several minor physical differences. One first sees grab handles on the front panel. Also, that the chassis and most of the sheet metal is gold irridite 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 1958-built SP-600VLF.
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? Performance - Noise versus gain - that's the problem. Certainly the number of times that the SP-600VLF receiver will be operated with AVC on and the BFO off will be very limited. 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.) The only other carrier signals that have easily decoded information would be those from LW BC stations. With LW BC stations tuning is again done with the BFO on and tune to zero beat. This is called an "exalted carrier" type of reception of AM and it helps with weak signals, which all of the LW BC stations are (here in the western USA.) 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 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."

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 found that Selectivity at 1.3kc gives the best signal to noise ratio. A 600Z ohm headset connected to the 600 Z ohm audio output (not the phone jack) gives the best results for weak signal detection. 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 like JJY or WWVB 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. NAA and NLK are very strong as are the other MSK-RTTY Navy VLF stations in the 20kc 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.

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 side panels of the 600VLF

Conclusions - Medium Wave Amateur Operation - Today, the SP-600VLF is rapidly becoming a piece of equipment that may only be able to receive a few interesting signals unless a MW amateur band is granted by the FCC. NDBs are going "off the air" in droves. LW BC stations also seem to be in a similar "disappearing" state. Loran-C is "long-gone." The spectrum below 500kc is rapidly becoming exclusively data transmissions that require special equipment or computer programs to decode. Amateur operation on 472kc to 479kc (600M band) is tentatively approved by the FCC with a 5 watt ERP limit on CW and data transmissions. It should present a challenge on both transmitting and on reception. That part of the spectrum is particularly noisy so a good receiver, like the SP-600VLF, would help. The other amateur LF band around 136kc will present even more challenges due to reception noise and ERP limits. Another use might be in the Lowfer Band. Regs allow 1 watt transmissions between 160kc to 190kc with a 50 ft maximum limit on antenna length. Special computer programs can work with QRSS CW signals which can result is some DX reception but 2X CW (real morse) contacts are extremely rare. In other parts of the world, 136kc is an amateur frequency with a 200 watt power limit. What a difference that is from the 5 watt ERP (Effective Radiated Power) for 600M. So far, nothing planned for 136kc operation in the USA.

The SP-600VLF is a "top notch" LW receiver but using it today is a challenge mostly 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: 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       

UPDATE: For December 17, 2014 - I've been using the SP-600VLF-31 for about a month now (with the loop) and have logged over 100 NDBs, ten of which are newly heard NDBs. The greatest DX is the not-unexpected DDP in San Juan, Puerto Rico - over 3000 miles away, although DDP is not too difficult to hear since it's a 2KW transatlantic beacon. Performance of the SP-600VLF is exceptional and using only 600 Z ohm 'phones for the audio output and running the bandwidth selectivity at 1.3kc or narrower (and with manipulation of the crystal filter phasing) the ability to copy two or three different NBDs on the same frequency is impressive. The six foot loop has certainly made the difference in the ability to copy very weak signals.

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 1 or 2 gives better high frequency audio response which helps the copy with multiple stations on the same frequency.    Feb 4, 2015 - Newly heard NDB is another Hawaiian NDB, POA 332kc copied at 0550PST.


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.

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. 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.

Signal Corps BC-344-D - Covers 150kc to 1500kc in four tuning ranges. IF is 92.5kc. Double pre-selection receiver. Excellent performer on loop or long wire but lack of any selectivity control limits the ability to copy some types of signals in noisy conditions. Good dial accuracy. Difficult to restore due to mechanical design. Receiver is quite heavy for its size. Speaker output and Phones outputs are tied together. Generally, output Z is 4K ohms but can be set internally to 300 Z ohms.

Signal Corps BC-348 (except some A, B and C versions) - covers 500kc to 200kc with SW coverage above 1.5mc - Excellent SW receiver that is pretty good on the MW/LF band if the receiver has been aligned recently. Crystal Filter narrows bandwidth to about 1kc. IF is 915kc on all versions. The original BC-224 and the early BC-348 receivers didn't cover 500kc to 200kc. This band was added early in WWII and many early versions (A, B and C) were reworked to have the MW/LF coverage. There were a few of the early versions that did escape the rework but these are seldom encountered.

