Radio Boulevard
Western Historic Radio Museum
 

Shipboard Radio Receiving Equipment
1918 up to 1927

~ PART  TWO ~

1.  SE-1420 - Navy Dept.-Bureau of Engineering - Wireless Specialty Apparatus Co.
2.  IP-501-A - Commercial - Wireless Specialty Apparatus Co. for RCA
3.  IP-503 - Long Wave Loading Unit - Radiomarine Corporation of America

Histories, Circuit Designs, Operation
Restorations of SE-1420, IP-501-A including 2026 Revisits to the Workbench

Performance Testing with Reception Logs

Operating 100 year old LF-MW Radio Equipment in
Today's Polluted Long Wave Electro-Magnetic Environment

~ Part One covers SE-143, SE-1387, SE-1834 ~

by: Henry Rogers - Radio Boulevard-Western Historic Radio Museum

SE-1420 Receiver (NESCO,) Kennedy 521 Two-Stage Audio Amplifier, Music Master Horn Speaker, 2KW Quenched Gap Transmitter (built by Wireless Specialty Apparatus, Kilbourne Clark Mfg., Federal Telegraph Company and others)

From Sterling's "The Radio Manual" 1st Edition 1928

With the introduction of the SE-1420 (in 1919) the design of the typical Navy receiver advanced significantly. The SE-1420 provided its own on-board vacuum tube regenerative detector allowing it to function adequately without any additional accessories. The internal shielding of the entire receiver, both cabinet and front panel, allowed its oscillating detector to operate with excellent stability with no hand capacitance effects when tuning the receiver. When built for commercial users the SE-1420 was slightly changed becoming the IP-501 that was offered with an external two-stage audio amplifier. Within a short time, the IP-501-A was introduced, a receiver that combined the IP-501 with a built-in two-stage audio amplifier to provide a completely self-contained receiver capable of providing excellent communications for all types of shipboard installations. The IP-501-A design was so successful that it was still in-use onboard commercial ship and coastal station installations as late as 1942.

SE-1420, IP-501 and IP-501-A Receivers
IP-503 Long Wave Loading Unit for the IP-501-A
History, Design and Construction, Performance Testing

Artwork from:  "How to Make Commercial Type Radio Apparatus" by Milton B. Sleeper - 1922

Wireless Specialty Apparatus Company  SE-1420B  Serial Number: 270R 
Tunes from 235 meters to 7500 meters. Has upgraded Fil. voltmeter.    2026 photo

SE-1420 Circuit Design - Hazeltine first utilized a three-circuit tuner, that is, adjustable tuning of the antenna circuit, variable coupling to the tuned detector grid circuit and the detector plate circuit, to provide excellent sensitivity. He then used a completely shielded cabinet and isolated the Antenna Tuner circuit from the Secondary Tuner circuit with another shielded panel. This complete shielding would eliminate any stray pick up, hand-capacity effects or any coupling between the two circuits. Using a sharply tuned Antenna Tuner helped to improve selectivity and reduce adjacent frequency interference. By using a small Coupling Coil mounted inside the Antenna Coil and only allowing the energy from the Coupling Coil into the Secondary Tuner, further reduction of unwanted signals was realized. The two main inductors used bank-wound Litzendraht wire coils to reduce capacitive losses. "Dead turns" on all switched inductances were grounded by the action of the switches to further reduce losses. All of these efforts increased the selective nature of the SE-1420's tuning ahead of the detector input. The tuning was at first specified at 235 meters to 7500 meters (1275kc to 40kc) but most receivers would tune up to 8000 meters (37.5kc.)  AMRAD versions specified 250 meters to 7500 meters. Some later specifications stated 300 meters to 8000 meters.

The initial SE-1420 design used a negative-biased triode detector that didn't require a grid capacitor or a grid leak resistor. The grid was "self-biased" and involved the grid to filament potential differences that would allow the tube to perform rectifier functions or detection. The filament current control adjustment was a special rheostat that was tapped and provided the A- connection with a 2 ohm fixed value before connecting to the current meter (that could measure current flow in either direction) and the VT filament. Adjustment of the filament current and the plate voltage were critical for proper grid bias in relationship to the filament voltage. Later versions of the SE-1420 installed a grid-leak type of detection that was easier to use. When SE-1420 receivers were rebuilt by the Signal Corps into BC-131 receivers, a grid-leak was added to the detector as part of the upgrade. The later IP-501 versions also used the grid-leak detector.

NOTE: I've owned the SE-1420B shown to the left since 1990. Restoration details further down this article.

The detailed design effort was necessary because all Navy (and most other maritime vessels) used either spark or arc transmitters (that sent FSK signals which were deliberately wide-spaced f-shifting) which produced very broad spectrum signals. Early receivers were so insensitive and tuning so crude that the broad transmitted signal was usually an advantage at attracting attention. The inability to have simultaneous operation of nearby stations led to sharing "airtime" - a gentleman's agreement that allowed most wireless operators to co-exist. Wartime was a different situation however and better, more powerful transmitters required better, more selective receivers. As the spark gap transmitter was improved by employing an oscillation transformer that narrowed the bandwidth, the receivers became more sensitive but not necessarily more selective. They still responded to the fairly broad spectrum signals that prevailed. At the time the SE-1420 made its appearance, its ability to successfully function in the presence of nearby spark and arc transmitters made it an instant necessity for all sea going vessels.

from Milton B. Sleeper's 1922 booklet "How to Make Commercial Type Radio Apparatus."

Westinghouse Type RB Medium Wave Receiver
 this receiver was in Ralph Muchow's Radio Museum in Elgin,IL

 photo from Radio Age, Nov '82

The U.S. Army Signal Corps BC-131 version of the SE-1420C. This example has the olive-drab painted wooden case. Note that an extra binding post has been added to the right-side vertical terminals to provide access to the Tickler coil (this became standard in later versions.) 
Photo from Antique Radio Classified, cover, Nov. 2006

Tubes Used - Tube types used in the SE-1420 depended on the time period and the end user. In early receivers, generally, if the Navy used the SE-1420, a Moorhead Electron Relay (ER, also SE-1444) was used as a detector, while the Signal Corps preferred the Western Electric VT-1 (also, CW933, WE "J".) General Electric also made the CG890 Type "G" tube. The Western Electric CW933 was preferred for its ease of adjustment for oscillation. The variety of tubes all used plate voltages in the 25vdc to 45vdc range. There were many variations of the Moorhead ER tubes with different manufacturers building them from 1919 up to the early twenties (Atlantic Pacific and American Marconi.) Both the VT-1/CW933-J and the ER/SE-1444 tubes specify filament current rather than voltage (.5A@ ~3vdc for the VT-1 and .4A@~4vdc for the ER.) There were other tubes also available, like the military triodes that had the internal structure mounted so that when the tube was operated in the horizontal position (as in the SE-1420) the actual tube structure is in the vertical position. This prevented filament sagging that could happen with standard tubes operated in the horizontal position. By about 1925, most SE-1420 receivers were using the 201A and these tubes specify filament voltage (5vdc@.25A.) These receivers were also generally converted to Grid Leak detectors.

Detector Selector Switch - The lever operated low-loss switch marked CRYSTAL OR R.F.AMPL - SEND - AUDION allowed the user to select either a mineral detector or a vacuum tube detector. The receiver circuits are routed through this 4P3T switch that controls four circuit lines to allow a Crystal Detector to be used while bypassing the vacuum tube detector. In AUDION, the crystal detector circuits are bypassed to allow a vacuum tube detector to operate. The Crystal Detector is connected to the CRYSTAL terminals on the lower right corner of the front panel. SEND disconnected both circuits for a standby position. Maritime and USN regulations required all shipboard radio stations to have a crystal detector receiver that could operate without vacuum tubes or voltage requirements in case of an emergency where ship's power, batteries or tubes were rendered useless and a method of receiving had to be available.

U.S. Coast Guard CGR-5A from June 1927 - New SE-1420 receivers were built through most of the 1920s by several different contractors over the years. Shown in the photos to the right is the CGR-5A, made for the Coast Guard on a contract dated June 6, 1927. This version doesn't have the buzzer or the Detector selector switch and is housed in a metal cabinet. Also, the dial is calibrated in frequency rather than meters. Note that the receiver has five vertically aligned binding posts on the right-side of the panel indicating that the TICKLER access binding post had become a standard feature. The contractor on this particular CGR-5A was NESCO. This version also references itself to the SE-1420C as indicated on the CGR-5A data plate, "similar to Navy Type S.E. 1420-C/Army Type BC-131."  

1927 - CGR-5A built by National Electrical Supply Company for the U.S. Coast Guard
This receiver belongs to Chris Dockery, who has provided these photos.

The ID tag on the CGR-5A showing the contact date of June 6, 1927. The receiver was built sometime after that date.

Wireless Specialty Apparatus Company, United Fruit Company and the IP-501

In 1907, Wireless Specialty Apparatus Company (WSA) was formed by Greenleaf Pickard (who had cataloged over 1500 minerals and combinations that worked as detectors in 1903 - Pickard didn't discover the crystal detector, Karl Ferdinand Braun of Germany had invented the point-contact diode in the 1890s.) Additional WSA associates were Col. John Firth and his patent attorney, P. Farnsworth. John Firth also worked with Reginald Fessenden's NESCO at the same time and, probably because of this association, all WSA model numbers have the "IP" prefix which meant "Interference Preventer" - a Fessenden term for "selective tuning." United Fruit Company was an early user of WSA gear on their ships and in their shore stations.

United Fruit Company had been somewhat in the radio business since 1903 and, in 1911, they bought WSA. Later, in 1913, United Fruit formed another radio company, Tropical Radio Telegraph Company, mainly for setting up and operating communications around their extensive property holdings in Central and South America. United Fruit was aware that their purchase of WSA gave them all rights to all Crystal Detector patents that WSA had through Greenleaf Pickard's association. The crystal detector dominated wireless receiver operation, especially through WWI. Right after WWI, the crystal detector patents were still of major importance and because of this patent, United Fruit Company was invited into the new cross-licensing agreement that was headed by General Electric and included Radio Corporation of America (GE's creation in 1919) along with AT&T (vacuum tube patents - their manufacturing facility was Western Electric) and Westinghouse (Regenerative Detector and Superheterodyne patents and International Radio Telegraph Co.)

With the cross-licensing agreement, these companies shared patents and products toward their advantage and tried to exclude most other companies and their competition by threats of lawsuits. The cross-licensing also allowed UF/WSA to now produce the SE-1420 for commercial users and have them sold by RCA (RCA hadn't created a division specifically to handle all maritime equipment and operate coastal communications stations - yet.). For the commercial market, in 1921, the IP-501 was introduced. It was an updated design of the SE-1420 receiver. Tuning was 300 meters to 8000 meters. Access to the Antenna LC, Secondary LC and the Tickler L was provided by three pairs of binding post terminals at the top of the front panel. Although early versions may have used ERs or VT-1s, after about 1923, the IP-501 receivers used 201-A tubes. The filament meter was changed from a current meter that was used on the SE-1420 to a more useful voltmeter.

IP-501 with Triode Type B Amplifier and IP-503 Long Wave Loading Unit.
    From: George Sterling's "The Radio Manual" 1st Edition - 1928

What the "CRYSTAL OR R.F. AMPL" was Used For - Both the SE-1420 and the IP-501 had the CRYSTAL OR R.F. AMPL position accessed with the Detector selector switch. It was possible to use the CRYSTAL terminals as an input for the output of an RF amplifier. In the CRYSTAL-RF AMPL position there's no access to the IP-501 detector grid so the external RF amplifier required its own detector. The SE-1405 RF Amplifier is mentioned in the SE-1420 manual with instructions for its hookup to the receiver but no details are provided on the SE-1405 itself. Later, in 1922, the USN and NESCO did provide various types of "add-ons" for these receivers and RF Tuners, including the SE-1834A that provided a three-stage RF amplifier, detector and two-stage audio amplifier. Since the SE-1834 would only need the IP-501 ANT LC and SEC LC tuners, using this type of device in the CRYSTAL-RF AMPL position would function as intended.

RCA, Radiomarine Corporation of America and the IP-501-A

IP-501-A as produced from about 1922 up to around 1926. This is the early version with a Telephone Condenser switch and nickel-plated binding posts. Wireless Specialty Apparatus built these receivers for RCA from 1922 up to around 1924 when RCA acquired the Wireless Specialty operation. In 1927, RCA combined Wireless Specialty with another acquisition, Independent Wireless Co., to form Radiomarine Corporation of America. From 1927 on, the data plates on the IP-501-A will indicate Radiomarine Corp. as the builder.    2026 photo

In 1922, the IP-501-A was introduced. It combined the IP-501 and the Triode Type-B Audio Amplifier into one long cabinet. The consolidation made the IP-501-A easier to build and, certainly much easier to set up and use, since everything necessary was in one cabinet rather than two separate units as in the IP-501 and Triode Type B amp. The later versions (by 1927 at the latest) of the IP-501-A eliminated the Telephone Condenser switch circuit and replaced all of the nickel plated binding posts with bakelite capped binding posts.

