Radio Boulevard
Western Historic Radio Museum
 

Shipboard Radio Receiving Equipment
1918 up to 1925

 

   1.  SE-143 - Navy Department - Bureau of Steam Engineering - National Electrical Supply Co.(NESCO)
   2.  SE-1387 - Navy Department - Bureau of Engineering - National Electrical Supply Co.(NESCO)
   3.  SE-1834 - Navy Department - Bureau of Engineering - National Electrical Supply Co.(NESCO)
   4.  SE-1420 - Navy Department - Bureau of Engineering - Wireless Specialty Apparatus Co.(WSA)
   5.  IP-501-A (Commercial) S.S. Mariposa, Matson Line - Wireless Specialty Apparatus Co.(WSA)
 

Histories, Circuit Designs, Operation and Performance Testing

Restorations of SE-143, SE-1387, SE-1834, SE-1420 and IP-501-A

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

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

Navy Shipboard Radio Room  ca. 1925
SE-143 Receiver with Various "Upgrades"
The ship's Captain awaits an important message

According to RCA, the 1918 SE-143 was the first radio receiver available that performed adequately and was able to receive all types of signals whether they were from Spark Transmitters, Arc Transmitters, Alexanderson Alternators or from Vacuum Tube CW Oscillators. Surprisingly, RCA supplied manuals for the SE-143 as late as 1936. But, how could a WWI RF Tuner be in use onboard ships years after it should have been obsolete? UPGRADES! The SE-1387 and the impressive SE-1834 were especially designed, in 1922, to be used with the SE-143 (and similar Receivers) to upgrade this WWI RF Tuner into a seven-tube TRF receiver with three broadband RF amplifiers, a detector, a tunable heterodyne oscillator for CW and two stages of audio amplification. All accomplished externally with no modifications necessary other than wire-connecting these two devices to the already existing SE-143 terminals. After WWI ended, the radio receiver designs only got better with the SE-1420 Receiver that was introduced in 1919. The SE-1420 was so popular that it continued to be built as late as 1927. The SE-1420 paved the way for the incredible IP-501-A receiver that was used onboard ships and at coastal stations into the late-thirties with manuals available from RCA as late as 1938. The following examples of WWI and 1920s electro-technology illustrate how incredibly fast radio circuit designs and vacuum tube evolution were improving the communications equipment being built for commercial and military use.

Navy S.E.143 - U.S. Navy - Bureau of Steam Engineering
National Electrical Supply Company (NESCO)
SN:848N  Date on ID Plate - 1918

U.S. Navy - Bureau of Steam Engineering

S.E.143 - Short Wave Receiver - SN:848N - NESCO - 1918 Contract

The S.E.143 was a WWI Receiver that was essentially an RF Tuner (hereafter referred to as SE-143) It was used extensively by the Navy in the post-WWI era from 1918 up into the late-1920s (manuals for the SE-143 were available from RCA as late as 1936.) Other versions, like the IP-500 (usually built by Wireless Specialty Apparatus Co.,) were used on commercially-owned ships. The SE-143 was a sophisticated RF Tuner that provided a series LC Primary tuner and a parallel LC Secondary tuner. The Coupling coil between the Primary LC and the Secondary LC could be varied 90º and actually moved the coil from the control using bell-crank levers. An adjustable position Tickler coil (for VT detectors) was located inside the secondary coil form directly under a series-connected Secondary Coil extension to promote better feedback. The front panel TICKLER COUPLER control used a bell-crank lever control to rotate the Tickler coil 90º for regenerative feedback. There is also a large untuned additional Secondary coil mounted next to the main Secondary coil. The untuned secondary coil was to provide a broad response for tuning with external Crystal detectors or for finding stations transmitting on an unknown wavelength when using a VT detector. Only the Primary LC is used for tuning in "UNTUNED." When searching for unknown stations, the Coupling was set to MAX for the strongest signal albeit not a very selective response. Once the station was found, then the SE-143 could be switched back to "TUNED" allowing the receiver to be further adjusted (both the Primary and Secondary LCs) for the maximum signal level and best selectivity. Additionally, as the wavelength is decreased (higher frequencies,) the unneeded secondary coil sections are switched out (indicated on the schematic at 48-49 and 41-42.) The Primary Inductance also has switches to disconnect unneeded sections as the wavelength is changed (indicated on the schematic at 26-27 and 17-18.)

To allow the SE-143 to tune to VLF, a Secondary Loading Coil, a Primary Loading Coil and a Tickler Loading Coil could be connected using the front panel terminals so marked. The SE-143 didn't have an onboard detector or an onboard audio amplifier,...it was an RF tuner only. The VT detector was originally provided by the Audion Control Box that was designated as the SE-1071. It provided just one tube that operated as a regenerative detector for the SE-143. There was a two-stage audio amplifier available, the SE-1000 that could also be added. If the SE-143 was operated with an external regenerative detector tube, the SE-143 internally provided the "Tickler" coil (an untuned, adjustable rotational-position coil located inside the Secondary coil) connection since the regeneration function had to provide an in-phase EM field in close proximity to the secondary coil for sufficient feedback. The crystal detector function was mainly provided for emergency situations and its inclusion into the design was a stipulation of Navy regulations.

Ambiguous Tuning Range Specs Explained - The SE-143 tuning range is typically shown as 250M to 6400M (1200kc down to 47kc.) The Secondary Condenser tuning dial agrees with the 250M to 6400M range. However, the actual data plate on SN:848N indicates a tuning range of 250M to 3000M (1200kc down to 100kc.) Interestingly, the 1936 RCA SE-143 manual indicates 300M to 3200M tuning coverage (1000kc down to 95kc.) These ambiguous tuning range specifications might have been the result of the difficulty involved with adjusting the SE-143 to easily and reliably tune its full range due to the seemly insufficient Primary LC tuning range. But, with an experienced radio operator setting up the receiver, the lower end of the Primary LC tuning range can easily extend to 6400M. Usually, if the stock Primary LC versus antenna hook-up is used, the longest wavelengths can't be tuned to resonance or "peak" response using the Primary LC tuning. George Sterling's "The Radio Manual" indicates the 250M to 6400M tuning range and continues on (in the Loading Coils section) to explain how to easily change the Primary Condenser connection from the standard series LC to a parallel LC connection. The series LC presents an extremely low impedance at resonance plus a low XL (inductive reactance) that becomes "non-tunable" at very low frequencies. The parallel LC would present an infinitely high impedance at resonance allowing the LC to tune very low frequencies. Although Sterling's Radio Manual information is for extending the longer wavelength end of the tuning range to function with LF loading coils, the parallel connection of the Primary LC will allow the longer wavelengths between 3000M and 6400M to be tuned. The procedure for parallel connecting the Primary LC is simple. Just leave the PRI LOAD shunt strap in place and connect the antenna lead wire to the left terminal of the PRI LOAD. Then jumper the ANT to GR terminals with the GR terminal remaining grounded. Now the Primary LC is parallel tuned and will readily resonate at longer wavelengths.

from George Sterling's "The Radio Manual" 1st Edition - 1928

I've found that with careful set up, using the SE-143 with the SE-1387 and the SE-1834 (these units are covered in their own section further down this article) I can easily and consistently receive WWVB on 5000M or 60kc (over the air) using a 250' end-fed wire antenna. It's a very strong signal if the Primary LC is parallel tuned to resonance. Using an HP3312A signal generator set to 47kc with the output connected to a 50' wire laying on the floor and the SE-143 setup using the outdoor 250' wire antenna, I can actually receive that type of signal on the SE-143 set to 6400M or 47kc with the SE-1387 providing the heterodyne for easy detection (47kc is the absolute lowest tunable frequency possible since it's at the maximum C-setting on the Secondary Condenser dial when on Position 6, the maximum secondary L,...to tune lower in frequency requires Loading Coils.) At the other end of the range, 280M or 1060kc (AM-BC KFOY in Sparks, Nevada) is easily tuned. With careful set up on Position 1 and a series Primary LC connection, I can just begin to hear KCMY Carson City AM-BC station, a strong signal on 1300kc or about 225M (KCMY couldn't be tuned to "resonance" but the broad nature of the signal allowed detecting its lower sideband since it's a 10KW station located about 20 miles distance.) If there was a local AM-BC station on 1200kc or 250M, I'm sure it would be easily tuned in. To test 250M reception (for my location) required using the HP3312A set to 1200kc. As a "marker" signal, 1200kc was easily tuned to resonance. The confirmed actual full tuning range of SE-143 SN:848N is 47kc up to 1200kc or 6400M to 250M,...BUT, in actual tuned "over the air" signals received, the longest wavelength signal I can fully tune to resonance is WWVB 60kc or 5000 meters and the highest frequency "fully tuned" signal would be KFOY 1060kc or 280 meters. The longest wavelength limit to the tuning range is only possible IF the user is willing to switch the Primary LC from series to parallel as needed on longer wavelengths. Sterling's Radio Manual shows a DPDT switch arrangement to accomplish the series-parallel change but just moving the wires is pretty easy to do. NOTE: Using LW Loading Coils with a Regenerative Detector and 2-Stage Audio Amplifier, I can tune the SE-143 (plus LW Loading Coils) below 20kc to receive NWC 19.8kc USN MSK Sub-Comm station in Exmouth, Australia. Using SE-143 SN:848N I've been able to tune and receive stations from 1300kc down to 19.8kc, or 225M to 15,000M.