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 LW receiver. I've tested and used dozens of different kinds of vintage LW receivers and in my opinion the "best" of the LW receivers all perform at about the same level. While all of the receivers profiled above 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. A close "second" is the US Navy RBA receiver. My third pick would be the National RBL receiver. 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, effective noise limiters and have excellent mechanical construction. However, even these three top vintage LW receivers cannot perform well within certain environments or poor conditions. For effective LW reception you absolutely need the following. First, a good receiving location that has no RFI (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. 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 audio output. You'll never hear the extremely weak signals using a loudspeaker. 'Phones are a must. 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.

Using Vintage Long Wave Receivers

Some of the Signals 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 foreign longwave BC stations. Here are some of the types of signals found below 500kc.

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.

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 although many NDBs are being displaced by powerful DGPS signals within the same part of the spectrum (generally signals from 290kc up to 325kc and 425kc up to 485kc are predominately DGPS signals.) 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. NOTE for 2014: More and more DGPS and other digital data beacons are turning up daily. Expect to find them scattered throughout the normal NDB frequencies.

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. For USA, Canadian and worldwide NDBs, is a good source of information. World Aero Data has almost all NDBs listed but you will have to click on the "Airport Call" to find the actual location. Another good information source is  you'll have to load either the call of the NDB or the frequency into the search parameters and then the page will jump to the listing. You can also scroll down the entire page of NDBs listed by frequency. There are also notes regarding certain characteristics for some NDBs as reported by listeners. Classaxe provides the most information on NDBs. 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.


There other kinds of beacon signals that will be received on LW. Sometimes these are buoys that provide some navigation or hazard information in bays, lakes and other waterways. Sometimes there are small coastal beacons that have taken the place of lighthouses. Many times it is 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 - the few remaining Maritime beacons are not listed on NAV-AID sites (only airport NDBs.) Even legitimate airport NDBs sometimes are not listed in any of the NAV-AIDs, like "marker beacons." This can be an oversight or sometimes it's a new NDB (yes, there are some new ones now and again - 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.

NOTE: 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.

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.

Knowing International Morse - NDBs seldom send faster than 10 words per minute, so it's not really a challenge to copy their call letters when the signal is strong and there's no interference. Being fluent in International Morse is a major advantage when trying to copy several NDBs operating on the same frequency. It is also helpful when the signal is so weak that it's practically at the same level as the noise. 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 your NDB log. Can you still receive and identify NDBs if you can't copy Morse? Yes, mainly because NDBs send so slow. This was intentional since many private pilots were barely Morse proficient (if at all.) The NDBs send slow enough that the "dots and dashes" can be written down and then "translated" into the call letters of the beacon.

More Longwave Signals

In addition to NDBs, there are foreign longwave broadcasting stations. These are generally located in Europe and Asia and 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 few 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. NOTE for 2014: There is now a digital data beacon on 279kc that prevents any copy of Radio Rossii here in Nevada.

"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.

In other countries, 136kc is an amateur frequency that can be used for fairly high power transmissions. The limitations are not nearly as strict as in the "Lowfer" band. In the USA, 22 experimental licenses have been issued under the call WD2XSH/xx. These are licensed individuals that are carrying out experimental transmissions around 500kc (usually 508kc.) The limitations are 20 watts EIRP. About half of the 22 licensees have not gotten "on the air" but some signals can usually be found. In the West, WD2XSH/22 in Sweethome, Oregon is very strong and easy to copy. These signals are CW, not MCW. UPDATE: I haven't heard any activity on 508kc for some time now - 2016

Other LW signals are WWVB (60kc) and JJY (40kc,) both pulse encoded time transmissions. JJY will identify their transmissions in CW at 15 and 45 minutes after each hour. WWVB provides no identification. All Loran C stations used to transmit on 100kc. They were precisely timed signals used for determining position based on the propagation delay. 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 (USAF vs USCG who ran Loran-C.)

The US Navy has several MSK RTTY stations operating from 20kc up to around 50kc, used for world-wide communications with the Navy submarine fleet. MSK is a very narrow shift FSK, called Minimum Shift (Frequency) Keying or MSK RTTY, a signal with only a few cycles shift. All transmissions are encoded, so even demodulating the MSK RTTY signal doesn'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. There are a few more located around the world, operated by the US Navy, including one in Hawaii and one in Australia. The two 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. 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. 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. 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.