At the time the IP-501-A was introduced, the general public had become interested in the new Radio Broadcasting. The market for entertainment radios sky-rocketed and most manufacturing concentrated on radios for broadcast reception. The commercial maritime radio market was limited when compared to the consumer entertainment radio market and because of this the IP-501 and IP-501-A production level was never really very high. Wireless Specialty Apparatus built some home radios for RCA to sell, the AR1375, for example.   >>>

>>> RCA handled the sales of IP-501 receivers and accessories from around 1921 until sometime in 1923. By 1924, Wireless Specialty Apparatus apparently disappeared from the scene, apparently purchased by or, at least, operated by RCA. It's likely that RCA acquired or assumed management of the WSA manufacturing plant since all later IP-501s and IP-501-As were built still using WSA parts. The data plates on receivers built from about 1922 to 1926 have "Built by Wireless Specialty Apparatus Company for Radio Corporation of America" indicating an exclusive production arrangement. In 1927, RCA acquired Independent Wireless Company and it was combined with Wireless Specialty Apparatus to form Radiomarine Corporation of America. Independent Wireless' Chas. Pennill became Radiomarine's Vice-President and J.P. Duffy came from RCA to act as Superintendent of Production. With the formation of RMCA, all of RCA's marine operations and sales were then transferred to Radiomarine Corporation of America as a division of RCA. From 1927 on, the IP-501-A and its accessories had "Radiomarine Corporation of America" on their data plates.

By the late twenties, the design of the IP-501 family of receivers was beginning to show its age. However, RMCA continued to build these robustly built favorites of Maritime Radio Operators. It was very common for commercial ship owners to never upgrade the radio equipment unless absolutely no other choice was available. As a result, many IP-501-A receivers were still in use all through the 1930s and only being pulled from shipboard service during WWII. Their operation was easy, they were reliable and their excellent performance in the hands of experienced radio ops had resulted in the receiver becoming the "standard" shipboard receiver for almost two decades. Many RMCA Coastal Radio Stations had IP-501-A receivers setup all through WWII. Advertising for RMCA was still using photographs of shipboard and Coastal Station installations showing the IP-501-A as late as the post-WWII time period. The selling price of the IP-501-A was $550 in 1922 (listed in "Radio Enters the Home," a catalog of products available through RCA though built by WSA at that time.)

In March 1930, RCA acquired most of the patents and power that had formerly been shared by the GE-Westinghouse-AT&T Group as part of a settlement of an Anti-trust suit brought by the government. That resulted in the consolidation of RCA into the omnipotent corporation that controlled nearly everything in radio in the thirties and forties. By the thirties, RMCA was running many of the Coastal Stations that provided Radiogram service to ships at sea. RMCA built marine radio gear that was installed on commercial ships. During WWII, RMCA supplied the Liberty ships with radio gear. Around the mid-1960s, RMCA was eliminated as a division and RCA handled all of the maritime business directly - at least, what was left of it.

United Fruit Company went on to political involvement in some Central and South American countries in an effort to protect and/or enhance their extensive banana and pineapple properties. Eventually, United Fruit Company merged to become United Brands (in 1970) and then was reorganized in 1984 as Chiquita Brands International.

NOTE:  I've owned the WSA IP-501-A shown to the left since 1979. Full restoration details further down this article.

RADIOMARINE CORPORATION OF AMERICA
NEW YORK, N.Y., U.S.A.

The 1927 Version of the IP-501-A

The photo left is a close up of the ID tag of an IP-501-A showing Radiomarine Corporation of America as the builder of the receiver. The smaller tag indicates that this receiver was used commercially. These tags are from the receiver shown in the photo right - a beautiful later RMCA version of the IP-501-A. This receiver is probably from the 1927 to 1930 time period. Note that the telephone condenser switch was eliminated and bakelite capped binding posts are used on these later receivers.

both of these great photos are from: Grant Kornberg - "TechnoGallerie"

RADIOMARINE CORPORATION OF AMERICA
NEW YORK, N.Y., U.S.A.

 

LONG WAVE LOADING UNIT

TYPE IP-503 FOR USE WITH IP-501-A RECEIVER

SN: 500,006

When the LW Loading Unit was reinstalled into the cabinet, I found that the Primary Coil slightly contacts a "ripple" on the sheet metal shield at the rear of the cabinet. It only happens at maximum coupling and it's a very slight contact, so it really isn't a problem. I wiped the panel with a dry flannel cloth. Next is the operational test working with the IP-501-A receiver.

Inside the IP-503 - massive loading coils and a lever-driven sliding-rack switch

Close-up of the sliding "knife-type" WAVELENGTH switch shown in the MEDIUM wavelength position

Operation of the IP-501-A with the IP-503 Long Wave Loading Unit
 

SHORT - Since this position shunts the PRI LOAD, SEC LOAD and LONG WAVE TICKLER terminals on the IP-501-A, the receiver operates as it would if it was setup in the standard configuration without the IP-503. AM-BC band from about 1000kc down to 540kc is at the upper end of the coverage and WWVB 60kc is a strong signal near the lowest end of coverage. Regeneration is easily adjusted at any frequency. The IP-501-A will tune down to about 37.5kc (8000 meters) but WWVB 60kc (5000 meters) is the lowest frequency, strong, recognizable signal that can be received during the daytime. JJY 40kc can be received in the early morning before sunrise. Expected frequency range in SHORT is 1000kc down to 40kc.

MEDIUM - This position leaves the ANT (PRI LC) connected in series but adds the loading inductors for the Primary and Tickler circuits. The Secondary inductance is operating from the tap on the coil providing a mid-range inductance addition. The highest frequency, recognizable station received in MEDIUM was WWVB 60kc. Just about the strongest station heard was NPG on 55.5kc, a USN MSK station operating from Dixon, California (the closest USN MSK LF station at 132 miles distance but it doesn't operate often and is mainly in the test and standby mode.) Using the HP-3312A Function Generator as a marker, 65kc with the highest frequency tuned (4700 meters) and 28kc (10,000 meters) was the lowest frequency tuned. It was very easy to tune in the 40kc marker meaning that JJY 40kc would probably be better received in MEDIUM. Regeneration is easily attained anywhere in the MEDIUM wavelength position. Both the IP-501-A Tickler control and the IP-503 Tickler will adjust regeneration. Likewise, both Coupling controls will affect the coupling between Primary and Secondary circuits. Expected frequency range in MEDIUM is 65kc down to 28kc.

LONG - This position connects the ANT (PRI LC) in parallel for a Hi-Z at resonance which performs better at lower frequencies. The LONG tuning range is 39kc at the high end and 16kc at the low end. These frequencies were determined using the HP-3312A as a marker generator for accuracy. Although 16kc was tuned by using the HP-3312A as a marker, NPM 21.8kc, the USN MSK Submarine Communications Station in Lualualai, Hawaii was the lowest frequency recognized station received. NAA 24.0kc in Cutler, Maine was also received as was NLK 24.8kc in Jim Creek, Washington. To confirm which USN MSK station was being received, the HP-3312A (with Digital Freq. Counter attached) was zero-beat with each station to verify the received frequency. Above 25kc and up to 39kc, some carriers were heard but these, although fairly strong, were not readily identifiable and could be any number of various utility type signals. Expected frequency range in LONG is 39kc down to 16kc.

Testing the IP-503 with the IP-501-A   2026 photo

SE-1420 and IP-501-A - Receiver Circuit and Construction Details

The "COUPLING" control rotates a small coil located at one end of the Antenna Coil. The wires from the Coupling Coil are placed next to the front panel shield and then routed through a small opening at the base of the vertical shield that divides the cabinet into two shielded compartments. Only the energy within the variable Coupling Coil is transferred to the Secondary Tuner circuit. The shielding provides complete isolation and eliminates stray pick-up or any hand-capacity effects when operated as an autodyne detector. What comes down the antenna and is tuned in the Antenna Tuner circuit is then variably coupled into the Secondary Tuner circuit. This provided the excellent selectivity necessary for operation of the receiver in the presence of nearby spark and arc transmitters.

The Secondary Tuner circuit is labeled "SECONDARY CONDENSER" and "SECONDARY INDUCTANCE" - this is the main station selector tuning. The Secondary Inductance control selects the tuning range via the tapped inductance, "dead turns" are shorted to ground and the Secondary Condenser tunes the receiver frequency within that range. An articulated pointer shows which tuning range has been selected. On the IP-501 and IP-501-A, the Secondary Condenser dial is scaled in both Degrees and Meters with the various bands covering 235 meters up to 7500 meters, or approximately 1275kc down to 40kc and the condenser is gear driven, (most receivers will tune somewhat higher than 1275kc - 235 meters - and will tune down to 37.5kc - 8000 meters - the later tuning specs were 300 meters to 8000 meters although 235 meters to 8000 meters would be typical. My SE-1420B tunes from 1400kc - 215 meters to 37kc - 8000 meters.)

In some photographs, it appears that the first SE-1420 receivers may not have had a calibrated "SECONDARY CONDENSER" scale other than the 0-180º scale. If this was the case, it wasn't long before a wavelength calibrated dial scale was incorporated. Interestingly, the SE-1420 dial indicated the wavelength directly while the SE-143, the IP-501-A dials (and others) indicated wavelength as a numeral with a factor of "MULTIPLY BY 100" on the dial. Also included on the dial were "letters" that indicated important wavelengths (see photo to the left.) This was used as a reference for military wavelength assignments. The letters made set up and tuning easier for inexperienced radio operators. The SE-1420 lettered scale runs from "F" = 300 Meters up to "W" = 7500 Meters. The lettered scale is red while the meter scale is black. Late SE-1420 receivers, e.g. CGR-5A 1927, had dial scales calibrated in frequency rather than meters. Secondary Condenser dial from an SE-1420B receiver showing lettered scale. Also note that the receiver serial number is on the dial, "270R."

The detector is a regenerative type using a variometer-tickler built into and onto the secondary coil form. Variometer controlled regeneration relies on detector tube inter-electrode capacitance and the EM field coupling of the variometer rotor's position in relation to the tickler coil. The stator consists a stationary tickler winding and a Secondary Inductance extension winding providing close coupling between the rotor and stator of the variometer. For reception of damped wave spark transmitters using rotary gaps the "TICKLER" is adjusted to a setting just before the oscillation point. If an arc transmitter was to be received then the "TICKLER" can be set into the oscillation point to allow a heterodyne action (autodyne detector) to hear the arc signal since it is continuous wave or CW (the Arc transmitter actually sends FSK, frequency shift keying, since the arc is constant and can't be "keyed" by shutting it on and off. By shifting the frequency with keying, the correct Intn'l Morse would be received by tuning in the higher of the two frequencies.) For the reception of a voice transmission via AM, the "TICKLER" would be set to just before oscillation occurs. The greatest sensitivity and selectivity occurs just at either side of the oscillation point in a regenerative detector and that is usually where the operator would adjust his "TICKLER." Since the load on the "TICKLER" (plate variometer) is fairly constant (because of the Antenna Tuning) there is very little change in where the "TICKLER" is set until the receiver is operated below 100kc. The regeneration point is dependent on many factors, but always lower frequency reception will require a little more total variometer inductance so the "TICKLER" control will have to be increased (higher on the scale) as frequencies below 100kc are tuned. The "TICKLER" tunes minimum-to-maximum total inductance in 90º of rotation and then down to minimum L in the next 90º with sign changes happening in quadrants. Depending on how the receiver is setup, all "TICKLER" action is usually between just above 0º and increases to slightly higher than 90º as the lowest frequencies are tuned. The push button switch labeled "OSCL'N TEST" is for testing if the detector is actually oscillating or not. If the button is pushed, it shorts the TICKLER coil and, if the detector was oscillating, a "click" will be heard in the earphones. If no click is heard that indicates the detector is not oscillating and the "TICKLER" control needs to be adjusted. When the SE-1420 was rebuilt to become a BC-131, an additional terminal was added just above the TELEPHONES terminals for TICKLER coil access.

The Antenna Tuner section of the IP-501-A. Note the gear drives on the Antenna tuning condenser. Also, the Buzzer coupling to the Antenna circuit can be seen (the wire coil wrapped on the antenna inductance wiring.) The fixed condenser connects B- to ground (shielding.) The fixed condenser is a .012uf Faradon - the WSA/RMCA brand name.   photo 2008

The "TELEPHONE CONDENSER" switch allows selecting various values of input capacitors to the RF pi-network low pass filter that is connected between the output of the TICKLER variometer and the audio output line. The RF LP filter also uses a series iron core choke and a fixed output capacitor. The selectable input capacitors allow varying the audio response, specifically rolling off the high frequency audio. This is particularly effective for relief from static and other atmospheric noise. Additionally, the particular input capacitor selected would also have an effect on the regeneration and could sometimes be used to skew the TICKLER adjustment in an advantageous manner. Sometimes, when it was difficult to get the detector to oscillate, changing the position of the TELEPHONE CONDENSER would help facilitate regeneration. The TELEPHONE CONDENSER switch is only on the WSA versions of the SE-1420. It is also on the early versions of the IP-501 and IP501-A. The Telephone Condenser (TC) switch was never used in the AMRAD SE-1420 and was eliminated from the later versions of the WSA receivers. The TC switch was really not a necessity. It was probably installed on the WSA receivers for shipboard operation where static and antenna noise can hamper reception and to help with regeneration setups. RCA/RMCA eventually eliminated the TC switch, probably because of expense, potential problems and the fact that an optimum fixed-value capacitor with choke and output capacitor (low pass pi-filter) resulted in effective static relief along with increased reliability by eliminating the switch. Also, the effect on regeneration was not all that important since there were many other ways to achieve the same results.