What the Specific Controls Do - The Primary Condenser dial has a 180º scale for half of the dial and linear scales for notations on the other half. The Secondary Condenser is calibrated in wavelength and also has the "letter designations" that were used during WWI and somewhat after as specifying important wavelengths (or frequencies.) Wavelength scaling is the figure shown times 100. A logging scale is also included in the other half of the dial. The inductance switches have letter designations on the Primary LC and numbers on the Secondary LC. The scales for the TICKLER COUPLER and the INDUCTIVE COUPLER are 0 to 180 with a MIN and MAX indication at each end. The scales imply the degrees of rotation for the specific coil. The BUZZER was used as a "potent" signal generator to be used when trying to find a sensitive spot on a crystal detector. The typical battery voltage for the BUZZER is no more than 2vdc if the buzzer is in good condition and adjusted correctly. There's spark gap between the ANT and GND terminals to provide a method to dissipate static charges on the antenna (common problem at sea or in windy areas.) Two sets of terminals are for LW loading coils that, when connected, allow the SE-143 to tune lower than it's 6400 meters (47kc) lower tuning limit. Additionally, a Tickler Loading Coil could be added in series with the internal Tickler Coil by using the front panel TICKLER terminals. Various types of loading coils could be used (see vintage shipboard photo further down showing a DeForest Duo-lateral LW coil apparatus being used for VLF frequencies.) The DETECTOR terminals were provided for connecting the Crystal Detector. If a Crystal Detector is used, then the STOPPING CONDENSER control can be used to select five capacitance values that are connected across the TELEPHONES terminals when DETECTOR SWITCH is set to CRYSTAL. The various capacitors were necessary to bypass any RF existing after the crystal detection. Generally, this would improve the audio response of the 'phones. The STOPPING CONDENSER isn't necessary in a VT detector and it isn't in the circuit when AUDION is selected. The eight vertically aligned terminals allow mating the SE-143 to the SE-1071 Audion Control Box. However, it's not specifically necessary to use the SE-1071. The terminals provide connections to the TICKLER COIL, AUD TEL, TELEPHONES (for Crystal Detector) and the receiver secondary LC outputs RA (grid-audion) and RE (filament-return.) The SECONDARY SWITCH allows selecting TUNED or UNTUNED with the latter routing the SECONDARY  LC to an untuned coil that's closely coupled to the secondary inductance for a broad frequency response for easier tuning when using a Crystal Detector (it can also be used with an Audion detector when searching for unknown stations.) The actual "tuning" is performed using the PRIMARY CONDENSER since the secondary is "untuned." This allows the user to tune the antenna-primary circuit to allow a stronger response for the crystal detector. Then switching to "TUNED" switches out the untuned coil and allows using the SECONDARY CONDENSER to further "peak" the signal response. As mentioned, this process can also be used with an Audion detector when searching for weak or unknown stations.

Set up for Selectable Alternate VT Detectors - The DETECTOR SWITCH routes the secondary LC as necessary for either CRYSTAL or for AUDION. It's possible to use the CRYSTAL position of the DETECTOR switch to connect to an alternate type of VT detector rather than a crystal detector. By using terminal TEL (#75) to access the RA terminal and DET (#81) terminal to access the RE terminal when the DETECTOR switch is placed in CRYSTAL, now the Secondary LC can be connected into an alternate type of VT detector. This hook-up of the CRYSTAL position was used later (in the early-1920s) when external RF amplifiers, heterodyne oscillators operating with non-regenerative detectors and audio amplifier stages became available. With this ability to have two selectable types of signal processing available using different types of VT detector circuits, the radio operator could, depending on receiving conditions, select a regenerative detector utilizing the TICKLER coil in the circuit, or he could select a circuit that provided RF amplifiers, non-regenerative detector, a heterodyne oscillator (for CW reception) and audio amplifiers. The radio operator would still have a crystal detector somewhere in the radio room and be able to connect it to the SE-143 if there was an emergency since this was part of Navy and Maritime regulations.

SE-143 Inside - RF Tuner only. Signal detection and amplification was an external function.

Refurbishment, Testing and Operation

Cabinet Work - The SE-143 cabinet is made out of walnut stained a dark reddish-brown color. The interior has no metal shielding installed. The right side front of the cabinet has two broken pieces of wood that are the full length of the height of the side piece. I had to remove the two latch-bails to be able to glue these pieces back correctly. The bottom front section is split and broken requiring gluing and clamping. I use Franklin's Genuine Hide Glue for this type of repair. This Hide Glue is not the old type (rendered from horse hoofs and hides) that needed to be a hot smelly liquid that was quickly painted on and set-up as soon as it cooled. Franklin's is synthetic hide glue with all of the good properties and minus the disadvantages. This glue is amber colored and transparent so it looks old if it happens to show in the joint. It does take a fairly long time to set-up but the glued joint has to be clamped and let set for about an hour. For full strength the glue joint must dry overnight. Unfortunately, with these types of breaks, I have to use a combination of hand clamps and pipe clamps because of the distance between the glue joint and the back of the cabinet and because of the angle of the breaks. The need for pipe clamps is common with most cabinet repairs involving glued joints. The complete gluing took about a day to accomplish and used three pipe clamps and about half a dozen hand clamps.

I do have the rare front cover for this SE-143. It has had some crude repairs done to it. The cover piece of wood was replaced with 1/2" plywood, apparently many years ago. It's stained to a color that's sort of close and has a vintage-look to it. Also, one of the side pieces was replaced and the dove-tail joints not reproduced. Instead, the "dove-tails" were cut off and the wood nailed in place. It's pretty crude. Overall, the condition is probably a little worse than average BUT, at least, I do have the top cover, which is rare to find with an SE-143 receiver. 

The back of the cabinet ended up missing sometime in the past. Someone cut some 1/4" birch plywood, glued two pieces in a sandwich to create a 1/2" thick, stepped-type of back that fits okay. It wasn't stained and finished however, just left bare wood. Luckily, it's mounted with only four screws, so it can be easily removed for rework and staining. I have lots of red mahogany stain but I think I'll have to mix some golden oak in to get the correct color. I'll also work on getting a better fit, touching up the edges so they don't look like plywood and then stain to match. For the time period and that fact that most of the SE-143 receivers were expected to be "at sea" I'd expect varnish was the original finish used. However, after 100 years, there's not too much original finish left now.  NOTE: Close examination of the SE-143 cabinet with this make-shift cover removed seems to indicate that perhaps there never was a rear cover. I can't find any residue of glue, there are no nail or screw holes. I can't imagine that there wasn't a back to the cabinet,...I just can't find any evidence that shows how one would have been installed. However, since this make-shift cover fits and after staining it matches fairly well, I'm going to install it. If I find out later that SE-143 cabinets didn't have back covers, it can easily be removed, though a side-benefit of this back cover is that it significantly strengthens the cabinet joints.

Crystal Detector Test - The next test was to connect a crystal diode (1N34 germanium diode) to the CRYSTAL terminals (it doesn't matter for the cathode or anode connections.) I connected a set of Baldwin Type-C 'phones to the TELEPHONE terminals. I placed the DETECTOR SWITCH in the CRYSTAL position. I had the SE-143 tuned to 1000 meters or 300kc and the HP-606 was also tuned to 300kc modulated at 400hz. The signal came over the 'phones quite well. It did require a little bit of peaking of both the Primary and Secondary tuners for a maximum response. I tried a few other frequencies and was able to tune them in quite well.

Signals "Over the Air" Test - Next was to try an actual "over the air" signal. About the strongest MW signal around here is from KKOH on 780kc or about 385 meters. I used the HP-606 to pre-tune the SE-143 for 780kc. I connected one leg of the Collinear Array for the antenna (about 250 ft end-fed wire) and used the house ground. KKOH 780kc was easily audible and, with a little peaking, it was coming in strong using the 1N34 crystal detector. I tuned in a couple more BC stations, KPLY on 630kc and KOLO on 920kc. With the COUPLING on 110, I had enough selectivity to separate these stations easily and still maintain a good signal level. I tuned to "S" which is the WWI letter designation for 100kc (3000 meters.) This is the transmitting frequency of the LORAN-E Master Station "M" located in Fallon, Nevada about 50 miles east of my QTH. "M" runs 400KW to a 625' tall ground isolated vertical with a 900' C-hat,...it's a formidable LF signal here in Dayton Valley. "M" was easily tuned in and peaked with the Secondary Condenser exactly on "S." If the TICKLER coil is shorted for CRYSTAL detector operation (as when using the SE-1071) then the TICKLER COUPLER should be set to MIN to minimize coupling losses in the Secondary Inductance.