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.

SAQ, the Alexanderson Alternator located in Grimeton, Sweden, operates twice a year. Once on Ernst Alexanderson's birthday and once on Christmas Eve. The mechanical transmitter produces a 200KW RF signal on 17.2 kc and operates in the CW mode. Messages transmitted are usually greetings to listeners and relate to whether it's Alexanderson's birthday or Christmas. 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. 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 impossible in the Western USA. 


600 Meters and 2200 Meters in the USA

GOOD NEWS! - 600 Meter Amateur Band Proposal - As of February 2012, there is a proposal to create a world-wide amateur band dubbed "600 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 "600 Meters" will be early 2013.

As usual,...there seems to be a lot of opposition to having US amateurs operate below 1800kc. Here it is 2014 and still the 600M band is going nowhere here in the US. Canada has approved its use. I'm afraid that 600M is going to end up like the 500kc operations - only a few licenses for a few individuals - if even that. -  H.Rogers July 2014   -  SOS, Jan 2015 - SOS 2016 -

Finally,...five years later,...well,...maybe,...but probably NOT! - As of July 2017,....472kc to 479kc is now supposedly an amateur band in the USA with only a few "strings attached." Most modes are allowed at 5 watts ERP. BUT,...don't get your hopes up. Here's the "hold-up." Because certain utility companies run test and troubleshooting data on some types of power transmission lines at some unspecified times and certain officials believe that there might be a slight possibility (not substantiated by any test evidence) that this utility test transmission could be corrupted by amateur interference, the FCC has left the ultimate decision of whether an individual amateur can use the 600M band up to a political lobby concern called the Utilities Technology Commission (the UTC.) The UTC's primary interest is to promote business and commerce for the various Utilities. They are not interested in amateur radio operation unless it could adversely affect the operations and profits of the utility concerns they represent. A further indication that neither the FCC nor the UTC have any real interest in amateur operation on 472kc (or 136kc) is that fact that there is currently no methodology in place for the individual amateur to apply for UTC approval of operation (that is, if you really thought they would grant it to you.)  Supposedly, the UTC and the FCC are "working" on this problem but it's obvious that neither entity has any interests in permitting any regular amateur radio operation in this part of the spectrum. Essentially, this has effectively stopped amateurs from operating on 472kc. (SOS.) On 2200 meters, the ERP is 1 watt. At present, in the USA, operation on 2200 meters requires a special experimental license from the FCC unless you operate with the same restrictions that apply to Lowfers. So, what about those amateurs who want to operate on LF legally and right now without all of the red tape and hassle? The only option is to become a Lowfer.       

Data from ARRL and Wikipedia.


Longwave, or LW, is a general term used to identify wave lengths longer than 600 meters, or all frequencies below 500kc. However, to be more accurate, this region of the radio spectrum is divided into three sections. They are:

 Medium Wave (MW) =  300kc to 3000kc
 Low Frequency (LF) =  300kc to 30kc
 Very Low Frequency (VLF) =  30kc to 10kc

Long Wave Receiver - Generally, this would be a receiver specifically designed for a frequency coverage of 600kc down to 15kc but can be any receiver that has significant LW coverage.

Dealing with the 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 problems when using modern equipment to tune in LW signals but what about vintage gear? How vintage LW gear responds is dependent on the noise environment and the antenna used. 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 noise found on LW is originating from our own houses. Light dimmer switches are notorious for producing an intense "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, some types of "wall wart" power supplies, some types of CFI lamps, some types of 120vac LED lamps can also produce RFI noise. Cleaning up our own houses for RFI noise is the first step towards successful receiving of LW DX.

Another noise producer are 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.

There are so many noise sources today within urban areas that the only solution is to use a shielded-magnetic loop antenna. These antennas 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 mostly responds 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. Most shielded loops will have some kind of amplifier that is either "tuned" or is somewhat "broadband." 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.


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 RTTY VLF stations running around 20 kHz day or night, weaker LF stations, like JJY at 40 kHz, can only be received just before local sunrise and night 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 military communications. The US Navy RTTY stations located around the world are always easy to receive with equipment that can tune low enough - 20kc up to about 50kc.