The other option is R.F AMPL. By using the lower TELEPHONES terminal as the RA connection and the upper CRYSTAL terminal as the RE connection these terminal provide access to the Secondary LC tuner if the XTAL/R.F AMPL is selected with the Operation switch. This would allow the SE-1420 or IP-501 to provide the RF Tuner functions necessary for an external RF Amplifer, Detector, Audio Amplifier, such as the SE-1834A. The SE-1405 is mentioned in the SE-1420 manual as a compatible RF Amplifier that connects in a similar manner. The entire Antenna and Secondary LC tuners and the Coupler of the receiver are utilized and only the detector tube is bypassed.

The "BUZZER" provides a "signal generator" of sorts. When looking for a sensitive spot on the crystal detector, it would help if a really loud signal was present. Pressing the buzzer button will actuate a small electro-mechanical buzzer that arcs and creates tremendously strong, wideband RF signal (intense static noise, actually.) This is coupled into the antenna circuit with bare wire coil wrapped around the antenna wire to the Primary Inductor in the receivers. The buzzer battery is usually a 1.5vdc dry  cell battery. It's not critical, but 2vdc was considered the maximum for the buzzer. DO NOT PRESS the buzzer button (with Buzzer battery connected) while in the vacuum tube mode of operation - if you do and you're using 'phones in the AF2 jack, the resulting "signal" will be so intense that you probably won't be able to hear anything for a few minutes afterward (yes, I did it.) The Buzzer circuit was only for finding a sensitive spot on a crystal detector.

The Secondary Inductor switch assembly. Tickler control  is on the right. Note the vertical gear-driven "lifter" for the dial pointer. The wooden shaft under the TICKLER control is the OSCL'N TEST button. This unit is from the SE-1420B receiver.

The copper shielding inside the IP-501-A cabinet is painted black. Note the divider shield and the small notched opening that allows the two wires from the Coupling Coil to pass through to the Secondary Tuner. Also note that the tapped screw mounts that allow the panel to be mounted are connected to the box shielding and these mounts also contact the back panel shield for a completely shielded enclosure.

The oak box that the receiver is mounted in is entirely lined with copper sheeting to act as the shielding. Complete contact is assured by way of the metal screw mounts that contact the receiver's panel shielding. Early receiver boxes for the SE-1420 had some sort of strap provided but usually only the side metal guides remain. The ID tag is located on the side of the box and these are almost always missing. There really doesn't seem to be any specific reason why so many military data plates were removed. Maybe it was "military surplus" regulations of the time although it seemed to heavily depend on the particular dealer involved. It wasn't ever a consistent practice to remove the data plates. Weight of the box with all of the copper inside is substantial and the entire receiver is quite heavy for a battery operated receiver,...about 40 lbs for an IP-501-A. The box for the SE-1420 is similar in construction but the shielding is not painted and is left bare copper. The finish on the SE-1420 box is somewhat dark, usually about the color of "iced tea." The later IP-501 and IP-501-A receiver boxes are finished in beautiful golden oak. Most BC-131 boxes were painted olive-drab and one IP-501 and Triode Type-B amp were found with their cabinets painted black though this appeared to be a later treatment that was easier than refinishing the oak. The front panels are .312" thick and is made of "Hard Rubber" sometimes called "Condensite" or "Bakelite-Delecto." This material is not brittle like bakelite or formica. The manuals say that the panel can be wiped with oil to protect it. Probably, with all of the salt-air present onboard a ship at sea, wiping oil on the entire panel, dials, knobs and cabinet would have gone a long way to protect the receiver's overall finish.

All screw and nut connections in the receiver are tightened and then soldered. This method is also used on the mechanical assembly. Soldering is easily accomplished since all of the hardware is nickel plated brass. This securing of all joints with solder was necessary because of the constant vibration of the ship while at sea in addition to adding protection from salt-air corrosion problems. The solder joint itself is not particularly strong and can easily be disassembled, however, much like modern "Loc-tite," it was meant to keep the screws and nuts secure after tightening.

1918 - Initial design of the SE-1420 by Louis Hazeltine
1919 - First contracts for the SE-1420 - AMRAD, WSA and Sperry Gyroscope
1919 - RCA is formed from GE assets and purchase of American Marconi Co. (Nov-1919)
1920 - SE-1420 contracts are extended
1921 - Cross-licensing with GE-RCA group allows WSA to build the commercial IP-501 for RCA to sell
1922 - Design of the IP-501-A
1922 - IP-501 and IP-501-A available from RCA acting as sales agent for WSA
1923 - Likely purchase of WSA assets by RCA.
1924 - SE-1420 contracts continue, National Electrical Supply Co. (NESCO) added to list of builders (after AMRAD's bankruptcy)
1925 - RCA continued with the WSA production of the IP-501 and IP-501-A using Faradon and WSA parts.
1927 - Official formation of Radiomarine Corporation of America using WSA assets and Independent Wireless Company with Radiomarine becoming a division of RCA
1927 - IP-501-A updated - eliminated Telephone Condenser switch, bakelite capped binding posts, data plates indicate "Radiomarine Corporation of America" as the builder
1927 - CGR-5A (SE-1420C) contract, National Electrical Supply Co. (NESCO,) June, 1927
1928? - Production continues through 1928? 1929? 1930?...
1930s - Manuals date-stamped as late as Dec.1938 were provided by RMCA
1940s - IP-501A receivers used up to 1940, removed from most commercial ships prior to and during WWII

Restoration and Operating the SE-1420, IP-501 and IP-501-A Receivers

Most SE-1420, IP-501 and IP-501-A receivers that are found today are far from complete. It isn't unusual to find the receiver missing all of its buss wiring or missing major components and almost always some of the minor parts will be gone. I one time found the Antenna Tuning Condenser of an IP-501 that had been "sawn" out of the front panel - not dismounted from the panel - just sawn out, panel and all. Such destruction was common. Anything is possible to find since these receivers were considered surplus unusable junk in the forties and fifties. How likely your receiver is able to be completely restored depends on your interest, your abilities at replicating parts and how much of the receiver you have to start with.

Generally, the major parts necessary for considering a complete and functional restoration of the receiver are:

1. Both Antenna and Secondary Inductors - including Coupling Coil and Tickler Coil. The Inductors are bank-wound Litzendraht wire and have multiple layers and taps that are wound on machine grooved forms - difficult to replicate. The Inductor switching are also complex assemblies.

2. Both Antenna and Secondary Condensers - complete with gear drives. These condensers and their gear drives are also very complex assemblies.

3. Complete Front panel and all shielding - includes both main dials. The dials are German Silver and difficult (impossible) to replicate.

4. Cabinet and cabinet shielding - though the receiver will operate without the cabinet, it's complete shielding is an important part of the design.

Most of the other parts can be found or replicated. Some parts are not too difficult to find even today. You will probably have to adapt some of the parts from 1920s TRF battery radios. Many times these are the exact same parts anyway. Knobs can be cast or professionally reproduced. Hardware can also be machined and nickel plated. The amount of work necessary is sometimes daunting but patience is required when restoring receivers that are now exceeding 100 years of age.
 

SE-1420, IP-501 and IP-501-A  -  Schematics and Documentation

Documentation is very important when restoring the SE-1420, IP-501 and IP-501-A receivers. Many years ago, it was impossible to find anything for documentation on these receivers except the scant information in period wireless books. With the advent of the Internet and its continued growth as the ultimate information resource, nowadays, complete manuals and schematics can be found. Al Klause's www.skywaves.ar88.net has a lot of information on early Navy receivers including manuals for the SE-1420, SE-143 and the IP-501-A. These manuals do contain schematics but they are somewhat like wiring diagrams, which is actually better for restorations.

The various schematics shown in old wireless books, e.g., Elmer Bucher's book on Wireless Equipment or early editions of George Sterling's "The Radio Manual" or others, all are incomplete or simplified schematics that sometimes have errors. The schematics were only provided as general information. The IP-501 schematic shown to the right is an example of the type of schematic found in wireless books. Note that the Grounding Condenser is shown as a variable capacitor, it should be a fixed-value capacitor.

In addition to schematics and manuals, good photos of the interior of original receivers are invaluable for determining what's missing or exactly how to route wires if they've been removed from the receiver being restored. Be aware that the buss wiring techniques and routings changed over the production period, so early receivers look very different inside from the later versions of the same model. Interior photos combined with manuals and schematics are the most helpful to determine what is correct. Since the advent of eBay, which has now had many auction-sales of SE-1420, IP-501 and IP-501-A receivers, photographic documentation of these models has become excellent. However, it's up to the interested restorer to go in and "save" these photographs because eBay doesn't keep them available very long.

The manual for the RMCA version of the IP-501-A and the manual for the SE-1420 are both available on www.skywaves.ar88.net website. Look in the section marked "Communications Receivers - Navy."

Sterling's "The Radio Manual"  First and Second Editions just have basic operating instructions for both the SE-1420 and the IP-501. The circuit descriptions for both receivers are provided but schematics weren't included for the IP-501 or SE-1420 in the Radio Manual. However, Sterling's Radio Manual does provide both the schematic and the operating instructions for the IP-503 Long Wave Loading Unit in both the 1st and the 2nd editions.

Schematic for the IP-501 from Bucher's Wireless Equipment

This is the schematic for the Radiomarine version of the IP-501-A. Note that the circuit shown doesn't have the earlier Telephone Condenser switch. The Telephone Condenser switch circuit has been replaced with a simple pi-network low pass filter.

Note in the IP-501-A schematic shown to the left that this is the Radiomarine version without the Telephone Condenser switch. Instead a pi-network Low Pass filter using a 1h choke with a .0015uf and a .002uf capacitors is installed. Additionally, note the 2uf bypass capacitors on the Detector plate and Amp plate voltage inputs. Further differences are that +45vdc is shown for the AF amplifier plates. The manual indicates that if +45vdc is used for the AF amp plates, then the grid C bias -4.5vdc can be replaced by shunting the C- to C+ but if +90vdc is used for the AF amp plates, then -4.5 C bias is required. However, the Wireless Specialty Apparatus version of the IP-501-A had "+90" nomenclature engraved on the front panel for the AF amp plate voltage input. 

Schematic for the SE-1420 from the Instruction Book

Useful Hints for Restoring the SE-1420, IP-501 and IP-501-A Receivers

Synchronizing the Tickler Variometer - The variometer has to increase total inductance with the proper sign which consists of either a sign+ or sign- to indicate the increase or decrease of total inductance as the rotor turns from 0º to 90º to 180º inside the stator coils (stationary tickler L and secondary L extension) as the pointer is advanced up the TICKLER scale (a clockwise rotation.) This results in the receiver requiring higher TICKLER settings as the wavelength is increased (lower frequency.) Reference the schematic for the SE-1420 above. Note that the connections to the Tickler Variometer are numbered. The correct wiring is the detector plate is connected to the stationary Tickler L (#84) as the input. The grid circuit is wired to the secondary L extension coil (#44) to provide the feedback path. The variometer rotor Tickler L output (rotor-front #87) goes to the Circuit Selector Switch, RF pi-filter and on to the audio output and detector B+. The rear rotor connection #86 connects to #85 as a jumper located underneath the Secondary L (hard to see if you don't know it's there.) To check if the variometer is synchronized, place the TICKLER pointer straight up on the scale. Look at the variometer rotor just visible on the shortwave side of the Secondary Inductor and you should be able to see the wire splice-joint that connects the two rotor inductors together in series. If you don't see the splice joint then the rotor is 180º out. Remove the TICKLER knob and pointer, then rotate the variometer rotor so that the splice-joint side is visible, then re-install the knob and pointer with the pointer straight up on the scale (or nearly straight up.) Check the flexible connections on the variometer rotor to make sure they aren't coiled too tight at the extreme of TICKLER adjustment. If the Tickler-Variometer is synchronized as described then the TICKLER pointer will have to be set to higher and higher numbers on the TICKLER scale as the receiver tuned frequency is decreased. For example, tuning around the lower AM-BC will have TICKLER feedback happening around 10 or 20. Tuning in WWVB 60kc will require a TICKLER setting of around 90. This is basically how the IP-501-A manual and the SE-1420 manual describe the TICKLER adjustment.

NOTE 1: Although you do get a change of total inductance up to 90º for maximum and a decrease of inductance with continued rotation of the rotor, the two 90º quadrants in 180º of rotation are shown of opposite sign + or -  to indicate whether the inductance increases with CW rotation or is decreasing with CW rotation. There is a mutual inductance change also. When the variometer is operated in the opposite two 90º quadrants, the receiver might not regenerate on lower frequencies or could possibly oscillate uncontrollably due to improper phase relationships to the grid coils. With the proper variometer synchronizing the receiver's oscillation is controllable on all tuning ranges.