"IN and OUT" test, showing the output at RA/RE (Secondary LC) - 500kc sine wave input on ANT input from HP-606B with no modulation. The FNIRSI DPOS350P shows 500.3khz on the DFC and shows the output is 1.82VP/P. This preliminary, no detector, test showed that a signal could make it from the Antenna to the "Tuned Output."

The Hook-up - To operate the SE-143 with a VT requires a vintage triode tube and tube socket, an adjustable filament voltage source and another adjustable voltage source to provide plate voltage. A couple of things to observe are RE is connected directly to F- and B- is connected to F+. The 'phones are connected to the AUD TEL terminals. The plate voltage B+ is also connected the lower AUD TEL terminals that has one lead of the 'phones. The top AUD TEL terminal has the other lead of the 'phones but also has a jumper to connect the upper AUD TEL terminal to the lower TICKLER terminal (the use of the AUD TEL terminals was later found to be unnecessary.) Then the upper TICKLER terminal is connected to the Plate terminal on the tube socket. The jumper has to be externally installed because this connection was actually made inside the SE-1071. Additionally, the connections to 'phones, Tickler Coil and VT plate were all internal to the SE-1071 and controlled by a switch that selected OSCILLATOR (Regen going through the Tickler coil) or DETECTOR (Tickler coil shorted for a non-regenerative detector.)

The Ship's Generator as a B+ Source - Interestingly, the SE-1071 could provide B+ plate voltage either from storage batteries or it could be provided by the ship's +125vdc generator. There was an adjustable potentiometer to adjust the plate voltage but the +125vdc ship's generator only has a couple of filter chokes inline inside the SE-1071, so one has to wonder exactly what the plate voltage was and what the value of the variable resistance was (neither are indicated anywhere on the SE-1071 schematic. Sterling's Radio Manual indicates the resistance was 30,000 ohms. Plate voltage could be adjusted between +60vdc and +90vdc if the ship's generator was used.) There's a switch and terminals provided for selecting either storage batteries or the ship's generator as a B+ voltage source. If the SE-1000 Audio Amplifier was also to be used, then the ship's generator couldn't be used and only storage (or dry) plate batteries could be used. When using B batteries, the adjustable plate voltage function is disconnected.

Vacuum Tubes Available in 1918 - Another consideration is the actual type of vacuum tube used in the SE-1071. In 1918, a Moorhead "ER" Electron Relay tube might have been used or perhaps a Western Electric VT-1. Other tubes specified in Sterling's Radio Manual are the Western Electric W-933 or the General Electric CG-890. Both of these tubes have 1 amp filament requirements indicating a pure tungsten filament and a plate voltage specified from +20 up to +60vdc. The specs of those two types of VTs are similar to the UV-200 or UV-201 but those tubes weren't introduced until around late-1921, along with most of the other consumer-broadcast radio vacuum tubes (although the UV-200 or UV-201 tubes weren't available in 1918, they can, of course, be used today.) Apparently, in late-1920 and through most of 1921, Westinghouse supplied WR-21 tubes that were similar in specifications to the UV-201 (4vdc@.8A compared to 5vdc@1A) however the socket required for the WR-21 was different. The WE-215A tube might have been available in 1919, but the special socket required for that tube seems to eliminate it for use in the SE-1071. The most likely VT used in 1918 would have been the WE VT-1 or the Electron Relay (there were several manufacturers for the ER type of VT during WWI) or those specified in Sterling's Radio Manual. For initial testing of VT detector and regeneration, I'm going to use the UV-200.

What Doesn't Work - My first attempt with the UV-200 had clip-leads improvised with very long lead connections and didn't follow what the SE-1071 schematic indicated. As expected, while this lash-up worked fine as a non-regenerative Detector, I couldn't get the Detector to break into oscillation. I tried using a UX-201A and a Type-30 with the same results. I tried plate voltages from a low +15vdc up to +70vdc and could never get any of the Detector tubes to oscillate.

What Does Work - Finally, I decided to follow the SE-1071 schematic and hook-up closely, in fact, almost exactly. I used wire connections that were as short and direct as possible. I connected one lead of the 'phones to the lower TICKLER terminal and the other 'phones lead to +45vdc. The upper TICKLER terminal was connected to the detector tube plate. Connecting to the AUD TEL terminals isn't necessary. I think the non-oscillating problem was that initially I had connected the RE terminal to F+/B- but, the SE-1071 schematic shows RE connected directly to F- battery terminal. I made the change so that the F- connection agreed with the SE-1071 schematic. I replaced the 250pf grid blocking cap with a 500pf. The grid blocking cap is a switch-selected value in the SE-1071 and 500pf is in the middle of the range of capacitors. I changed the grid-leak resistor from 1.2meg ohm to 680K (600K on the SE-1071 schematic.) I connected the grid-leak to B- as indicated on the SE-1071 schematic rather than in parallel with the grid blocking cap. I installed a 0.004uf capacitor from the junction of the 'phones and the Tickler coil as indicated on the SE-1071 schematic. It's a switch-selected value but the capacitor values aren't shown on the SE-1071 schematic. The capacitor shunts any RF on the 'phones to B-.  NOTE: Experimentation has shown that this capacitor is essential for allowing the detector to oscillate. Also, something to consider if AF amplifier stages are added and this capacitor is moved to the primary of the first interstage transformer. If the capacitor is connected to B-, then, if the capacitor shorted, the increased current flow through the transformer primary could cause it to "go open circuit." Most circuits will have this capacitor connected to Detector B+ (across the primary using Det B+ as a low impedance source) where it still functions as needed and if the capacitor shorted it wouldn't damage the interstage transformer.

Following the SE-1071 schematic and the hook-up exactly as shown resulted in tremendous regeneration capabilities with being able to easily adjust the TICKLER COUPLER for detector oscillations.

In actually operating the SE-143 and testing various wavelengths of reception, I've discovered that it helps to have the filament voltage adjustable. The B+ can be a fixed value. I used +45vdc on the detector plate. I found best improvement was when I eliminated as many of the clip-leads as possible and installed wires that were soldered to lugs that were then installed to the tube socket terminals. Where the wire went through the hole in the SE-143 terminals I tinned wire end to make as good of a joint as can be expected from thumb-nut terminals. Also, making sure that the RE terminal connected directly to F- and that the filament adjustment pot was connected from F- on one end and to F- at the tube socket on the other end. With careful wire connections that followed the SE-1071 schematic, I was able to tune down to 5000M (60kc) and could easily maintain an oscillating condition for the regeneration. 

Adding a Single Stage of Audio Amplification - I have a Pilot Radio Redi-Blox Single Stage Audio Amplifier from about 1930 that I use with the SE-1420 receiver to boost the output of the detector tube for that receiver. It provides enough audio level to actually hear very weak signals, like NDBs, using headphones. I've also used this audio amplifier with the Spherical Audion Receiver with good results.

To hook-up the single-stage AF amp, the primary winding of the input transformer is connected to the two points where the headphones were connected,...to the lower TICKLER terminal directly with one end of the primary and the other TICKLER terminal connecting to the detector plate. The other transformer primary terminal is connected to detector B+ with the voltage being +45vdc for a UX-201A tube. For the Audio Amplifier tube I use a UX-201A tube and use +90vdc on the plate and that is routed through the 'phones before going directly to the amp's plate terminal. The F+ and the B- are connected to the B- terminal of the A-B power supply (B- is connected to F+.) Audio Output can be controlled by the tube filament voltage. A 1920s Horn Speaker could be used on just about any of the AM-BC stations. Hearing NDBs (the few left, anyway) will require 'phones and listening during LW Season (between the Autumnal Equinox and the Vernal Equinox - definitely not in mid-July.) The NDBs are MCW signals but having the detector oscillating will make finding the NDB's carrier easy. Just tune for zero-beat and the MCW tone will be easy to copy. 

The photo to the right shows the SE-143 after cleaning and installation into the repaired cabinet. The white and black leads near the Buzzer are the Antenna and Ground connections. The antenna is one half of a Collinear Array or about 250 feet of wire that's end-fed and the ground is a combination of the house ground and a large counterpoise. The power supply is a homebrew, active regulated type with full switched metering. I designed and built this A-B-C eliminator in the late-1970s when I had practically unlimited new parts available at no cost. Filament supplies are +1.5vdc, +4.5vdc and +6vdc and use 3A active regulators. B supplies +22.5vdc, +45vdc, +67.5vdc and +90vdc are actually four completely individual +22.5vdc power supplies with their own power transformers with 1A active regulators. The B supplies are connected in series for the B voltages. The C bias supply is -4.5vdc uses a small active regulator for 200mA. I also built-in switched metering for A and B supplies. The A meter switch also selects which filament voltage appears on the A terminals. I should have made the A supplies adjustable but since they aren't, I've connected an external filament rheostat (0 to 10 ohms adjustable.) I've eliminated as many of the clip-leads as possible. Most wires are soldered to lugs that are then installed to the terminals. This careful setup has resulted in a greatly improved performance.