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 IF frequency. It is the level of the injection that is important to weak signal copy. 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. >>>

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.)


>>>  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. 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. Keeping the 'phones slightly in front of the ears is an effective method to preserve your hearing and is used by experienced CW ops.

Interestingly, RCA built a superheterodyne longwave receiver for the Navy in 1931. The RAA was a gigantic, 465 pound receiver that used 14 tubes and had four different IFs that were individually selected by the bandswitch. Four specifically tuned BFOs were also needed in the RAA. The four different IFs allowed for uninterrupted coverage from 10kc to 1000kc. 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 and later. 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 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 this 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, most 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 HRO (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 a couple of high-end, designed specifically for LW, receivers that were made for the military and for the laboratory. The Hammarlund SP-600VLF is one that has interested a lot of LW listeners since it has continuous coverage from 10kc up to 540kc. It isn't just an SP-600 with LW coils but rather is a completely "designed for LW" receiver that uses the basic SP-600 concept. Unfortunately, it 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 DX reception, it is really necessary to have a low-noise location. The Collins R-389 LW receiver is so rare and so expensive that it is really more of a collector's receiver than anything else. The R-389 performance is usually reported as adequate but not phenomenal however I've never had the chance to operate an R-389 to compare its performance to other LW receivers. It's also likely that many of the R-389 "Collins Collectors" haven't had access to other high-end LW receivers and may not realize that all LW receivers perform best with low-noise loop antennas and a quite location. 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 antenna location rather than the receiver. If the LW superhet user runs his receiver with a tuned loop antenna, he will find the signal to noise ratio is greatly improved and generally with these types of antenna, the superhet performs really quite well. The superhet limitations would be due to excessive BFO injection (required for good SSB demodulation) and AVC operation that can't be switched off which allows the receiver's gain to be controlled by the noise level. Most of the time, these functions are found on some types of modern communications receivers and on shortwave portables, not on vintage receivers.


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.

Tuned Loop Antennas or End-Fed Wires

Though LW stations can be tuned in using almost any type of antenna, the "Tuned Loop" 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. 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. Much longer than 250 feet and the EFW might begin to exhibit "long wire" characteristics of improved directional gain off of the ends although this actually depends on the frequency that the antenna is being used to receive. 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 so) 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 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 tuned loop antenna will always outperform almost any end-fed wire. 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 relatively small tuned loop antennas. However when using WWII or later vintage receivers, either regenerative or superhet, the tuned loop antenna provides the low noise and higher signal strength necessary for successful DX NDB station copy. Be sure to read the section below "Using a 300 ft. Long End-fed Wire up 50 ft." for performance evaluation of a long EFW.

*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.


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.


Using a 300 ft. long End-Fed Wire Antenna up 50 ft.

UPDATE - Summer 2013: Since moving out of Virginia City with its severe RF noise and physical limitations on antenna size, I have now erected a 300 foot long EFW antenna that is about 50 feet high here in Dayton. I hope to use this for many types of reception but I'm especially looking forward to its LW performance. Since I got the antenna up in July 2013, I won't be able to really test how effective it is on LW until November or December 2013. I can say that on shortwave (75M and 40M) it provides about a 2 S-unit increase in signals over a 25 ft. high (at the apex) Inverted Vee antenna. I'll update this information during the winter LW season 2013-2014.

UPDATE - Oct. 2013: As of October 2013, with the LW season getting underway, I've started listening with the RAZ-1 receiver and the 300' EFW. The first listening session was testing from 600kc down to 20kc. Navy stations NAA and NLK were both "bombing in" here on 24.0kc and 24.8kc at about 5PM. It was still too early for any NDBs except FCH 342kc in Fresno and PBT 338kc in Red Bluff. Reno NDB NO 351kc has been off the air for several months now and may not be returning. The next morning at 6:30AM, I logged a new NDB within five minutes. DPY 365kc from Deer Park, WA was coming in fairly strong for a 25 watt marker beacon. We still have to check JJY at 40kc, Radio Rossii 279kc and a few other "test stations" to evaluate how the 300' EFW is working, but so far it seems to pull in signals pretty well with the signals well above ambient noise levels. I'm positive that the Dayton location is very quite compared to "noisy" Virginia City.