NOTE 2: Some receivers (early SE-1420s) will have the variometer rotor mounted slightly off so that the angle of rotor rotation is not 0-180º. This was probably to allow the TICKLER adjustment to be more "mid-scale." Later receivers have 0-180º rotation and most of the TICKLER action is located in the 0-90º portion of the scale (as would be expected.) This allowed plenty of regeneration at the lowest frequencies that the receiver would tune to since this was about mid-scale (90) on the TICKLER adjustment.

NOTE 3: Sterling's Radio Manual, in the SE-1420 text, mentions that for receiving spark signals (essentially a modulated carrier wave) the TICKLER should be set to about 120º on the scale to prevent oscillations. I can't find this "120º setting" mentioned in the SE-1420 manual or in the IP-501-A manual. There are several setups possible that will allow the TICKLER to regenerate and provide the necessary feedback (within its 90º operational span) on all parts of the 0-180º scale. I set the TICKLER to function as the SE-1420 and the IP-501-A manual indicate and that has the regeneration action between <10º and slightly >90º.

Mechanical Stuff

Dismounting the Primary and Secondary Condensers - The condensers are mounted using 10-32 screws and nuts with stand-offs between the condenser mounting plate and the back of the panel. The nuts are secured by soldering after assembly. To remove either condenser first remove the associated fine adjustment knob and the dial by removing the large knob and collar, then remove the dial. The dial is only held in place with two locating pins and should easily come off. You will now see that the flange that the dial mounted to will just barely fit though the hole in the panel shield. You have to be careful not to bend the shielding too much when removing the condenser otherwise you will end up shorting the condenser to the shield when reinstalling the unit. Unsolder the buss wire connections to the condenser. Then remove the screws and nuts. The soldered nuts will come off easily. Solder is not particularly strong and usually with a open-end wrench on the nut and a large screw driver on the screw head, the solder joint comes loose with minimum effort. You can also heat the joint up with a larger soldering gun or iron and then break the joint loose. Heated solder is even weaker and the screws will loosen with almost no effort. After the screws and nuts are off, carefully rotate the condenser assembly while lifting it off of the panel. You will find some interference between the panel shield and the dial flange but by rotating the assembly, the flange will clear the shield hole. Be sure to check the shield hole for bends - it should be straight and even with the back of the panel. Be sure to keep track of the four stand-offs. Remount in the reverse order.

Dial Pointers - These are rather complex assemblies for the simple job they do. The "lifter" mechanism is located on the associated inductance assembly. The lifter is gear driven by the inductance switch and the lifter itself is attached to a rack gear. Two guides keep the rack's alignment. The lifter has a "L" shaped bakelite piece that the pointer pin is inserted into. The pointer itself is mounted to the front panel by a two-piece cover-guide that is nickel-plated. The cover-guide is mounted to the front panel with four 2-56 round-head machine screws. To remove the pointer just take out the four guide screws, remove the cover-guide pieces and remove the pointer from the lifter by pulling it away from the panel. If you need to work on the lifter mechanism itself, you will have to remove the associated inductance assembly.

Buss Wire Details - Buss wiring changed as production methods evolved. The early contract SE-1420 receivers use a reddish-brown varnished tubing (spaghetti) for insulation. The wiring style for these receivers is very square and the buss wires actually run much longer than necessary. This was for appearance and was typical of the style of wiring at the time. When the IP-501 and IP-501-A were being produced for RCA, the varnished tubing was changed to black. The style of wiring also changed in that the runs are much shorter and though still somewhat square looking, there are some angles and bends that are for better durability or performance rather than appearance. The Radiomarine IP-501-A receivers still use black varnished tubing but more and more the square-look is giving way to more direct connections. Finally, in the 1927 CGR-5A (SE-1420C) the spaghetti is entirely eliminated and enameled buss wire used. When replacing missing buss wire, try to find an interior photo of a comparable receiver for reference. Buss wire was usually 13 gauge tinned-copper, which is impossible to find. I have used 14 gauge and 12 gauge, both work fine, although the 12 gauge is more difficult to work. Before using either size, the wire should be "drawn" - that is stretched by anchoring one end and then pulling the other - hard (you can actually feel the wire stretch doing this.) This straightens the wire and slightly reduces it's diameter. It will make the buss wiring look very straight and professional, although most of the wire will be covered with varnished tubing.

Restoration of the IP-501-A - 1979 to 1984

Back in 1979, I bought this IP-501-A from a ham friend, W7IND(SK,) who had traded a used telephone pole for it. The price of $75 took into consideration the substantial amount of work that was going to be required to restore the set. Back then, with no Internet, all parts had to be advertised for in Radio Age magazine with the hope that one of the many collector-readers might have what you needed and would be willing to sell the part. It wasn't unusual for part locating to take a year or more. The IP-501-A was missing almost all of the buss wiring, it had the incorrect AF transformers, the Telephone Switch was gone along with the correct tube socket assembly. Additionally, the set's front panel was in pretty rough condition as were all of the nickel-plated hardware parts. The cabinet was actually in pretty good condition and the parts that remained were also in good condition.

Restoration No. 1 & No. 2 - My first restoration just got everything cleaned up and looking fairly good but I didn't want the IP-501-A to be just a "shelf queen" so I began to advertise for specific parts I needed to get it operational. That resulted in the second, functional restoration. I used black plastic tubing for the "spaghetti" on the new buss wiring and the interstage transformers were two old Jefferson units. I had to make several parts. I made the tube socket assembly from .25" thick original vintage bakelite. The nickel-plated tube socket shells came from an old TRF battery set. One small knob had to be cast in epoxy resin with black filler so it would come out looking like hard rubber. The metal parts that had to be made were two binding posts and one knob pointer. I got the IP-501-A running and eventually wrote an article on it for Radio Age (April 1984 issue.) Don Patterson (editor for Radio Age) sent me some material on the IP-501-A that included an article written on the IP-501-A receiver back in the 1960s for Popular Electronics. The article had a fair photograph of the inside of an original IP-501-A, something I had never seen before.

Restoration No. 3 - My third restoration was to correct the inaccuracies of the two former attempts and to result in the IP-501-A becoming representative of an original receiver both physically and operationally, based mainly on the Popular Electronics photo. I started to search for more parts for the new, third, restoration. The easiest to find were the two RCA audio interstage transformers. The new buss wire used was now 12 gauge (I had used 14ga. before) which also was easy to find. The lacquered tubing or "spaghetti" was a reproduction product supplied by one of the few dealers then around and doing business.

IP-501-A as I received it before any work was performed - April 12, 1979. This photo shows the deplorable condition that the front panel was in. Since the front panel is hard rubber, it is easy to aggressively clean it with soapy water and 0000 steel wool. It sounds harsh but the panel can take it and this cleaning method removes all of the staining that is usually found on these receivers.

As received April 12, 1979. This photo shows how much was missing inside. Note that most of the buss wire is gone, the non-original tube socket assembly is made out of masonite, the AF transformers are Ferranti units. Luckily, the meter, the filament pot, the phone jacks and the tube socket frame were original parts. See photo in the next section for the restored chassis.

The Telephone Condenser Switch and assembly was rebuilt using newer parts and then installed in a painted black, brass metal box I made to hide the modern parts. All of the hardware on the front panel was removed and then cleaned and re-nickel plated. The tuning dials were listed originally as "German Silver" but that's just a fancy name for heavy nickel plating that has a small amount of copper in the plating anode. In order to have all of the hardware parts match, since some were new repros, I had to re-nickel plate all of the hardware. That way it all matches and looks the same vintage. Disassembly is difficult because all screw and nut assemblies are soldered. The technique for removal is to use the soldering iron to heat the solder and nut, then while the joint is still hot use a nut driver to remove the nut.  While hot, the solder isn't very strong and the nut will back off with very little effort. Clean the screws and nuts before reassembly for better solder flow.

This third restoration was finished late in 1984 and resulted in the IP-501-A looking original and functioning as it should. Or did it? I found that I couldn't get the receiver to oscillate below about 250kc no matter where the TICKLER was set. Reversing the variometer leads got the receiver to oscillate but the wiring layout didn't match photos of original IP-501-A receivers. I finally revised the way I had done the buss wiring which then allowed the variometer stator input to connect to the plate and the front of the variometer rotor to be the output. This got the IP-501-A looking correct inside and working the way it should - able to regenerate down as low as the receiver would tune.  In 2026, a thorough examination revealed some interesting problems, details in the next section.

NOTE: Although there's no way to confirm the supposed provenance, W7IND told me that this IP-501-A had been aboard the S.S. Mariposa. It seemed likely that the receiver had been removed early in WWII when the S.S. Mariposa was converted to a troop carrier ship. A little research turned up that the S.S. Mariposa was owned by the Matson Line shipping company. They had built the Mariposa using a Government Loan that stipulated that during wartime the ship could be used as needed by the War Department, so it was converted to a troop carrier for WWII. That the IP-501-A survived isn't too surprising. Many of the shipyards that removed equipment during retrofits would keep the sellable items to later market them as surplus, post-WWII. After that, the IP-501-A was hamstered a bit but it was basically preserved enough for a complete restoration,...well, maybe a few of them.

Updating the 1984 IP-501-A Restoration in 2026 - A Lot More Work Than I Thought it Would Be!

This update all started when I tried to use the IP-503 Long Wave Loading Unit with this WSA IP-501-A. The receiver wouldn't go into oscillation when the IP-503 was switched in. Experimentation that reversed the connections to the LW Tickler resulted in the receiver and LW Loading Unit working together properly. But, the "crossed" wires on the front panel connections wasn't correct and, being OCD, I had to investigate that issue further. After removing the IP-501-A from its cabinet, this is what I found,...

1. LW TICKLER Terminals - These terminals seemed to be reverse connected (but they weren't.) It would be a transparent error when the shunt was installed but would become very obvious when receiver is operated with the IP-503 Long Wave Loading Unit. I've always operated the IP-501-A with the LW TICKLER shunt installed so if there was an error it would have remained unknown. With the acquisition of the IP-503 and operating it with the IP-501-A, the possible reversed tickler wiring would not allow the receiver detector to oscillate, so the error, whatever the cause, now has become important to correct.

2. 1st Audio Interstage Transformer Secondary Bypass Capacitor - This RF suppressor capacitor was not installed. This capacitor installation won't cause any apparent changes. It's a very small amount of capacitance so it really shouldn't affect the audio reproduction since its purpose is just to remove any RF ahead of the Audio Amplifier grid input. This .00025uf capacitor is also present in the SE-1000 and the Triode Type-B amplifiers, so it should be in the WSA versions of the IP-501-A as well.

3. B+ Bypass Capacitors - This is a dual 2mf unit that should be installed on the +45 Detector terminal and on the +45/+90 AF Amp terminal. It might have only been used on Radiomarine versions. Doubtful that any changes would be apparent if I did install these bypass capacitors.

4. TELEPHONE CONDENSER Switch - I built this incorrectly using a modern switch and modern components. It needs to be an actual "replica" of the original. I used a modern rotary switch with 30º spacing and the original switch had 18º spacing. The knob pointer never aligned correctly with the index lines and because of that I always left it in position 4, the only position where the pointer aligned correctly. Electronically performance is okay but the construction and components do need to be checked for correct values. The capacitor values were never specified on older schematics but using the .0015uf and .002uf capacitor values and the 1h choke value (as shown in the Radiomarine schematic) as a guide and checking what the choke is (or if I even used one) will be part of this new, 2026 update of the 1984 restoration.

This photograph is of the "all-original" RMCA IP-501-A receiver that is shown in a section above from "Techno-Gallerie" showing the chassis and wiring in detail. This is just one of four detailed photos that I have of the "Techno-Gallerie" RMCA receiver. This photo shows that the wiring generally appears the same as my 1984 restoration BUT a close look reveals several differences.

In 1984, I think I had a hand-drawn schematic to use but I don't know where that came from. Lack of detailed information at that time probably resulted in the receiver working but not really wired per the detailed information I now have. The information I now have consists of four close-up photos of the interior of an original RMCA IP-501-A, "from the manual" wiring diagrams of the IP-501-A (RMCA version) and the wiring diagram plus "from the manual" assembly drawings of the SE-1420 (for the coil hookups.) I'm hesitant to "dive-in" and rewire a working IP-501-A, BUT I have to remember that this receiver had a "hamster-hacked" interior when I got it back in 1979. I'm sure that these wiring errors that appeared to be original wiring were actually wiring changes that probably dated from the late-1940s or early-1950s. Wiring the receiver per the schematic and wiring diagram is really the only practical solution to all of the conflicts and confusion. Restorations should try to adhere to the official documentation whenever possible.

I must have thought that I'd never have to remove the TELEPHONE CONDENSER switch since I have the three connecting buss wires exiting out holes in the metal box rather than having terminals on the box that would allow easy extraction. I'm going to have to unsolder the buss wires at their end connections to remove the metal box. From there I can rebuild the TELEPHONE CONDENSER switch as a functional "replica" or, at least, as close to that as is practical.

This is a 2026 photograph of my WSA IP-501-A before I made any changes to the wiring. As can be seen in a comparison with the original RMCA IP-501-A shown above, the wiring appears very similar. However, subtle differences are causing conflicts with the IP-503, described in the text.

The .00025uf bypass capacitor will have to be installed on the interstage transformer terminals rather than across the buss wires. The same WSA caveat applies but this bypass capacitor was used on the SE-1000 and the Triode Type-B amplifiers that were contemporaries of the WSA IP-501-A so it should be installed.