SE-143 with VT Regenerative Detector and Single Audio Amplifier is tuned to 5000M or 60kc receiving WWVB PE Time Signal. As to the "haphazard" interconnect wiring,...the SE-143 manual does state that the wires shouldn't be "bunched" - they aren't.

Since the SE-143 has absolutely no shielding, when the regenerative detector is oscillating there will be some "hand-capacitance effect" on the TICKLER COUPLER control, on the SECONDARY INDUCTANCE SWITCH and to a lesser extent on the SECONDARY CONDENSER and the INDUCTANCE COUPLER controls. Since these components are part of the oscillating detector there's an associated EM field around the components and when the hand is on the control knob there will be a slight de-tuning because the hand adds "capacitance to ground." This is a common effect with unshielded regenerative receivers. The hand-capacity effect lessens as the wavelength lengthens, that is, the lower the frequency the less hand-capacity effect will be experienced. The SE-1420 solved this problem by entirely shielding the front panel and the cabinet along with a divider shield between the Antenna Tuner and the Secondary LC.

Summer conditions are terrible for MW and LF reception,...but I thought I'd try to at least receive the NBD MOG 405kc located in Montegue, California. It's the closest NDB to Dayton Valley, Nevada that's still in operation with a distance of about 150 miles. I pre-tuned the SE-143 using a signal generator for the marker signal. With a slight amount of "peaking" I was able to hear MOG very well. Time of reception was 2135hrs PDT on Jul 14, 2026. I tuned around by didn't hear any other NDBs (and that's not particularly surprising for mid-July listening.)

Since a clip-lead connected regenerative detector and single stage audio amplifier using components that are just setting on the table tend to be unstable, I thought I'd go ahead and build something a little better,...

Building a Regenerative Detector, 2-Stage Audio Amplifier for the SE-143

Schematic for Regenerative Detector and 2-Stage Audio Amplifier

Using Just the 2-Stage Amplifier for the SE-1420 - It's very easy to bypass the D-A detector stage and access the first interstage transformer primary to provide a 2-stage AF Amp for a single-tube regenerative detector receiver, like the SE-1420. The D-A interstage primary substitutes for the TELEPHONES input but the SE-1420 supplies the Det plate voltage. Just connect the lower TICKLER binding post on the D-A to one of the SE-1420 TELEPHONES terminals and the D-A DET B+ binding post to the other SE-1420 TELEPHONES terminal. Turn the D-A Det Fil rheostat to OFF. DO NOT connect the D-A DET B+ to an external voltage, the SE-1420 will supply the detector plate voltage. D-A filament voltage is required for the Audio tubes only and is controlled by the Amp Fil Rheostat, the +90vdc Audio tubes plate voltage and the -4.5vdc C bias voltages will still be required as will the filament and detector voltages for the SE-1420.

Using the Homebrew D-A with the SE-143 - I used the homebrew A-B-C supply with +45 Det B+ and +90vdc Amp B+. The -C bias was -4.5vdc and the A supply was +6.0vdc. The capacitor across the first interstage primary is essential in order to shunt the RF to a low Z (low-impedance in this case is B+ and don't connect the capacitor to A+B- because if it shorts-out the excessive current flow could cause the primary winding of the transformer to go open-circuit.) Without this capacitor installed the SE-143 won't regenerate. Also, +45vdc is necessary on the Detector plate for regeneration below 100kc (+22.5vdc isn't enough plate potential for regenerative oscillation at the lowest RF frequencies.) All of the controls that are adjustable will have an effect on reception, so expect a lot of interaction. The easiest method is to set the COUPLING to the desired selectivity, around 60 is okay to start. Then tune the Secondary LC to the approximate wavelength and adjust the TICKLER for oscillation. Then peak the Primary LC. It requires going back and forth a lot to get all of the adjustments correct for maximum signal response,...and that's normal for a regenerative detector tuner. Setting "Critical Coupling" is very important with three-circuit tuners with regenerative detectors. To set "Critical Coupling" requires the following steps,...after the station is tuned in, then use the Primary Condenser to "tune through" the signal. If you hear the regeneration "click" or "shut off," then the Coupling is too tight and needs to be loosened, that is, reduced. Turn the Coupling control to a lower number on the scale, e.g., if you were at 60, lower it to 40, then tune through the signal with the Primary Condenser again. If the signal still "clicks" or "shuts-off," reduce the Coupling to an even lower number. Repeat these steps until as you tune through the signal with the Primary Condenser it just peaks with no "clicks" and no "shutting off." Now the Secondary Condenser can be used to peak the signal and the Tickler adjusted for maximum sensitivity. Setting "Critical Coupling" is very important when searching for weak CW or MCW signals and requires that both the Primary and Secondary condensers are tuned together for maintaining peak signal response. I was able to easily achieve feedback down to 50kc (with +45vdc Detector plate voltage.) I did most of the listening on LF with WWVB 60kc, the USN MSK station on 72kc, Loran-C 100kc used for testing. AM-BC was also used for testing. All signals were monitored on a Western Electric 10-D horn speaker. Aug 19, 2026 - Using LW Loading coils and the D-A, I was able to receive NWC 19.8kc USN MSK Sub-Comm Station in Exmouth, Australia. Also, NPM 21.4kc in Lualualai, Hawaii and NAA 24.0kc in Cutler, Maine and NLK 24.8kc in Jim Creek, Washington,...all listening over the WE 10-D Horn.

Det-2AF Amps with used parts and Breadboard construction. The tubes are 201-A types, the matching interstage transformers aren't marked so the maker is unknown. Most of the wire used was vintage solid conductor that allowed for nice bending for the routing of the wires. The blue tape markers identified the proper connections for the interstage transformers.

I've searched and searched the Internet (and AI) and I've never found anything on these "letter to wavelength" assignments although they were obviously in use during and after WWI by the U.S. Navy and probably the U.S. Army Signal Corps and the U.S. Coast Guard. I've always been curious why the letters were present on these dials. They must have been to ease the tuning difficulties when trying to set up the receiver to specific wavelengths (all those numbers that required multiplying by 100 for the actual wavelength must have been confusing to neophyte radio operators.) The combination of a specific letter plus (maybe) the numerical indication on the 0-180 scale would have been an accurate "set up" method that probably referenced some sort of chart that gave all of the proper control settings for the receiver to operate correctly on a desired wavelength using a specified antenna. I've never seen a copy of this type of chart, or even heard of one,...a "letter wavelength reference chart" isn't mentioned in any of the wireless books that I've seen. Nothing is mentioned in Sterling's Radio Manual. Another hint at their use is that the letters are on the Secondary Condenser Tuning dials of the SE-143 and SE-1420 BUT the letters aren't on the Secondary Condenser tuning dial of the IP-501-A, a commercial receiver. That would seem to date the use of the letters from WWI to maybe a short while after that, about 1920 or so. By 1922, the letters weren't needed and weren't included on the Secondary Condenser tuning dials. I decided to do a test to find out what wavelengths the letters indicated. I don't think any definite answers will be forthcoming but it would be interesting to see what wavelengths were involved.

NOTE 1: Where did this SE-143 come from? I received a 'phone call from Ethan, the owner of Ham & Hi-Fi in Sparks, Nevada, saying "I have something here that's right up your alley!" He was right, of course. I had to think about it for a couple of weeks due to the condition problems. Ethan had texted me a few photos of the receiver that showed some of the issues (that looked worse than they actually were.) When I decided to go ahead with the purchase, then Ethan was out of town for about three weeks. Finally, after our mutual delays, I was able to purchase the SE-143 on June 30, 2026. Ethan told me that the SE-143 had been stored in Santa Rosa, California.

NOTE 2: The U.S. Navy created the Bureau of Steam Engineering in the 1860s as a technical engineering department, initially to help with the transition from sailing ships to steam powered ships. Later, new technologies like electrical and wireless engineering were added. In 1920, the name was changed to Bureau of Engineering and, in 1940, it was renamed Bureau of Ships.

NOTE 3: Although I've seen some written references to an "A" version of the SE-143 (supposedly designating the NESCO builds,) I really haven't found any early (contemporary to the SE-143 production and use) that specified that an "A" version existed or, if it did, what an "A" version consisted of. That being said, there are many variations of the SE-143. There's a photo of one on the Internet that has a reddish-brown panel, cabinets can be found in walnut or oak, there are variations in the buzzer buttons, at some point the CRYSTAL-AUDION switch nomenclature was changed to AUDION-SEND-CRYSTAL with the AUDION and CRYSTAL positions exchanged and a SEND position added (probably the mid-position where the knife-switch arms don't contact either of the stationary receptacles.) Some variations were probably due to specific builders and might also be differences between the SE-143 and the IP-500. 

NOTE 4: The "Short Wave" designation is relative to the time period and to the typical frequencies that the Navy used during WWI. A more modern designation would be that the SE-143 is an LF/MW RF Tuner-Receiver (Low Frequency or LF is from 30kc to 300kc and Medium Wave or MW is from 300kc to 3000kc.)