UPDATE - Nov 2013: As of November 6, 2013, I've switched receivers and I'm now using the Navy RBA-6 receiver with the 300' EFW. Another new NDB the first listening session, ICL on 353kc - a 25W marker beacon in Clarinda, Iowa. More to come,...

UPDATE - Mar. 2014: I had to take the 300 ft EFW antenna down. During high winds, which are common in Nevada, the static build-up was intense. I didn't have a good earth ground upstairs and could only ground the antenna to the house ground. When I saw the end of the antenna, which was connected to an end fed wire tuner, arcing to the case of the receiver it was setting on,...well, that was enough. I took down the antenna and will re-erect it for the shop where I do have a substantial earth ground system installed. From the shop I can also use the antenna for transmitting. I tried that with the first installation upstairs but with the RF field so close to the house the heating system turned on whenever I transmitted.

Tuned Loop versus the 300 ft. EFW - Even though the 300 ft EFW was an impressive antenna and using it for awhile gave me a chance to compare its performance versus a six-foot tuned loop antenna, I think the noise level on the EFW was much higher than on the Tuned Loop. The signals tuned were usually strong so the actual level that signals were above the antenna noise was good. But, the tuned loop is better. With the loop's low noise, extremely weak signals (right in the noise) can be copied and I don't think that the EFW was able to "dig down into the noise" as well as the tuned loop. The advantage of the EFW was the ability to tune down to 20kc if I wanted to. I just don't have that enormous range with the tuned loop which can only tune from 200kc up to 500kc. The best set-up would be to have both antennas available and to use the tuned loop for NDBs and the EFW for VLF.


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 10KZ ohms.

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.

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. 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 2014

From Virginia City - Most of  the following are NDB stations that I copied from Virginia City, Nevada using only vintage, tube-type receivers. I logged most of these NDBs using the 1941 RAZ-1 receiver, but I have also logged quite a few with the 1945 RAK-7 and 1944 RBL-5 receivers in the past. I also logged some "newly heard" NDBs with the 1920 SE-1420, the 1922 RMCA IP-501A, the 1955 Collins R-390A (485-530kc only) and the 1940 Hammarlund SP-200-LX receivers. For the 2009-2010 season we added the 1945 RBA-6 receiver, the 1952 Mackay 3001A receiver and the RCA CR-91 receiver. The first antenna was a 10' diameter remotely tuned loop that was destroyed by wind. Now, the main 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. The antenna used is now 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 is the RBA-6.   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

Total NDBs logged as of DEC 2016 is 300.

AA - 365kc - Fargo, ND - 100W

ADT - 365kc - Atwood, KS

AEC - 209kc - Base Camp, NV

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

BKU - 344kc - Baker, MT - 80W

BO - 359kc - Boise, ID - 400W

BR - 233kc - Brandon, MB, CAN

BWR - 412kc - Alpine, TX - 25W

CC - 335kc - Buchanan AF, CA - 25W

CEP- 278kc - Ruidoso, NM - 25W

CG - 227kc - Castlegar, BC, CAN

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

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

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

DWL - 353kc - Gothenburg, NE - 25W

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

EHA - 377kc - Elkhart, KS - 25W

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

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

GC - 380kc - Gillette, WY

GDV - 410kc - Glendive, MT - 100W

GEY - 275kc - Greybull, WY

GGF - 359kc - Grant, NE

GLS - 206kc - Galveston, TX - 2KW

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

HCY - 257kc - Cowley, WY

HDG - 211kc - Gooding, ID - 50W

HE - 245kc - Hope, BC, CAN

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

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

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

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

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

PPA - 450kc-Puerto Plata, Dominican Republic

PRZ - 407kc - Portales, NM - 25W

PTT - 356kc - Pratt, KS - 25W

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

QV - 385kc - Yorkton, 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

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

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

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

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

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

UVA - 281kc - Uvalde, TX - 25W

VC - 317kc - LaRonge, SK, 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

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

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

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

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

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

ZEG - 379kc - Edmonton, AB, CAN

ZF - 356kc - Yellowknife, NWT, CAN

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

ZP - 368kc - 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

Z5 - 274kc - Vulcan, AB, CAN

Z7 - 408kc - Claresholm, AB, CAN

3Z - 388kc - Taber, AB, CAN

6T - 362kc - Foremost, AB, CAN










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,



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- 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 1997/2017