1. Coupling Coil connections had one end going to GND which is correct. The other end was wired directly to the Secondary Inductance switch arm, which is incorrect. The "other end" of the Coupling Coil should be connected to the left SEC LOAD terminal. This required making a new buss wire with black lacquer sleeving that was bent to fit first, checked for fit and then installed and soldered.

2. The right side SEC LOAD terminal was connected to the Secondary Inductor end terminal. The right side SEC LOAD terminal should be connected to the Secondary Inductance switch arm. That places the LW SEC LOAD terminals between the output of the Coupling Coil and the input to the Secondary Inductance. I was able to utilize the existing buss wire for the right side terminal to switch arm connection.

3. Secondary Inductance end terminal was wired to the right side LW TICKLER terminal and an additional wire was connected to the Detector Plate. The Secondary Inductance end terminal should be routed to the rotor of the Secondary Tuning Condenser (also connected to the Function switch then to B-/A+.) This required a new buss wire with black lacquer sleeving to make the connection.

Quickie Test - At this point I wanted to confirm that the IP-501-A was going to function correctly so it was moved from the work bench to the operating table where I could connect the voltage input cable wires, connect the antenna and ground along with connecting the WE 10-D horn speaker. Upon power-up, the IP-501-A was tuned approximately to 630kc and KPLY from Reno was quite strong as was the feedback. A few adjustments and everything was working correctly. I tuned down to 100kc (3000 meters) for the Loran-E signal and then down to 60kc (5000 meters) for WWVB to confirm that the IP-501-A did regenerate on all tunable frequencies. The chassis wasn't installed in the cabinet so no shielding for this testing.

4. Although the IP-501-A seemed to work correctly, the TICKLER regeneration seemed backwards because I would have to decrease the TICKLER control as the frequency decreased. That's the opposite of the standard setup. The TICKLER can be setup two ways. One, per the manual, has the regeneration control setting increasing as the frequency decreases but able to achieve oscillation on all frequencies. The second method requires the TICKLER to be setup 180º opposite of the manual setup. However, this setup has the TICKLER control being reduced as the frequency is decreased. Maybe it's just preference of operation since both ways do work but I prefer the setup from the manual. In the manual setup, the TICKLER is increased as the frequency tuned is decreased.

5. The bypass capacitor on the 1st AF Amplifier Grid wasn't installed. I suspect that this capacitor was necessary to prevent RF from the ship's transmitter getting into the audio amplifier stages. The value is so low at 250pf (.00025uf) that it can only be for RF suppression. It's unlikely that RF from the oscillating detector would make it to the secondary winding of the interstage transformer so the likely function was preventing transmitter RF from leaking into the receiver audio circuitry where it would eventually make it to the radio op's 'phones. If the transmitter was the typical 2KW quenched gap spark type, then the RF would be modulated and audible if it leaked into the audio section of the receiver. As expected, no auditory difference with the addition of this component (I used a 500pf,...the only value I had that was the proper vintage, unfortunately the capacitor wasn't a Faradon brand.) NOTE: Although there's a SEND position on the Function Switch, most ship radio stations operated split-frequency, transmitting on one frequency and listening on another. Most of the time the receivers weren't completely disabled during transmit.

6. The dual B+ voltage input bypass capacitor to B- was to compensate for aging B batteries. As the B batteries aged the voltage became less but the battery's internal resistance increased. This high internal resistance could cause swings in the audio circuits when the varying current load from the audio demands decreased the B voltage. Sometimes this caused "motor-boating" that was a low-frequency audio oscillation. The bypass capacitors on the +45vdc and the +90vdc lowered the impedance of the voltage inputs but didn't have any effect on the DC voltage. This shunted any low frequency oscillations to B-. Installing these bypass capacitors isn't something that is instantly apparent, especially when using a B-eliminator as the voltage source since that voltage source is a constant impedance and doesn't change. However, I've added two 1uf 200v paper capacitors from the +45vdc and the +90vdc terminals to B-/A+ just to be somewhat authentic (maybe.) Even though these B+ bypass capacitors weren't used in the SE-1420 receiver, it seems probable that the WSA version of the IP-501-A had these bypass capacitors. I don't have an original photo or artwork showing what they looked like or even if they existed in early receivers. The capacitors I installed were Aerovox brand and, while not particularly vintage, did have the appearance of a couple of vintage components. They can easily be removed if I ever find confirmation that they shouldn't be installed in WSA versions of the IP-501-A.

Another Quickie Test - I needed to install the IP-501-A into its cabinet (for full shielding) and interconnect the IP-503 to verify correct operation of these two units together. The IP-501-A now has the IP-503 connected in the standard manner and everything works fine. I believe that rather than the TICKLER being the problem, it was the Secondary Inductance extension L not being wired correctly along with the SEC LOAD terminals wired incorrectly. Everything is now wired per the manuals for the IP-501-A and the SE-1420. The SE-1420 schematic actually has numbers for the connections to the Secondary Inductor and the Tickler variometer. It makes confirming connections much easier.

7. Telephone Condenser Switch - I've found a six-position vintage tap switch with separate detents. I'd have to harvest this switch from a parts set but because it's a parts set, I'd have two of these switches. If it works well for the IP-501-A Telephone Condenser switch, I might consider using the second switch in rebuilding the SE-1420 Telephone Condenser switch. More details when I've determined that this switch can successfully be adapted and used as a replica Telephone Condenser switch. UPDATE: I measured the switching angle at 15º and that would be okay except the switch layout is enormous. 3.25" x 3.0" required space but the original Telephone Condenser switch fits into an area of about 2.25" x 2.0" - I'm going to have to salvage the parts of this switch and build a Telephone Condenser switch using those parts that will fit into the space available but still have the correct feel to the operation.

8. Tube Socket Platform Spring-Suspension - I did add the cotton-wadding to the interior of the eight springs that suspend the tube socket platform. What I used was similar to cotton felt but less dense. Easy to push in and looks correct. 

Restoration of the SE-1420B  -  1990 to 2009

I bought this SE-1420B from a fellow in Louisiana who had advertised it in Antique Radio Classified magazine in 1990. He had listed the radio as a "Radiomarine Corp Receiver." I was curious as to what it was so I called and asked him to describe the receiver to me. When I heard "...,two large metal dials, lots of metal binding posts and an oak cabinet...," I was sure it was an IP-501 receiver. The price of $150 plus shipping took into consideration that the receiver was nowhere near complete and had been extensively modified by someone, circa 1940s. Since this was long before the Internet got going and before the capability of immediate texting of photos, the seller had to verbally describe over the telephone all of the modifications and indicated that no major holes were drilled and the coils and condensers were present. When the SE-1420B arrived I found he had described it very accurately (that was the norm, then.) The most important parts to have present on these types of receivers are all of the coils, condensers, bandswitches, dials and cabinet. Most of the other parts can be found or replicated. It seems to be common to find these types of receivers with most or all of the buss wiring missing. Also, many times they are found with conversions to later vintage tubes. Most of the time this is the work of "hamsters" (radio amateurs who are all too eager to modify vintage equipment into something it was never intended to be.) The SE-1420 family was available surplus perhaps as early as the late-thirties and certainly by the post-WWII era. Most of the modifications seem to date from that time period.

This SE-1420B had all of the essential parts so now I just had to find all of the missing parts. First on the list was a buzzer which was easily found, though it's a Federal T&T type SC BZ-1 (Signal Corps) which is not the original make. I made a replica buzzer switch. Next, I needed a suitable meter. Although a CAY-2601 ammeter meter is correct for this vintage SE-1420, I was only able to find a similar vintage Weston DC Voltmeter with 5vdc high-lighted in red. It's not technically correct but probably imparts better information when actually operating the receiver (besides, later SE-1420s had filament voltmeters and probably those receivers updated by the military also had DC voltmeters installed.) Two metal pointers had to be made and two replica knobs cast. The tube access door was missing its knob but a very similar brass type was found at the hardware store, although I had to nickel plate it. A Federal T&T low-capacitance lever switch was found on the Internet (probably after I had owned this receiver for at least 12 years.) 

Replicating the SE-1420 Tube Socket
The early versions of the SE1420 have a complex, spring suspension tube socket mounted on long standoffs. Later versions eliminated this over-designed, expensive-to-build socket with a simple spring-suspended bakelite platform and standard bayonet-twist type socket. Of course, this much easier solution to the missing tube socket was tempting but my OCD-nature prompted the construction of an accurate replica of the original-type tube socket. The original and elaborate suspension socket has an incredible 77 total parts to the assembly, including 12 conical springs and dozens of nuts, washers and screws, not to mention the three mounting rings that hold everything together. There are 21 parts just in the three standoffs that mount the socket to the panel. I delayed restoring the SE-1420 beyond "shelf queen" for almost twenty years, mainly because of the difficulty in replicating this original-type socket due to a lack of detailed information. Over the past several years, I collected various vintage photos that showed the elaborate spring socket from various angles. Finally, in 2009, I had enough information (and interest) to go ahead with building a replica spring socket (and hopefully completing the SE-1420 restoration.) Building any multi-part assembly is certainly made more difficult when a physical example is not available to examine and measure, or a detailed mechanical drawing doesn't exist. Using five vintage photos as the reference, I was able to use proportional measuring to determine the size of the various parts that comprised the tube socket. This method involves measuring existing parts from my SE-1420 and then measuring the same parts in the photos to determine scale and then extrapolating what the measurements of the socket parts should be. I created several scale and non-scale drawings to "figure out" how this over-designed mechanism was going to work.

77 parts are required for the Tube Socket. If you're OCD-enough to count the parts shown in the photo, you'll notice that the lugs and the lug spacers aren't shown. Also, the tube socket is already somewhat assembled. The metal base plate, the stainless mounting studs, the thick brass spacers and the shouldered screws were made by a machinist. I made the bakelite parts.

I had a local machinist make the standoffs, the shouldered screws and the metal base plate based upon my drawings. I made all of the bakelite pieces and the tube contact pieces. The socket shell and tube pin contacts were from a 1920s battery radio and were found in the junk box. Assembly was fitted together to check everything and then, when I was sure of a proper fit, the brass screws and nuts were soldered. This duplicated what was normally found in shipboard receivers and was done to prevent assemblies from shaking loose during the constant vibration encountered while at sea. I had to fit brass spacers (like thick washers) inside the springs to keep them centered. From the vintage photos, it appeared that the main support springs had extension spacers. I soldered brass extension spacers to the springs where necessary. The bakelite wire carrier ring has rubber insulated wire connections coming from the tube pin contact strips. These were routed as seen in the vintage photographs.

UPDATE 2026: With excellent condition, original SE-1420 receivers showing up on eBay once in a while, I've now seen some excellent photographs of original-type spring-suspension tube sockets. My replica is pretty close in appearance and functionality (considering I built it 17 years ago.) Of course, nickel-plating the springs and other brass parts should have been done. I should have used non-threaded rods for the spring-suspension assemblies. The three main support rods should have been made out of brass, nickel-plated and then brass nuts used for installation followed by soldering the nuts (I used stainless steel for the rods and nuts - bummer.) Original examples have cotton wadding pushed into the springs (I've installed the cotton wadding.) But, other than those minor points, the 77 piece replica socket looks pretty much like an original. See photo to the right for the assembled tube socket before it was installed into the SE-1420 and the photo below for a 2026 look.

The inside of the Telephone Condenser Switch showing the contacts, capacitors and choke.

The replica tube socket close-up. Note the cotton wadding inside the conical springs. Also, note the non-original Grid Leak. 201A tube installed.  2026 photo

"Patina" is a very important part of replicating old parts. I deliberately left the washing residue on the tube socket and also judiciously added scratches and marring to the TC switch box paint. I used a chemical "patina" to darken solder joints and to darken the brass parts of the tube socket. This imparts the impression that one is looking at original parts, original soldering,...a true vintage replication.

I did install one upgrade to the SE-1420 and that was a grid-leak to improve performance with 201A tubes. This was a common upgrade done by the military in the early-twenties as vacuum tube performance evolved and improved. Originally, the SE-1420 didn't have a grid capacitor or resistor and relied on the negative bias to properly act as a detector. This setup was difficult to adjust since the plate voltage and the filament voltage needed to be carefully adjusted for maximum detector performance. The grid-leak detector circuit didn't require any special adjustments. I mounted the grid-leak assembly where it was typically mounted in the BC-131,...on the Secondary coil mount next to the tube socket (see photo to the left.)

Cabinet Restoration
The top of the SE-1420 cabinet was severely water damaged. The oak wood was almost rotten and all of the original finish was gone long ago. Fortunately the bottom still had some original finish left for matching the color. The early SE-1420 cabinets are darker than the later IP-501 receivers. The good finish on the bottom was about the color of "iced tea." I had to remove a lot of damaged wood from the top by heavy sanding. This damaged wood was soft and came off like coarse wood fibers until I finally got down to undamaged wood. There were many, many holes drilled in the case over the years. I filled these with wood filler. The rest of the case was in good shape and only needed minor touch-up. After one coat of finish, I touched up all of the "filled holes" with artist's acrylic mixed to match the finished color. This way grain can be painted in on the filled holes and they will blend in with the rest of the wood. I finished the case in amber shellac and boiled linseed oil. That certainly wasn't original but it can easily be removed if I ever do find out what was used as the original finish. I suspect that, given the time period and the intended marine environment, spar varnish would have been used.