SE-1387 - R.F. Driver (Tuned Heterodyne Oscillator)  SN: 15N
  SE-1834 - Amplifier, Radio-Audio 125-30,000 Meters, Audio Universal
(3-stage Broadband RF amplifier, Detector, 2-stage AF amplifier)  SN: 14N

Navy Department - Bureau of Engineering - National Electrical Supply Company (NESCO) - 1922 Contract
 

Post-WWI Radio Improvements - As radio evolved post-WWI, the need for new radio equipment was offset by the reduced post-war Navy budget that limited extravagant purchases to a certain extent. This resulted in the newest and largest Navy ships being prioritized for the newest equipment while an older or smaller ship would have to utilize older, maybe even WWI-era, radio gear. Improvements were much easier to fit into the budget and, as radio evolved, these external circuit additions allowed older radio equipment to be updated to provide usable service. Most peripheral equipment came in the form of RF amplifiers to be used ahead of a regenerative detector provided stronger signals and antenna isolation. Audio amplifiers to provide stronger post-detection signals to drive multiple outputs. Devices for interfacing specialized antennas such as loop antennas for direction finding. By 1922, there were several types of "add-on" devices available to improve the performance and usability of older receivers. This SE-1387/SE-1834 combination (shown to the right) was specifically for the SE-143, IP-500, SE-1220 or other similar RF Tuners.

Although the SE-1387/SE-1834 combination appears to be a receiver, it's far from being a "complete" receiver. The SE-1387 is actually a "tuned" Heterodyne Oscillator and the SE-1834 is almost a complete receiver but it's minus any selective RF tuning capability. Both units have to be used with RF Tuner sets like the SE-143. Unlike the earlier shipboard radio equipment that were housed in wooden cases, perhaps lined with metal shielding, the SE-1387/SE-1834 combo was built with aluminum front panels and housed in an aluminum case. Both units are installed into individually shielded compartments to prevent any stray coupling between the units. The size of the metal cabinet matches the height of the SE-1420 so it's somewhat smaller than the enormous cabinet of the SE-143. Most Navy installations would place the "add-on" units on top of the SE-143 and wires interconnecting the units were routed around the panels to access the needed terminals. Although this particular example has the SE-1387 and the SE-1834 housed into a single cabinet, most vintage photographs show individual "add-on" units were single-function devices that were housed in their own individual cabinets (see the vintage photos further below.)

SE-1387 & SE-1834
Combination RF Driver and RF-AF Amplifier & Detector

RF Driver (Heterodyne Oscillator) SE-1387 - The Oscillator tuning condenser is controlled with a two-speed tuning dial assembly.

SE-1387 - better view of Oscillator coils and the moveable shielded Coupling coil.

Shown in the photo to the right is the "Eaton Circuit Driver" built by Wireless Specialty Apparatus Company. The Eaton Circuit Driver was an Eaton Oscillator to which was added a tube socket, an amp meter, a buzzer and a filament adjustment pot. Like the standard Eaton Oscillator, the Eaton Circuit Driver was connected into the secondary LC of a tuner to provide a constant oscillation that didn't depend on the tuned frequency. The "Undamped" selection would have this device perform as the normal Eaton Oscillator. The "Damped" selection added the buzzer to the circuit, apparently "driven" from the received signal to produce a buzzer-modulated signal for wavemeter calibration purposes. The vacuum tube pictured is probably an Atlantic-Pacific ER or a Moorhead ER. This photo is from "Design Data for Receivers and Transmitters" by Milton B. Sleeper, 1922.

Universal RF-AF Amplifier-Detector SE-1834 - The front three units are four-band RF amplifier coils. Note the wooden framework on RF1 and RF2 coils. The rear two units are Audio interstage xmfrs. The front three tubes are RF amplifiers, then the detector and the rear two tubes are the Audio amplifiers. The RF range switch selects one of four different, broadly tuned RF inductances in each RF transformer (selecting both the primary grid winding and the secondary plate winding.)

SE-1834 - Note the RF range switch. The meter is 2vdc FS and optimized for the 1.0vdc filaments of the WE 215-A tubes.

Where the SE-1387/SE-1834 Came From - Fellow LW enthusiast, Dave Samson, gave me this SE-1387/SE-1834 Combo about six years ago, in August 2020. Dave shipped it from his QTH in Western New York out to Nevada along with a FTC/Mackay RC-123. When I inspected the unit, the first thing I noticed was that it used WE 215-A tubes and all seven tubes were gone. I didn't have any WE 215-A tubes left. I had sold most of my collector tubes,...to a tube collector,...and the WE215-A tubes (five of them) were part of the sale. I did a visual inspection through the two top lids but never took the two units out of the cabinet. That resulted in an assumption that the SE-1387 and SE-1834 were some type of RF amplifier. Not quite six years went by and I then acquired the SE-143 receiver. In some way, I knew that the SE-1387 and SE-1834 required an RF Tuner like the SE-143. That piqued my interest enough to disassemble the unit and see exactly what it was supposed to do.

The Interconnection and Operation - The SE-143 RF Tuner was directly connected to the SE-1834's three stage, RF transformer-coupled RF amplifier by connecting the SE-143 RA and RE terminals to the RECEIVER terminals on the SE-1387. It was mentioned in the SE-143 manual that since the RA wire is a "grid connection" it had to be isolated, as much as possible, from other wires ("not bunched with the other wires" was the terminology used.) However, note that the SE-1387 terminals do provide a grounded SHIELD terminal implying that the RA/RE SE-143 connection should use a shielded cable. Internally, the RECEIVER terminals connect directly to the AMPLIFIER-GRID terminals and are "strapped" to the GRID INPUT of the SE-1834. This allowed the SE-143 a direct connection via its RA terminal to the first RF amplifier grid. The SE-143 Secondary LC ground-return is routed through the pick-up coil in the SE-1387 to allow the heterodyne oscillator to modulate the incoming signal to the SE-1834 RF amplifier grid (if the SE-1387 is powered-up.) Since the heterodyne is modulating the ground-return, there is a wire-wound resistance that's adjustable to "stabilize" the actual heterodyne versus signal ratio. The actual practicality of this connection relies on the oscillator coupling coil having a low enough impedance and that the oscillator has enough pk-pk voltage output to overcome the losses of this type of hook-up. As mentioned, this hook-up is implied by the location of the terminals and, without any documentation, an actual functioning interconnection has to be determined by experimentation using operational equipment. Testing and actual operation has shown that this hook-up works quite well.

The RF amplifiers were broadly tuned via three RF transformers that provided four broadly-tuned ranges. This is essentially also where the incoming tuned radio signal was heterodyned with the SE-1387's variable-coupled oscillator output to allow detecting CW signals from VT, Arc or Alternator transmitters. The output of the 3rd RF amplifier stage was then routed to the detector stage. The output of the detector was routed to a two-stage, transformer-coupled audio amplifier. The audio output was routed to the TEL. terminals. Total gain was controlled by the filament voltage control and by the STABILIZER control. The purpose of the switch RADIO-AUDIO/AUDIO is to allow all filaments to operate in the RADIO/AUDIO position and turns off the filaments to the Detector tube and the two AF amplifier tubes in the AUDIO position allowing just the three RF amplifier tubes to operate (although this seems opposite of the expected function, measuring the continuity confirmed that the detector and audio tube filaments are turned off in the AUDIO position. However, the nomenclature might imply using only the SE-1837 RF amplifiers ahead of the receiver's regenerative detector and audio stages. There's also the possibility of a 1920s vintage modification since it appears that a few wires that should be present, aren't.) The STABILIZER control is a wire wound resistance of the SE-143 RE connection terminal (secondary tuned LC ground return) to the B- line. The FILAMEOSTAT adjusts the filament voltage on the WECO 215-A tubes (set to less than 1vdc fil voltage.) For use of the SE-1387/SE1834 combo, the TICKLER terminals have the strap installed and the AMPLIFIER-GRID INPUT straps are also installed. If just the SE-1834 was used with an SE-143 RF Tuner, it would be possible to remove the TICKLER strap and use the TICKLER connections on the receiver for a regenerative detector. The RA-RE connections on the SE-143 would then be connected to the SE-1834 GRID INPUT directly. Again, these are implied connections. An actual functioning hook-up has to be determined by experimenting with operational equipment. I have operated the SE-143 with the SE-1834 set up as a regenerative detector utilizing the SE-143 Tickler and it functions very well.

There was an SE-1834A version that eliminated the filament voltage meter (shown in two of the vintage B&W photos further below.)