Updating and Correcting the 2009 Restoration - The SE-1420B Goes Back to the Workbench in 2026

1. GND terminal, panel shielding and grounding condenser are not connected per the manual.
2. A+ and B- are connected directly to the panel shield with lots of solder. The front panel GND terminal appears to be connected by way of the grounding condenser to the panel shield/A+B-.
3. The TICKLER coil doesn't appear to be wired correctly - at least, not as shown in the detailed drawings in the SE-1420 manual.
4. The Primary Inductor switch has position A wired directly to the switch arm.
5. The Buzzer coupler is a brass tube with the buss wire going through it. Schematic, assembly drawings and photos of original receivers all show the bare wire coil type of coupler.
6. When the SE-1420 is out of the cabinet, I want to install the cotton wadding into the conical springs of the tube socket. The installation of the cotton wadding as spring-padding really helps stabilize and limit the movement of the tube socket.

These problems are just the obvious problems that can be spotted looking at the photographs. I'm sure there are several other problems that will become apparent when the SE-1420 is out of the cabinet.

SE-1420 Out of the Cabinet and on the Workbench - Sept. 22, 2026

2026 Plans for Correction - The plan is to correct all of the obvious conflicts between the SE-1420 documentation (1919 manual) and this receiver. However, certain things can't be put back to original. For instance, the Filament Control Rheostat and the Filament DCV meter. The original construction used tapped Rheostat that allowed a negative bias on the detector tube. Also, the CAY-2601 "live-zero" current meter that was to function with earlier tube types that specified filament current rather than voltage. The "2026 Plan" will be to correct the problems with the Primary Inductor, the shield connected A+/B-, the grounding condenser wiring, the Buzzer coupling non-original brass sleeve, the GND terminal connection, possible TICKLER connection issues and any other conflicts with the SE-1420 documentation. The "exception for correction" is going to be how the Filament circuit is set up. I'm going to leave the wiring of the Filament circuit as if the SE-1420 had been modified in the mid-1920s to use 201A tubes and have the detector operate with a Grid-Leak RC. In that case, the original tapped Fil Rheostat would have been replaced, the CAY-2601 meter would have been replaced with a DCV meter and the Grid Leak RC added. If I had the original SE-1420 components, I would return the Filament circuit to original and remove the grid leak also. This would require using a UV-200 tube (or perhaps a Moorhead tube) since the filament current required for these tubes is much higher than the .25A necessary for the 201A. I think the most serious conflict at present is the way that A+/B- are directly connected to the front panel shield and the GND connector isn't directly connected to the front panel shield. Essentially, the shield is capacitively-coupled to the A+/B- that is grounded BUT the GND terminal is essentially floating (at DC anyway.) The Primary L switch wiring is also a serious error. 

Rework Performed on the SE-1420 - Sept 22-25, 2026

1. A+/B- Error - Unsoldered the buss wires going to the A+ and B- terminals and then unsoldered and removed the large copper washers on the A+ and B- terminals that were soldered directly to the front panel shield. Cleaned off all of the solder on the shield area. I installed fiber insulating washers with a brass washer on top then the 6-32 brass nut was threaded back in place. One terminal required some thread chasing and the nut needed to have the threads chased with a tap to remove some excess solder. The A+ and B- terminals were then reassembled and the buss wires soldered back in place. This completed the rework necessary on the A+ and B- terminals to isolate them from the front panel shield. In moving the buss wires, two of the solder joints broke loose on the Detector selector switch and had to be soldered back in place.  NOTE: I just can't believe that I actually was the "hamster" that perpetrated this error. It's so obvious, I just don't know where I got the idea that the A+B- should be directly grounded to the panel shield. That's not shown on any SE-1420 schematic. I think that at the time I assumed that the aged patina of the wiring indicated it was original even though it blatantly contradicted what was shown on schematics. I never thought about modifications from the 1940s being responsible. Oh well,...at least I'm correcting the problem now.
 

2. GND, Panel Shield and Primary Condenser Errors - Buss wire removed from the ground side of the static gap. Removed the buss wire that connected the "ungrounded" GND terminal to the Grounding Condenser. Cleaned the area around the GND terminal and then placed a large "solder bridge" from the GND terminal to the shield (a solder bridge is how the GND to shield connection appears in the photographs of original SE-1420 receivers.) The buss wire that was on the GND terminal was now routed to the ground side of the static gap. The Primary Condenser rotor was connected to the ground side of the Grounding Condenser which is correct (although the GND was floating.) I connected a buss wire from the ground side of the Grounding Condenser to the Buzzer connection that runs to the shield-ground. This has the Primary Condenser rotor connected to the panel shield, which is correct (it had been connected to A+/B-.) The Grounding Condenser is now connected from the Coupling coil buss wire to shield ground, which is correct. I checked with a VOM to make sure the A+ and B- were isolated from the shield and that the GND terminal (at the front of the terminal) was connected to the panel shield.    NOTE: These were other wiring errors that I installed. I don't know what kind of documentation I was using,...probably my imagination. 3. Primary Inductance Switch, Buzzer Coupler Errors, Cotton Wadding - Removed the buss wire connecting the Primary Inductance switch position A to the switch arm. The installation of this buss wire was done many decades ago, it's not original solder but it was old-looking solder. The installation compromised the Litz wire coming from the Inductor as it was only attached with a couple of strands of wire. I had to recondition the wire end and then solder it back in position. The brass sleeve over the Antenna buss wire is very old and a nicely-made piece, but I can't find documentation anywhere that a brass tube was used as a Buzzer coupler. I removed the brass tube and installed the standard wire coil Buzzer coupler. I'll save the brass tube in case I find out later that it was original,...doubtful, but possible.    NOTE: At least these were existing errors installed by some former owner.   I installed cotton wadding, like felt but not as dense, into the conical springs of the tube socket. I used a small right-angle awl-type tool to push the wadding into the springs. This greatly improved the stability of the tube socket and wadding was originally installed into all of the tube socket spring suspensions. Photo to the right shows the GND terminal, panel shield, Grounding Condenser hookups, the proper Buzzer coupler and the Primary L switch corrections installed.

4. Quickie Test on the Workbench - Lots of contact problems. I can tell this receiver hasn't been in operation since 2009. DeOxit was applied with a small paint brush to all of the contacts surfaces on the Primary and Secondary Inductance switches. The bushings were also given the DeOxit treatment. The Primary and Secondary Condensers were also given the DeOxit treatment on the rotor contact surfaces. This DeOxit treatment was a MAJOR improvement in the stability of the receiver's performance. However, being out of the cabinet and with no real shielding, the regeneration is very touchy on the highest frequencies, AM-BC. I had to install the receiver into its cabinet to provide the shielding necessary to stabilize the regeneration. As mentioned in the manual, using the TELEPHONE CONDENSER switch to select different plate loads will vary to some extent where the regeneration peak happens on the TICKLER scale. Lower numbers (more C) helps the lower frequencies while high numbers help the higher frequencies. Regeneration is adjustable from the lowest frequencies up to the top frequency coverage. Incidentally, this particular SE-1420 tunes up to about 1400kc (215 meters.)

5. Operation with the two-stage AF Amplifier - The connection of the TELEPHONES terminals to the D-A only requires observing that on the SE-1420 the upper TELEPHONES terminal connects to the tickler inside the SE-1420. This terminal is then wired to the D-A TICK lower terminal and that connects to the primary winding of the first interstage transformer, specifically to the "P" (plate) terminal. Then the SE-1420 lower TELEPHONES terminal, which is connected to B+ inside the SE-1420, is wired to the DET B+ terminal on the D-A which, inside the D-A, connects to the "B" terminal on the primary winding of the first interstage transformer. All vintage audio amplifiers connect in the same manner with the same observations of where the terminals actually go to in both circuits. Additionally, on the D-A, AMP B+ is connected to +90vdc, A+ to A+/B- and A- to A-. The SE-1420 will already have it operational voltages connected. The -4.5vdc C bias for the D-A is connected to the fahnstock clips for grid negative bias (necessary when operating the amplifier plates at +90vdc.)

I used Baldwin Type-C 'phones for the audio output (connected to the phone jack on the D-A.) Any of the local AM-BC stations can be deafening. Always keep the phones on the cheekbones far in front of the ears. About the only control of the sensitivity is either the TICKER or the COUPLING but it's also possible to detune the Primary Condenser on LOUD stations. Of course, this setup would easily drive a horn speaker to room volume. I also checked WWVB 60kc and that was a strong signal as was Loran-E on 100kc. A very strong MSK signal on 76.0kc was identified as a DARC subcarrier type for a utility FM transmission of some type of data (unknown, but strong.) As mentioned above, the use of the TELEPHONE CONDENSER switch for providing a selectable plate load on the detector tube is essential for attaining proper feedback over the entire tuning range.

Performance Testing 100 year old Shipboard Radio Receivers
 

Operating the SE-1420B

The SE-1420B during testing. The receiver is on (note filament meter) also filaments of the 201A tubes can be seen. The Pilot Radio Redi-Blox single stage AF amplifier is on the right. The receiver is tuned to PBT 338kc (as seen on the frequency counter.) PBT 338kc (called Proberta) was located in Red Bluff, California,...decommissioned in 2012.   photo date: Feb 2009

The initial test was on the AM BC band since signals there are very strong. As soon as the voltage was applied the SE-1420 started to "squeal" through the earphones - a really good sign for regenerative receivers. Backing the TICKLER down brought in the local (Reno) AM BC station on 920kc. A slight tuning of the Antenna Condenser had that station coming in strong in the "Baldie" earphones. I tuned in a few more AM BC stations with very good results, so now it was time to try "NO", the non-directional beacon (on 351kc) at Reno-Tahoe International Airport. Switching to tuning range to "2" and Antenna Tuning to "3", "NO" was found quickly. Since NDBs send MCW signals, the signals are easier to find if the detector is oscillating. In this mode, the Coupling is more critical and most controls interact significantly. Stability is also very difficult to achieve but the SE-1420 seemed to be fairly stable with a UX-201A tube. This isn't the tube type that was normally used with these early-version receivers but this was just a test of operation.

The next step was to try the Western Electric VT-1 and then the Moorhead ER, both typical tubes used with the SE-1420 back in 1920 or so. The WE VT-1 works very similar to the 201A tube except the filament voltage is 3.0vdc. The TICKLER settings and the condenser settings are very close to that of the 201A. This indicates that the WE VT-1 has similar inter-electrode capacitance to the 201A tube. Not so for the Moorhead ER. This tube runs about 4.0vdc on it's pure tungsten filament. TICKLER has to be advanced significantly and even though it is sensitive enough, it is difficult to tell when the tube is oscillating. Again, this is an indication of the different inter-electrode capacitance specifications for the Moorhead ER when compared to the 201A.

In two listening sessions in February 2009, 50 NDBs were received including one newly heard 25W NDB, PA 396kc in Snohomish, Washington.

Incredible performance from a 1920 regenerative receiver.
 

2026 NOTE:  I performed this SE-1420B testing described above while living in Virginia City, Nevada. It would be interesting to retest the SE-1420 now, 17 years later, here in Dayton Valley, Nevada, this time using the "D-A" I built. The "D-A" is a Regenerative Detector and two-stage Audio Amplifier but can be connected to just use the two-stage Audio Amp. The audio gain difference would be a gain of 30 using the Pilot Redi-Blox and a gain of 900 using the "D-A." That should boost the weaker signals,...maybe the noise too. Of course, there will be far fewer NDBs transmitting but there are other LF signals that I didn't test back in 2009. This testing will be conducted in the Fall when LW conditions are beginning to improve. UPDATE - Sept 25, 2026: The SE-1420B has gone back to the workbench after 17 years. The SE-1420B receiver had several serious wiring problems. After the correction of these problems, the SE-1420B is now functioning better than it ever has. Much better stability and ease of operation. The Two-Stages of Audio Amplification really helps, too. LW Reception Test 2026-2027 Season  - Shown in the photo to the right is the SE-1420B with the D-A on top acting as the two-stage Audio Amplifier. Baldwin Type-C 'phones also on top of the receiver. The power source is the old homebrew ABC eliminator that uses active regulators that are actually pretty noisy for operating these types of DC voltage-powered receivers. The ABC eliminator is on the floor below with the harness providing the connections. The Atlas Horn Speaker can be used but for the really weak NDB signals, I have to use the Baldwin 'phones. Instead of a DFC readout for frequency like I used in 2009, if I need to confirm the frequency to identify a station, I now use the HP-3312A Function Generator with its DFC as a heterodyne oscillator (like a heterodyne frequency meter with a digital readout) and zero-beat the received station to confirm its operating frequency. This was how I confirmed that I was actually receiving ALS162 on 162kc. Since ALS162 is a Phase Encoded Time Signal with no over-the-air identification I had to tune the MSK-sounding signal, then zero-beat with the HP-3312A to confirm the signal received was on 162kc exactly. Since ALS162 is running 800KW and is located in Allouis, France it's not a very loud signal (at 1600hrs here) but the signal's sound characteristics plus knowing the exact frequency confirms that it was ALS162. Many of the LF stations below 200kc have to be identified in this manner.