The Western Electric Co. 215-A tube - WECO 215-A tubes, also known as VT-5 or D-80039, are very similar internally to the WD-11 tube. However it's quite probable that the internal design of the later WD-11 that was used in Westinghouse-RCA battery operated Broadcast consumer radios from 1922 up to 1925 was actually based on the 215-A since Westinghouse and AT&T (Western Electric) were cross-licensed in the GE-RCA "Radio Group." The 215-A tube envelope and base are significantly smaller than the WD-11. The tube socket is unique and only fits the 215-A. Filament specs are 1.0vdc at .25A (WD-11 is 1.1vdc at .25A.) If the filament structure is like the WD-11/WD-12, then the 215-A uses an iridium-platinum ribbon that's oxide-coated. The 215-A behaves like a WD-11 in that filament emission takes place at a very low temperature and low current level (much lower than the 1vdc at .25A spec.) Most of the time, the 215-A filament isn't really incandescent at all but the emission is at specifications. In a day when a typical UV-201 tube required 5vdc at 1amp and the pure tungsten filament incandesced like a 5 watt lamp, the 215-A and the WD-11 behaved quite differently with many users unnecessarily increasing the filament current up to the point of filament incandescent visibility with disastrous results (depleting the emitting component of the oxide coating due to excessive heat.) Plate voltage maximum is +100vdc though usually the tubes are operated at +40vdc to +60vdc. The amplification factor is typically about 5 but could go up to 7 or 8 at higher plate voltages and if the tube has good emission. The 215-A tube was only used for a short time and was commonly found in the Western Electric Broadcast Monitoring Superheterodyne Receivers, like the 3-series and 4-series, also other WE BC monitors and apparently in a hearing testing device. Its common use was in the period of 1921 up to about 1928 although there are some indications that the U.S. Navy had some use for 215-A tubes as late as the early-1940s (a 1944 contract.) Although the WD-11, WD-12, WE239A and, the more modern replacement, the RCA 864 all have almost identical specs as far as the tube elements and function, the physical structure of these electrically-similar tubes is completely different. For initial testing, since I sold my collector tubes years ago that had included five good 215-A tubes, I'm going to have to buy seven of them,...ouch! The WE215-A is relatively inexpensive but the WE239-A is astronomically priced (WE tube dealers,...and for an anemic triode with an amplification factor of 5???) WD-11/WD-12 tubes seem to be somewhat fragile because most of the ones I've found had open filaments. I'm going to use the 864 tube for initial testing. It's a little more stoutly built and seems to function okay as a substitute. It's a moderately priced tube but I have several of them that didn't get included in the collector tube sale. I only used the 864 until I actually had a WE 215-A tube to use.

IMPORTANT NOTE on Feb 1944 Contract "NAVY" 215-A tubes: 215-A tubes that are from a USN contract from February 1944, Contract No. N140S21722A, will have "NAVY" stamped in orange paint on the base of the tube. This particular contract was built by Western Electric but the bakelite bases used in this manufacturing run are slightly larger than earlier manufactured tubes. It appears from actually measuring the bases that these 1944 WE versions have bases that are between .005" up to .010" larger in diameter than earlier tubes. These 1944 tubes are a "tight fit" but I've had two of these particular type of 215-A tube that became stuck in the tube socket and couldn't be removed. I couldn't turn the tube so it wouldn't "lock in" and, being wedged in place, I couldn't remove the tube either. Disassembly of the socket was necessary to remove these particular contract 215-A tubes (needless to say, the removal process ruined the tubes.) Perhaps other runs of 215-A sockets other than what I have here (the SE-1387 and SE-1834) might not have this problem. All earlier built WE215-A tubes fit into the sockets easily, just the tubes with the orange "NAVY" on the base have problems with the base fitting into the socket. There's really no good solution to this problem. It would be possible to enlarge the tube socket base hole itself but modifying an original socket just for one contract type of 215A tube isn't a desirable option. Trying to work with the tube base itself would probably end up ruining the tube. Pre-testing the 215-A "NAVY" tube (1944 contract) would be the good solution but probably not practical since purchasing these tubes is almost always an online buy from eBay dealers (I doubt any of the eBay tube dealers would be willing to use dial calipers to actually measure the base diameter - but that would be a practical solution.) I had three of these original boxed 1944 NAVY 215-A tubes,...one fit snuggly but was okay to use. The other two ended up being destroyed because they became "stuck" in the socket.
 

SE-1387 - Circuit Analysis, Testing, Restoration There are no schematics available for the SE-1387 or the SE-1834. In fact, there's no documentation available, at all. I've had to trace the wiring to see what the circuits were intended to do when interconnected to an RF tuner like the SE-143. The circuit is a grid-leak oscillator with tightly coupled grid and plate coils. The grid coils connect to the variable condenser to allow the LC to function as a frequency adjustment. The range switch is double-function and selects both the correct grid coils and the correct plate coils simultaneously for a specific tuning range. The oscillator output is coupled by an adjustable "pick-up" coil (COUPLING) that is shielded with non-ferrous metal to allow magnetic pick-up only. The "pick up" coil connects in series between the SE-143 secondary LC ground return (lower Receiver terminal) and the lower Amplifier terminal. My analysis that the tuned oscillator is to provide an on-frequency heterodyne for CW reception is based on the increasing use of CW in place of Spark transmissions at the time and how later "Tracking BFO" TRF receivers were designed. Vintage photos helped to actually see how these devices were connected to the SE-143 in particular. However, the final analysis will be to confirm the SE-1387 does function as I think it should. This will require a functional WE 215-A tube. That should provide functionality for the SE-1387 and, with an oscilloscope and a LF-MW receiver, I would be able to see and hear the oscillator output. I've tested all of the coils in the SE-1387 and they all show continuity, so the testing will begin as soon as a good WE215-A is purchased and delivered. I did find a broken solder joint that was on the B+ buss to the plate coils (standard soldering technique of the 1920s using buss wire and "tack soldering" is very prone to breakage,...especially after 100 years on the Planet.) Testing has shown that the implied Filament voltage at the supply was 2.5vdc however, 2vdc is shown on the front panel.  This level allows the INCREASE pot to provide +1.0vdc to a .25A load at the tube filaments with the adjustment at about mid-scale (although the 215-A tube has sufficient emission well-below the +1.0vdc specification.) Also, A+ is connected to B- and both terminals are connected to the shield-chassis front panel ground. For initial testing (before I actually had a 215-A tube,) I used an RCA 864 tube that I connected into the circuit with clip-test leads. Amazingly, this did function exactly as expected but the final testing will have to wait for the 215-A tube to arrive.

The test set-up showing SE-1387 producing a 500kc (600 meters) waveform

The Test Set Up - I used an adjustable Lambda power supply with a voltage range of 0 up to +30vdc at 2.5A. I set the output voltage to +2.5vdc with the wires connecting to - and + FIL BAT terminals. The B+ power supply is an RCA dual bench supply with a range of 0 to +20vdc from each supply. I connected the two supplies in series to have +40vdc B+ with the wires connected to PLATE BAT + and - terminals. The SE-1387 monitoring was provided by the FNIRSI DPOS350P. This is a small, tablet-size, modern piece of multi-function test equipment that runs on a rechargeable battery. I'm using the oscilloscope to monitor waveforms. Also provided by the DPOS350P is the waveform frequency and the P-P voltage and a lot of other parameters of the waveform. Accuracy of the SE-1387 dial is good with 500kc showing slightly off from 600M. The 2.008mHz waveform showed 150M on the SE-1387 dial,...not bad for an oscillator that's over 100 years old.

Looking over the top of the SE-1387 showing the WE215-A tube installed, the 150K grid resistor, the non-ferrous metal shielded pickup coil and the grid-plate coils

Waveform on Range A at 150 meters or 2.008mHz VP/P=230mv

215-A in SE-1387 - UPDATE: I've run into this problem many times, especially on 1920s tubes. When the 215-A tube arrived, it looked NOS in the original box, but testing the filament continuity showed it was open. Visual examination with magnification revealed that the filament was intact. I re-flowed the solder on the base pins and checked again. This time I had continuity. I did the same re-flowing technique on the grid and plate pins. When the 215-A was installed, at first it didn't oscillate. I increased the filament supply up to +2.5vdc with the INCREASE control about mid-point for just about +1vdc on the filament. The 215-A started to oscillate. I checked ranges A and B with no problems in operation. Subsequent testing confirmed operation on all five ranges. The filament of the 215-A is oxide-coated so as the tube is used it should continue to improve emission. Only use just enough voltage for circuit operation. Excessive filament brilliance will quickly deplete the tube of its ability to emit electrons. I've found that the 215-A tubes will function quite well at about +0.75vdc filament voltage.

Waveform on Range B at 600 meters or 500kc VP/P=149mv

SE-1834 Circuit Analysis, Testing, Restoration Testing the functionality of SE-1834 is much more involved in that six WE215-A tubes are required for full operation. Point-to-point DCR testing has shown that both audio interstage transformers have good primary and secondary windings which is very helpful (and, yes, I do use that Triplett VOM for continuity testing as shown in the background of "The Test Set-up" photo above.) The 3rd RF transformer tests good for all four grid windings and for all four plate windings (it appears to be a vintage replacement.) The 2nd RF transformer has all four grid windings showing continuity but two of the plate windings are open (Band 1 and 4.) The 1st RF transformer has all four grid winding showing continuity but three of the plate windings show open (Bands 1, 2 and 3.) All grid windings in the three RF transformers are good (that's 12 grid windings total.) Of the twelve plate windings, five are open and will need to be repaired. Due to the failures in the plate windings involving all four bands, a bypassing of RF1 and RF2 would only leave RF3 in operation,...maybe okay for testing but RF1 and RF2 will have to be repaired for full operation. Due to the "iron core" type of RF transformers and the method of construction, any repairs to the windings will be difficult (but hopefully not impossible.) All other components of SE-1834 test okay as far as DCR continuity. One broken solder joint was found. It was a buss wire that connected F+ from the STABILIZER adjustable resistor to the 3rd RF transformer grid buss connections. There are four spring-clip type holders that seem to be for glass type cartridges for capacitors (or possibly resistors.) Two are for the Audio tubes and are from the plate to B- which would imply they are small value capacitors. One other spring-clip is connected from the detector grid to the secondary of the 3rd RF transformer. Since there isn't any connection to the detector grid except through this plug-in cartridge it must be the grid-leak (or a grid condenser.) The last spring-clip connects to the TICKLER terminal and to B- indicating this must be another small value capacitor to bypass any RF to B-. I found two, loose in the cabinet, glass capacitors that looked similar to large grid-leak resistors but were marked ".002uf" on the inside. These weren't installed but were wrapped in plastic and had been placed inside the cabinet. These are certainly for the small value capacitors needed. I'm missing a third glass cartridge for the last small value capacitor and a grid-leak resistor although there should be an associated small value capacitor which isn't in the circuitry so it must have been part of the plug-in cartridge. It is possible for the detector to function with just a capacitor however it will perform better with a high value resistor to B- (the resistor can be connected in parallel with the capacitor and "leak" through the secondary winding of the 3rd RF transformer to B-.) It appears that dismounting the tube socket chassis allows access to most of the components. To ease the process of disassembly and reassembly, a wiring assembly drawing (not a schematic) had to be made. Also, close-up photos using a Smart Phone really helps because the photos can be "super-enlarged" on the computer. RF Transformer Coil Rebuild - Actually, with very little disassembly, the RF transformer coil assemblies can be removed only requiring unsoldering three connections and removing five screws and nuts (straps with threaded holes for the transformer mounting.) I decided to remove and rebuild one RF coil assembly at a time since that will require the least amount of disassembly. With the other coil assemblies remaining in the circuit, I would have a reference for reassembly. The RF Transformer Coils are iron core with about .375" thickness of laminations. Unfortunately, the four coils appear to all share the same laminations. The coils themselves look like the typical audio transformer core only not nearly as wide and with a larger hole in the center of the core. Just to make taking the RF Coil assembly apart even more difficult, where the wires exit the wooden frame, those cavities are filled with sealing wax. It appears that the sealing wax is just in the cavities where the wires exit and not through-out the coils and laminations. Once the sealing wax is melted out, then the RF coil/transformer assembly should come completely apart. The 1st RF Transformer assembly has three out of the four Plate-to-B+ windings that are open and one Plate-to-B+ winding is okay. All Grid-to-A+/B- windings are okay. I tried a heat-gun to melt out the sealing wax but it isn't a narrow enough application of heat. A small soldering iron works better and is able to apply the heat directly where it's needed. Also, the soldering iron can heat just the individual wires to allow pulling them out of the sealing wax. Once the sealing wax is mostly removed and the wires are not being held by the sealing wax residue, the wooden frame can be removed. This exposes one side of the RF transformer assembly. The same wax melting procedure has to be performed to remove the opposite side wooden frame so that the entire laminations and the four RF cores are accessible. SE-1834 First RF Transformer Assembly - This is the B+ buss and the A+/B- buss side that's exposed. The other side is the Grid and Plate connections that go to the 4-position Band switch. The removed wooden frame is in the background. With both wooden frames removed, one can see that the individual coils can slide out of the laminations. Inside the center of each coil is a small iron lamination that's retained using shellac as a gluing agent. This small lamination provides the complete encirclement of each coil with iron laminations but also allows for easy extraction of an individual coil for repair (or replacement back in the 1920s.) The laminations don't have to have physical contact to provide a magnetic flux for proper operation. Although the RF Transformer coils look similar to audio interstage transformer cores, they aren't the same internally. The photo to the right shows the difference. The primary and secondary windings are spaced about .190" apart but are both wound on the same layer. Each layer builds from the center outward with just a few to several turns for each layer and for both the primary and the secondary. This continues building outward until the correct inductance is reached. Then the hook-up wires are soldered and the finishing wraps put on the coil. Primary winding wires exit on one side and the secondary winding wires exit on the opposite side. That's why when looking at the RF transformer coil, it looked like the wires were exiting from the center and outer edge rather than how audio transformer wires all exit from different layers from center to the outer layer. Winding these RF transformers is easy in one regard, each layer only has a minimal number of turns. On the other hand, one has to do two coils at the same time requiring two spools of magnet wire. In testing the DCR of the coils and it appears that the turns ratio is probably about 1:1. The only good coil in the 1st RF transformer is the LF coil and the primary and secondary both measure 4400 ohms. If the 1:1 ratio holds true for the other three coils then the next coil DCR is 2200 ohms, then the next coil is 750 ohms DCR and the high frequency coil is 350 ohms DCR. I double-checked these DCR reading by measuring the two remaining RF transformers and the DCR values were consistent at 4400, 2200, 750 and 350 ohms. After a thorough inspection, I think the easiest and best method of repair is to wind entirely new coils. Since both coils are wrapped the same on each layer, that is why the DCR is the same for both the primary and the secondary. However, there are some questions about the DCR involved,... SE-1834 high frequency 1st RF transformer core removed from the laminations. It's easy to see how the Primary and Secondary windings are on the same layer and that the coils are built from the center of the core out. Also note the size difference with the LF coil being the largest. Some Math reveals the Impossible - The resistance per foot of 38 gauge magnet wire is .66 ohms. To measure 4400 ohms, the length of wire necessary would be 6,666 feet and since there is a primary and secondary winding that would double to 13,330 feet. The weight of 13,330 feet of 38 gauge copper magnet wire would be around .6 pounds. It's physically IMPOSSIBLE for that much wire to be placed in the core of the largest of the cores and that core itself doesn't weigh even close to half-a-pound. 1922 Federal T&T plug-in RF Transformers were wound with resistance wire that allowed a typical number of turns to the windings to have a much greater DC resistance than expected. I scraped off the enamel coating on the RF transformer core's wire and it was silver color. I measured approximately 1.5 ohms for a 1" length and that would equal 18 ohms per foot. For 38 gauge resistance wire this is fairly close to the description of 38 gauge Ni-Chrome wire which is 12 ohms per foot (I measured the wire diameter using a dial caliper, so there could be a slight physical error. Maybe the wire is actually 40 gauge.) This makes the amount of wire necessary much more believable. 4400 ohms DCR would take 366 ft of wire and that's for the largest coil (732 feet for both the primary and secondary total.) For the highest frequency coil (smallest) that would take just 29 feet of wire or 58 feet total for the primary and secondary. The MAJOR problem is virtually no Ni-Chrome wire is available with an enamel-type (Foamvar now) of insulated coating. Insulated Ni-Chrome is a specialty type of resistance wire and priced well-into the stratosphere (how about $750 for 100 feet! That would be $4000 for the amount I need! It must be the cost of Foamvar.) I did find a cheap source of 38 gauge insulated Ni-Chrome wire but it was in the Ukraine and on eBay. The bargain-priced Ukrainian Ni-Chrome is $25 for 25 meters and I need 175 meters total (575 feet) and that prices out at about $175 and that includes shipping but Customs duty or tariffs are an unknown let alone what the delivery time would be. Also, I have to contact the seller to see if he can actually supply 175 meters (7x of what he's selling.) Not the Best Solution, but a Working Solution - Essentially, the need for insulated Ni-Chrome for the RF coils and its "specialty" status means another, hopefully temporary, solution is necessary. Luckily, the 3rd RF transformer is completely intact and can be used. I can disconnect the grid input wire from the 1st RF Amplifier tube and disconnect the 3rd RF Amplifier grid wire (that is coming from the 2nd RF Amplifier.) Then the grid wire that had been connected to the 1st RF Amp tube can be routed to the 3rd RF Amp tube. This would allow the SE-1834 to be used as a broadband four position single RF Amplifier stage, detector, heterodyne oscillator and two stage Audio Amplifier. This would end up with the SE-143 operating as a five-tube TRF receiver including the Heterodyne Oscillator (which is better than not operating at all.) If the bargain-priced 38 gauge insulated-coated Ni-Chrome wire works out then I can then go ahead and restore the 1st and 2nd RF transformer assemblies. Incidentally, I've come up with a method that would only require rewinding the open plate (primary) windings. The core could actually be bisected down the middle, separating the primary from the secondary. Then a new primary wound with the Ni-Chrome wire and that completed primary core (half) could be "grafted" back onto the secondary part of the core. This method also divides the amount of Ni-Chrome wire needed in half, that is, compared to if the core was entirely rewound (both primary and secondary windings.) The requirement of 575 feet (175 meters) of wire is based on using this solution. Implementing the SE-1834 Circuit Changes - All of the circuit changes implemented are easily reversible. I reassembled the 1st RF Transformer but didn't bother connecting up each of the cores. They are present, except for the highest frequency core, inside the assembly. All four of the cores will be available for rebuilding when the correct type of Ni-Chrome wire is found. I then reinstalled the 1st RF transformer assembly back into the chassis of SE-1834. I didn't bother with fixing the band switch contact arms for RF1 and RF2 since they aren't going to be operational anyway. I did realign the contact arms for RF3 so they make proper contact with operation of the band switch. Since RF1 was disconnected internally, I removed the B+ going the RF1. RF2 wasn't taken apart so I left the B+ connected there. I removed the flexible wire from RF3 grid and the flexible wire from RF1 grid. I taped the end of the RF1 grid wire. I installed a 2" flexible wire extension to the grid wire that comes from the RA input and soldered that wire to RF3 grid. That will have the RF tuned signal from the SE-143 connected to RF3 grid. This completed the circuit changes necessary for operation. Testing - I hooked up +2vdc to FIL+ and FIL- at which point the meter indicated FS +2vdc regardless of the filament adjustment pot (no tubes, no load.) I checked that I had +2vdc at all of the tube socket filament contacts. Next, I connected +40vdc to the B+ and B- and tested the tube socket plate contacts. The detector plate didn't have B+. The problem was caused by the very dirty and partially oxidized TICKLER terminals and the shorting strap. I cleaned all the metal parts with a brass bristle brush. When reassembled, I had detector plate voltage at the tube socket. I installed two 215-A tubes in the AF1 and AF2 amplifier positions. I connected a set of Baldwin Type C 'phones to the TEL terminals. I connected an audio signal generator set to 400hz to the plate of the detector tube socket (no detector tube installed.) This connection placed the audio signal going through the primary of the first AF interstage transformer. With +2vdc FIL and +40vdc B+ applied, I heard the 400hz signal coming through the Baldwin 'phones. This test showed that the audio section is working correctly. To test the detector and RF amplifier requires a modulated RF signal. I first needed to make up a grid-leak and a small value capacitor for the two clip connections for the detector "plug-ins." I installed two more 215-A tubes in the Detector socket and in the 3rd RF Amplifier socket. I used the HP606B to apply a 500kc (600M) RF signal modulated with 400hz to the Grid input terminal of the SE-1834. Voltage was applied and with the SE-1834 set on the 250M to 750M band, I heard the HP606B coming through the Baldwin 'phones. I tried the other three ranges and adjusted the HP606B as needed. All four bands worked. I moved the SE-1834 and the power supplies to the ham shack where the SE-143 was set up. I connected the SE-143 RA to top INPUT terminal on the SE-1387 and SE-143 RE to the SE-1384 bottom INPUT terminal. I shorted the SE-143 TICKLER terminals and placed the TICKLER COUPLING at MIN. I had the SE-143 set to 630kc (KPLY-Reno) so I set the SE-1834 band switch to 250M-750M and applied voltage. KPLY came in so strong, the signal was somewhat distorted. I made a few adjustments to both the SE-143 and the SE-1834 and that got the signal strong without distortion. I tried a few other daytime AM-BC stations and all were received easily. Next, I removed the jumper from the SE-143 TICKLER terminals and the shorting strap from the TICKLER terminals on the SE-1834. I used two wires to interconnect the TICKLER coil to the setup. Although there was an increase in signal, I couldn't get the detector to oscillate. The connection of RE from the SE-143 is to B-/A+ through the SE-1387 Coupling Coil and the SE-1834 STABILIZER variable resistance. I had the SE-143 connected RE to B-/A+ in my first setup and I couldn't get the UX-201A tube to oscillate either. Only when I connect RE directly to the A- terminal will the SE-143 detector oscillate. There's no way to make that connection using the terminals as marked on the SE-1834 BUT if I hook-up the SE-1387 Heterodyne Oscillator, I should be able to have a tunable heterodyne available. The gain of this setup with just one RF amplifier is certainly less than what it was originally (less selectivity also.) Still, it will drive a horn speaker to room volume on AM-BC stations and is extremely LOUD on 'phones. In fact, the AM-BC stations are too loud for 'phones so I set up the WE 10-D horn speaker if AM-BC is going to be tuned (only for test purposes.)