SE-1420B with Two-Stage AF Amp LW Test Set-up for 2026

Long Wave Reception Log for 2026-2027 Season
SE-1420 Receiver with Two-Stage Audio Amplifier

Sept 27, 2026  0543hrs to 0603hrs PDT

MOG 404kc - Montegue, CA
SX 367kc - Cranbrook, BC, CAN
SGX 347kc - Shelby, MT (formerly SBX*)
DC 326kc - Princeton, BC, CAN

JJY 40kc - Mt. Otakadoya, Japan

Copied ALS162 on 162kc, 800KW Phase Encoded Time Signal from Allouis, France on Sept 26, 2026 at 1600hrs PDT

Conditions okay. Intermittent QRN issues not bad this morning. Using homebrew ABC eliminator that is fairly noisy. 250' end-fed wire antenna. Baldwin 'phones.

Total = 4 NDB stations, 1 LF station

*SBX was formally decommissioned in 2017 but it continues intermittent operation using callsigns SGX (currently,) or SDX or UDX.

Operating the IP-501-A

The WSA IP-501-A LW testing 2009. The receiver is on (note the filament meter) and is receiving local NDB, "NO" Reno-Tahoe Int'l AP on 351kc (as seen on the DFC.) NO was the last operating NDB in Nevada,...decommissioned in 2013.    photo date: Feb 2009

Tuning In NDBs - Setting "Critical Coupling"
To receive NDBs, the receiver should be operated as an Autodyne detector. The stations can be roughly located and tuned using the Wavelength Scale on the SECONDARY CONDENSER dial and then using the ANTENNA CONDENSER to tune for maximum signal response. Adjust the TICKLER until you hear the detector go into oscillation. Use just the SECONDARY CONDENSER for station tuning and the ANTENNA CONDENSER to peak the signal. When "peaking" the ANTENNA CONDENSER, as you approach resonance you will hear a couple of loud clicks, a change in received frequency and the detector may stop oscillating. This is a result of too tight of coupling (COUPLING set too high.) Set the COUPLING lower on its scale and again tune through resonance with the ANTENNA CONDENSER. As the ANTENNA CONDENSER is tuned back and forth through resonance, listen to the clicks while reducing COUPLING. At "Critical Coupling" the clicks will stop and the detector will remain in oscillation. Tight coupling will over-drive the detector at resonance, causing the jump in and out of oscillation. The "Critical Coupling" setting is good for a fairly wide tuning range, usually at least 20 to 30kc. The TICKLER setting and the COUPLING setting do interact, so usually just the TICKLER is slightly adjusted when the detector drops out of oscillation. After "Critical Coupling" is set, adjustments to the TICKLER are very slight changes. Most tuning can be done using just the two main tuning controls, SECONDARY CONDENSER for tuning stations and peak with the ANTENNA CONDENSER, along with very slight adjustments of the TICKLER. As the ANTENNA CONDENSER is resonated, you will find that the received frequency changes slightly. This is normal interaction of the autodyne detector. Just slight readjustment of the SECONDARY CONDENSER is necessary for proper tuning. It would be next to impossible to find the weak NDB signals without the receiver set as an autodyne detector. This provides a heterodyne action so the carrier of the MCW NDB signal can be easily heard. Tune to "zero beat" and you hear the MCW signal of the NDB - or maybe two or three NDBs, as there are usually several NDBs assigned to each particular frequency (well, there used to be anyway.)

Tuning for AM BC Operation
The same basic set ups are used for receiving AM signals but the detector must be operated as a straight regenerative detector (not oscillating.) The best sensitivity in a regenerative detector occurs just before the oscillation point. COUPLING is not a critical adjustment in this set-up and, though the COUPLING can be set somewhat tighter (higher on the scale) for AM, it's not really necessary. Anywhere from 45 to 100 is good for AM-BC. Set the TICKLER so that you can hear background noise coming in but not so it is oscillating. Tune around and find an AM station. Peak the signal with the ANTENNA CONDENSER and then adjust the TICKLER to just before the detector breaks into oscillation. The receiver is now operating with maximum sensitivity. Operated as a straight regenerative detector (non-oscillating) there is very little interaction between the controls. You have to keep the two main tuning controls in adjustment as you search around for different stations. The TICKLER doesn't need to be adjusted too much unless you find a really weak AM station you want to listen to.
 
Other LW Stations
Besides AM BC above 500kc and NDBs below, there are several other interesting signals below 500kc. LW BC stations in Europe and Asia can sometimes be received. Radio Rossii at 279kc on Sakhalin Island was very strong in the West and could be received easily during the winter mornings before 6AM PST. Unfortunately, Radio Rossii 279kc is long gone (Russia shut down all of their LW BC stations in January 2014. As of  June 2026, BBC-4 LW-BC shut down. There are currently, in 2026, two Polish LW-BC stations operating and one LW-BC in Algiers. One in Romania and one in Mongolia operate intermittently. The future of all LW-BC is tenuous.) Also, the were "Lowfers" that used to operate 1 watt CW transmitters to 50 ft antennas located in the 190kc to 160kc region of the spectrum - no license was required (I've never heard any of the "Lowfers" and that was probably the intent of the regulations. However, hams now have 630M and 2200M bands, CW and data modes only. Unfortunately, CW-Morse is a rarity on 630M with most transmissions being computer assisted beacon data types with online reception logs that require special equipment and programs for the setups - WSPR mode.) Also, WWVB at 60kc, JJY (Japan's equivalent to WWVB) at 40kc and Loran C (Loran E now) stations at 100kc (Loran C shut down in 2010. Replaced with Loran-E in 2024 running 400KW on 100kc.) Recently, ALS162 was created from one of France's retired LW-BC stations. It's a phase-encoded time signal running 800KW on 162kc. It's fairly easy to receive in the early evenings in the Western USA. Most casual listeners don't receive much of what is on the air below 500kc because they listen for AM/voice signals. Very few AM/voice signals will be encountered below 500kc. Almost everything is data transmissions that are being sent in CW, MCW, various types of data-encoded signals, Pulse-encoded signals, Phase-encoded signals, encrypted very narrow-shift MSK USN signals, etc. Voice is only encountered in LW BC (essentially gone) and very rarely Voice Weather TWEB associated with a very few NDBs (usually Alaskan but I haven't heard any TWEB NDBs in several years.) To receive most data transmissions you must have the detector oscillating so a heterodyne action allows you to actually hear the signals. Once you listen with the autodyne detector or a heterodyne oscillator, you'll be surprised just how many signals there are below 500kc.

Series versus Parallel Antenna Tuning with the IP-501-A
The IP-501-A standard Antenna connection has the Antenna Tuning LC connected in series. Since all of my 2009 testing of this receiver only went down to 200kc or 1500M, I never even tried receiving at the longest wavelengths the receiver can tune to. As with the SE-143 receiver, there could be an advantage to parallel tuning the Antenna LC at these low frequencies. It's easy to try anyway. For parallel Antenna tuning, connect the antenna lead-in wire to the left terminal of the PRIMARY LOAD, leaving the shunt strap connected. Then connect a wire that shorts the ANT terminal to the GND terminal, leaving the GND terminal grounded. Now the IP-501-A Antenna Tuning LC is connected in parallel and that might provide better primary tuning at wavelengths longer than 3000M or 100kc. Interestingly, the Long Wave Loading Unit IP-503, when connected up to the IP-501-A, automatically switches the Antenna Tuning LC to a parallel connection when LONG is selected. Unfortunately, the SE-1420 doesn't provide LF Loading Coil terminals so this type of hook-up can't be implemented for that receiver.
 

Kilocycle to Wavelength in Meters Conversion Chart  - The chart to the right is a very easy way to convert kilocycles to wavelength in meters. ALL of the receivers covered in this two-part write-up have calibrated Secondary Condenser dials,...but that calibration is in wavelength. The changeover to kilocycles from wavelength was ongoing through all of the 1920s and, by 1930, using wavelength on a tuning dial had all but disappeared. So, to use the chart, the first column is kilocycles then "three dots" and then wavelength. For example, if I wanted to tune in the NDB MOG on 405kc, I'd go to 400kc (first column) and see that was equal to 749.6 meters. Tuning the Secondary Condenser dial to 745 meters will certainly be close enough for finding MOG. This chart was in a 1923 Lefax Radio Handbook so the upper frequency limit is just over 2000kc. Optional Digital Frequency Counter Set-up Since the IP-501-A and the SE-1420 use a regenerative detector with only an Antenna Tuner between the detector and the antenna, it is possible to couple a digital frequency counter to the antenna lead-in and then have an accurate frequency read-out. When the receiver's regenerative detector is oscillating it is partially acting as an oscillator and as a detector (autodyne detector.) The oscillator output couples into the antenna tuner and then into the antenna. Many times the old AM BC radios with regenerative detectors would be adjusted to oscillate for picking up weak stations and would then radiate the oscillating from the antenna. The radiated oscillations were considered interference and would be received by the neighbors over their radio receivers in the form of "bloops" and "whistles" that are mentioned in many old radio magazine articles. The regenerative detector's oscillations can be a fairly high amplitude and will easily drive a modern digital frequency counter. Since the detector is oscillating at the received frequency, the counter's display is the frequency that the receiver is tuned to. A simple three foot long wire connected to the counter's input with the other end of the wire wrapped around the antenna lead will couple enough signal into the counter for a read-out. Don't connect the counter ground to anything. This digital frequency read-out will only work when the receiver is oscillating. If the frequency read-out is erratic try increasing the TICKLER slightly for an accurate reading, then reset TICKLER for maximum sensitivity. Sometimes at the detector oscillation point the counter will respond to the detector frequency, the signal modulation and the received noise causing an erratic display. When you are searching for NDBs, it's a big help to know exactly where you are tuned. DFC for the SE-143 Operating as a Regenerative Detector Receiver This method of using a digital frequency counter for a received frequency readout can also be applied to the SE-143 receiver. Since the TICKLER coil is connected to the plate of the detector tube externally on the SE-143, it's easy to wrap about 7 or 8 turns of wire around the TICKLER to detector plate wire as a pick-up. It works a little better if the DFC's ground is connected to A+/B- terminals. Also, as with the SE-1420 and IP-501-A, you have to advance the TICKLER beyond the maximum regeneration/oscillation point or otherwise noise and AM modulation (if present) will cause errors in the readout. Be sure to zero-beat the station's frequency exactly. If the SE-143 is setup to use the SE-1387 and SE-1834 then the detector is non-regenerative. The Heterodyne Oscillator won't provide an accurate frequency indication. I use an accurate function generator with a DFC or a synthesizer signal generator as a frequency marker to determine where the SE-143 and SE-1387/SE-1834 combo is tuned. However, the absolute accuracy of this "marker" setup is compromised by the Heterodyne Oscillator setting. Turn off the HO and modulate the signal generator (400hz modulation) then tune the receiver for maximum,...that should provide the most accurate (carrier) frequency indication.

Kilocycle to Wavelength in Meters Conversion Chart

IP-501-A Testing Results in 2009
During my set-up for test-listening, I pre-set the receiver to around 770M. When power was applied, to my surprise, there was SX 376kc, a Canadian NDB up in Cranbrook, BC (it was only about 4:45PM local time.) That night, during a 30 minute period, I tuned in 25 NDB beacons from 326kc up to about 414kc. Best DX was DDP 391kc in San Juan, Puerto Rico. This is a 2KW transatlantic beacon but it is about 3500 miles from Virginia City, Nevada. Most difficult was probably ULS 395kc, a 25W marker beacon in Ulysses, Kansas. Subsequent sessions have tuned in YMW 366kc in Maniwaki, Quebec, also YY 340kc in Mont Joli, Quebec, both at about 2500 miles and IY 417kc in Charles City, Iowa, a 25W marker beacon. Additionally, Radio Rossii, the LW BC station on 279kc, located on Sakhalin Island was received (shutdown in Jan 2014) along with PN, the NDB at Port Menier, Anticosti Island, Quebec. In the three week period of 1/21 to 2/11, I tuned in over 100 NDBs with the IP-501-A - seven were never-before-heard NDBs. Impressive performance from a (then) 87 year old three-tube regenerative receiver.

IP-501-A NDB Log - Jan 21 to Feb 11, 2009

The following is the log of the NDBs copied using just the IP-501-A receiver and the 135' tuned dipole antenna with the feedline shorted. NDB location, frequency and power (if know) are listed. This reception test was performed in Virginia City, Nevada, my QTH at the time.  Total as of  Feb. 11, '09 was 103. Unfortunately, at this time I didn't list the dates or times for reception, only the station, frequency and location.

* = Newly NDB heard

Long Wave Listening in 2026

IMPORTANT NDB NOTE for 2026: In looking over the 2009 NDB log for the IP-501-A, I'd have to say that nowadays this type of NDB reception is impossible with any type of MW receiver, even modern MW receivers. The sheer number of NDBs that have been decommissioned since 2009 is staggering. None of the USA pilots use NDBs for navigation anymore and that's resulted in most airports having decommissioned their NDB transmitters. Regulations don't require airports to provide non-directional beacon transmissions anymore. In fact, Government regulations encourage Airports to shutdown their NDBs because they are considered an obsolete method of navigation and encourage the use of GPS navigation. The few NDBs still in operation are not used for navigation in the USA. The airport is using the NDB as a voluntary "airport radio identification" signal and the transmissions are kept running to maintain the tradition of  "airport navigation." In addition to NDBs, many of the other traditional aviation navigation signals such as VOLMET (aviation weather reports) are being removed from all parts of the spectrum in the name of "modernization." Airport economics are certainly another factor in the removal of most NDBs, so don't expect these few remaining NDBs to be in operation too much longer,...at least in the USA. Canada is also decommissioning their NDBs at an alarming rate.

New!  2026-27 Long Wave Season Reception Log - Nowadays, in 2026, the IP-501-A is 100+ years old and it hasn't been retested at my new location in Dayton Valley, Nevada. It would be interesting to see how many NDBs could be received 17 years later. I'm sure it will be far fewer NDBs since so many have been decommissioned over the past couple of decades. But there are several other LF signals to check on now that I didn't even try tuning to 17 years ago. In fact, ALS162, an 800KW PE Time signal out of France on 162kc (1800M) wasn't even operating then. Obtaining a rare IP-503 Long Wave Loading Unit in 2026 and then finding that the IP-501-A wouldn't regenerate with the IP-503 connected resulting in the IP-501-A returning to the workbench. Several minor wiring corrections were made to the IP-501-A in Sept. 2026 and the IP-503 LW Loading Unit and the IP-501-A now function together as they should. The new Long Wave Reception Log for 2026-2027 Season will not only have NDBs but many other types of LF and VLF signals received. No DFC monitor this time, I now use an HP-3312A Function Generator and its DFC as a Heterodyne Oscillator (Heterodyne Frequency Meter) to confirm reception tuned frequency for identification because, other than NDBs, very few LW stations actually identify themselves. The first entry is for the first day of the 2026 Autumnal Equinox, September 22, 2026.

IP-501-A and IP-503 ready for LW Season 2026-27

Long Wave Reception Log for 2026-2027 Season
IP-501-A Receiver with IP-503 Long Wave Loading Unit
Fil Supply = Lambda 6vdc 4A  Plate Supply = RCA Duo-Rectron  C-Bias = 3 AA cells in series

Sept 22, 2026  0535hrs to 0555hrs PDT

YQF 320kc - Red Deer, AB, CAN
DC 326kc - Princeton, BC, CAN
RYN 338kc - Tucson, AZ
SBX 347kc - Shelby, MT - sends "SGX"
SX 367kc - Cranbrook, BC, CAN
EX 374kc - Kelowna, BC, CAN
HAU 386kc - Helena, MT
YWB 389kc - West Bank, BC, CAN
MOG 404kc - Montegue, CA

JJY 40kc - Mt. Otakadayo, Japan (PE Time Sig)

Severe QRN for first 10 minutes, then clear with good cndx. IP-503 in SHORT. Using 250' EFW antenna. First day of Autumnal Equinox, start of Long Wave season 2026-2027.

Total = 9 NDB stations, 1 LF station

Sept 24, 2026  0540hrs to 0603hrs PDT

DC 326kc - Princeton, BC, CAN*
LW 257kc - Kelowna, BC, CAN
YCD 251kc - Nanaimo, Vc.Is., BC, CAN
XC 242kc - Cranbrook, BC, CAN

JJY 40kc - Mt. Otakadayo, Japan*

Severe interference from some device sending data every 7 or 8 minutes, lasts about 1 minute, but at 0600hrs RFI was constant. Had about 12 minutes of clear listening between the data burst RFI. Otherwise conditions okay, not as good as 9-22-26 though.

* = Logged in earlier listening session

3 new NDBs - Total NDB stations = 12

Identify the RFI Noise Source First

Check your house - Turn off everything you can in your house and see if the noise goes away. It's amazing, but LED lamps that don't cause any interference above the AM-BC band sometimes cause intense RFI noise below 500kc. Light dimmers are also notorious noise-creators. Wall-wart power supplies, various types of computer accessories, switching power supplies, modern modulated furnace blowers with SCR speed controllers, wireless thermostats, neon pilot lamps,...and just about anything "SMART" including the power company's "SMART power meter" - especially when it's sending data. If just switching off everything in the house doesn't find the culprit then maybe the noise is external to your house. It's common to find that devices that cause no interference at all above 1500kc will create intense RFI below 500kc. Finding RFI sources in your own house is about the easiest type of RFI to eliminate,...or at least identify.

Other External RFI Sources - External noise can be from any of the devices mentioned above but located in your neighbor's house. Modern real estate trends have houses built with virtually no space between houses making the proximity of RFI-creating devices much closer than they were (are) in older neighborhoods. Solar panel "levelers" and "inverters" can be very potent RFI sources. Reports are that the more modern versions of these Solar devices have eliminated the noise,...well,...maybe. "Grow Lamps" are notorious creators of RFI. Older street lamps using Hg-vapor or Na-vapor lamps can be very intense RFI polluters if the lamp is failing and switching on and off. Report the offending street lamp with its ID number to the power company and they will usually come out and replace the failing lamp. Most new street light installations are using LED type lamps and they don't seem to create RFI. With the exception of power company problems, most of the other external RFI sources can't be "fixed" since the "correction" involves cooperation of the offending neighbor which is an unlikely scenario.
 

Coping With Unsolvable RFI Noise Problems

Shielded Magnetic Loop Antennas - If the RFI isn't from your own house then, usually, the listener has to come up with their own solutions to eliminate or, at least, reduce the RFI noise pollution. The most efficient device to use is the Shielded-Magnetic Loop antenna. This type of antenna is very effective at reducing RFI noise. These loops work great on receivers that were built from the mid-1930s and later since the design of these receivers generally used RF transformers as the antenna input circuitry. The Pixel S-M Loop performs quite well below 500kc and can be used (without too much loss) down to 150kc. Depending on the receiver's front-end design, sometimes S-M Loops won't work very well,...especially with early, 1920s receivers. This mainly due to the Primary LC Tuner's series configuration and the Antenna being directly connected to that LC connection. The S-M Loop's 75Z input impedance will have trouble connected directly to the antenna input unless there is some sort of isolation between the loop LNA (low noise amplifier) and the receiver antenna input. To match the S-M Loop to an early receiver use an impedance matching transformer to provide isolation and matching. The 75Z coax connector at the S-M loop LNA should connect to an impedance transformer that has 75Z on one side and Hi-Z (600Z to 1500Z) on the other side. The Hi-Z should have a single terminal for a wire connection. The single wire connects to the ANT terminal of the SE-143. GN terminal to earth ground. These impedance transformers are sold for use with end-fed wire antennas to match the typical Hi-Z of an end-fed wire antenna to a Lo-Z Antenna input of a modern receiver. Many types are available priced from about $25 up to $50. The ratio isn't too critical, I've experimented with two types, one 9:1 that is homebrew and then a End-Fed Wire type that was a 10:1 ratio. Both worked fine for matching the Pixel Loop to a SE-143 or similar type of receiver. Be sure the type purchased has an SO-239 coax fitting for the 75Z and a single terminal stud with wing-nut for the Hi-Z (dual terminal studs will also work with one stud being ANT and the other stud GND.)  NOTE: The Pixel Loop is very expensive at around $900 (spec'd from 30mc to 125kc.) The W6LVP S-M Loop is priced at around $450 (spec'd from 30mc to 130kc.) I've tested and used both of these types of S-M Loop antennas. The Pixel Loop shows some minor signal loss starting around 300kc. The W6LVP Loop shows some minor signal loss starting around 500kc. By 150kc, the signal loss using either loop is quite noticeable. Both of the loops are not new. The Pixel is at least 15 years old and the W6LVP is about 8 years old. Newer examples may perform better (the specs of the W6LVP did change recently to indicate that the 2200M band, 136kc, could be received.)

Antennas and Grounds - In metro-urban areas, with endless sources of high-level EMI/RFI from major industry running 24-7 and millions upon millions of potential consumer RFI creators, listening on MW and LW is going to be impossible. Even an S-M Loop won't solve the RFI problems in metro areas. Going mobile to a rural area, operating on batteries and using a loop antenna is the usual method for LF and MW listening for urban dwellers (kind of like a "camp-out.") Suburban areas are usually relatively quiet but might have an individual RFI noise polluter that can destroy any MW or LF listening with their EM/RFI noise, but usually these sources can be dealt with by using a Shielded-Magnetic Loop operated as described in paragraph above. Shielded-Magnetic Loops DO NOT produce stronger signals even though they employ a low-noise amplifier as part of their design. The Shielded-Magnetic Loop provides a better signal-to-noise ratio due to the antenna being shielded within a non-ferrous metal tube that has a small gap at the bottom of the loop shield tubing. The RFI noise is mainly electrical in nature and is typically vertically polarized. The S-M Loop responds better to the magnetic portion of an electro-magnetic signal and in that sense reduces the noise. But, good results will depend on the receiver having enough gain to take advantage of "not so strong" signals that have an improved signal-to-noise ratio. However, with the 1920s Shipboard receivers, it might be found that the S-M Loop signal just isn't strong enough for real DX reception, even though it's impedance-matched and the noise level is reduced. If that's the case, then another option is the Remotely-tuned Loop. These are homebrew loops that can be fairly large, maybe up to 10' in diameter, with the loop being tuned using varactor diodes (solid-state devices that can change capacitance using an adjustable small bias voltage.) They are easy to build and the pick-up loop (inside the tuned loop's field) can be designed to impedance-match the antenna requirements. Due to the high-Q of the Remotely-tuned Loop, it tends to work rather well in noisy areas. Remotely-tuned Loops generally produce stronger signals than the S-M Loop plus they do have a history of actually being used in the 1920s for direction finding applications (although they didn't use varactor diodes for tuning then.) One has to remember that the 1920s shipboard receivers were designed for a 200' end-fed wire (that is total wire used, the horizontal length plus the vertical drop to the receiver) worked against the expansive metal hull of the ship to provide a ground that was surrounded by a salt-sea environment. It was a really good ground that seeming went on forever. There wasn't a direct-contact submerged ground though. The ship hull's capacitance, Xc, to the sea salt water ground, at RF, was exceptionally high (a very large capacitance value.) In other words, at Radio Frequencies, it was like the hull was in direct contact with the sea. The large antenna, the superb ground, the excellent location (out at sea away from everything) and the 1920s low-RFI noise environment is something that can't be duplicated today.
  

References:

1. Hazeltine, the Professor - by Harold A. Wheeler, SE-1420 origins and history - published in Radio Age, April 1978

2. Radio Manufacturers of the 1920s, Vol 3 -  RCA and Wireless Specialty Apparatus history - by Alan Douglas 1991

3. Westinghouse Type RB, photo of Type RB - by Alan Douglas - published in Radio Age, November 1982

4. Tropical Radio and Telegraph Co., United Fruit Co., National Electrical Supply Co. (NESCO,) International Signaling Co., International Radio Telegraph Co. -  Geo. C. Clark "Radioana," Wikipedia and various other online sources

5. "Keeping the Stars and Strips in the Ether" by Cmdr. Stanford Hooper - RCA-Navy relationship, Creation of RCA by General Electric, Purchase of American Marconi by GE -  from Radio Broadcast - June,1922, - Cmdr. Stanford Hooper and Admiral Bullard were the Navy "Brass" that were sent to General Electric to urge GE to not sell their wireless patents to British Marconi but to form a "Radio Corporation" to keep their wireless patents in American hands.

6. SE-143 Operating Instructions, IP-503 Long Wave Loading Unit - George Sterling's SE-143 section in "The Radio Manual" First Edition actually has quite a bit of information on the SE-143 but be sure to also look at the information on Long Wave loading coils as there's more important information in that section. Also, the IP-503 schematic and instructions are in the 1st and 2nd Editions.

7. IP-501-A Manual, SE-1420 Manual, SE-143 Manual - These manuals are online (free download) at Al Krause's website, www.skywaves.ar88.net  Look under "Communications Receivers - NAVY" - The SE-1420 manual is the Navy Instruction Book and is dated 1919. The IP-501-A manual is dated 1936 and is from RCA and is for the later, Radiomarine version of the receiver. This IP-501-A manual has details on setting "Critical Coupling" that greatly improves MW performance when the detector is oscillating.

8. "The Radio Manual" - by George Sterling, four editions, 1st Ed.-1928, 2nd Ed.-1929, 3rd Ed.-1938, 4th Ed.-1950. 1st Edition has descriptions and operating instructions for SE-143, IP-501/SE-1420, IP-503 Long Wave Loading Unit and information on using LW Loading Coils. The 2nd Edition dropped the SE-143 but has the IP-501/SE-1420. Both the 1st and 2nd Editions included some information and a schematic of the IP-503 Long Wave Loading Unit in the IP-501 section. The IP-501-A isn't covered in any of the Radio Manual editions because Sterling believed that the IP-501/SE-1420 were so similar to the IP-501-A that the information provided was sufficient for radiomen and technicians.

9. "How to Make Commercial Type Radio Apparatus" by Milton B. Sleeper - No. 2 in a series of booklets on radio equipment published in 1922 by The Norman W. Henley Publishing Co., NYC, NY. Excellent artwork for the SE-1420.