Using the SE-143 Receiver with the SE-1387 Heterodyne Oscillator and the SE-1834 RF Amplifier-Detector-2 stage Audio Amplifier

The key to getting the SE-1387 and SE-1834 combo working with the SE-143 is experimentation. Since there's absolutely no documentation on the SE-1387 or the SE-1834, I've had to rely on my circuit analysis, the implied connections from the arrangement of the terminals and one vintage photograph (the 1925 USN Shipboard Radio Room photo below) to theorize how the entire setup would interconnect and function. Then experimentation was necessary to see if theory could actually result in a complete working apparatus. Luckily, it did.

TESTING - To simulate an LF CW signal, I connected the HP606B to a 50' wire laying on the floor. I set the frequency to 300kc or 1000M with the amplitude set to 0.3vrms. The SE-143 was picking up this signal using the outdoor 250' end-fed wire antenna. Audio output was to the WE 10-D horn speaker. The carrier plus heterodyne was easily found and tuned for maximum. I keyed the output of the HP606B to see how true CW would have sounded and it was pretty nice. Stability of the heterodyne note is pretty good with maybe a few hz variance every so often. The heterodyne note quality was very good. Copying a true CW signal would have been easy.

Also tested reception over the air of Loran-E 100kc and WWVB 60kc. This required changing ranges on the SE-1387/SE1834 and the SE-143. Heterodyne tuning on Loran-E and WWVB along with over the air reception demonstrated that the combination was working on all tuning ranges. Although all of the "below 500kc signals" mentioned were audible through the WE-10-D horn, it was much better copy on these signals when using 'phones however any AM-BC stations tuned were "too loud" for 'phones (put the 'phones on the cheekbone in front of the ears for strong signals.) The WE215-A tubes seem to work best at about 75% of specified filament voltage, about 0.75vdc results in good performance.
 

OPERATIONAL NOTES - PHOTO RIGHT: The photo shows the SE-143 with the "Combo" tuned to and actually receiving WWVB 60kc or 5000M. The filament supply is set to +2.5vdc and, with the Filament adjustments on the "Combo," the five WE215-A tubes are drawing about 900mA (at their rated .25A each the total current would be 1.25A.) The FILAMENT meter on the SE-1834 reads +0.72vdc. The Plate supply meters each show FS at +20vdc for a total of +40vdc plate voltage. Note that Antenna lead wire is connected to the PRI LOAD COIL terminal and the ANT is jumped to GR. This connects the Primary LC for parallel tuning that allows actually tuning the Primary LC to resonance (below 100kc) for tremendous signal strength. Also note that, since the TICKLER isn't utilized in this hook-up, it's shunted and set to MIN. coupling. Antenna is the 250' End-Fed wire and the 'phones are Baldwin Navy Type-C.

Comparison of the Homebrew D-A to the SE-1387/SE1834 Combination Setup - While this homebrew regenerative detector and 2-stage amplifier works fine and I'm sure many MW signals could be found during the LW season at night, the regenerative detector is very fussy to adjust and requires keeping both the Primary LC and the Secondary LC tuned exactly. There's a lot of control manipulation required with a regenerative detector. It also helps to set the "Critical Coupling." I've tuned in everything from AM-BC down to WWVB on 60kc. Also, the MSK signal on 70kc and many carriers between 60kc and 70kc. Of course, Loran-E 100kc. All audio reproduction was using a Western Electric 10-D horn speaker. Tuning in low power stations like NDBs require using headphones for audio reproducers. While all strong signal stations can be tuned in and received over the horn speaker using the homebrew D-A, the SE-1387/SE-1834 combo is superior for reception with much better stability and no interaction. This is because the detector isn't regenerative, it's just a standard grid-leak detector. The SE-1387 provides the heterodyne necessary for CW reception and the RF amplifier combined with the two-stage AF amplifier is pretty hard to beat.

VLF Experiment tunes to NLK 24.8kc - I connected a 1500 turn honeycomb coil to the PRI LOAD COIL after undoing the shunt. I connected a 1000 turn honeycomb coil to the SEC LOAD COIL after undoing its shunt. Since I was using the SE-1387 heterodyne oscillator and SE-1834 as the RF amp, detector with 2 stage AF amp, a tickler coil wasn't necessary. I just set the two coils next to each other on top of the receiver with a slight angle between the coils for coupling purposes. I used clip-on test leads for the connections. This was just a test to see if the loading coils would allow tuning to the VLF part of the spectrum. I set the heterodyne oscillator to 15,000M or about 20kc. The USN Sub-Comm MSK stations operate from 19kc up to 25kc. I set the SE-143 inductance switches to maximum L. I had the Antenna connected for parallel LC on the Primary tuning. I switched on the power supplies to operate the SE-1387 and SE-1834. There isn't any calibration on the Secondary tuning for wavelengths below 6000M but the blank area above scale 6 could have been used for pencil notations when using loading coils. I could hear the heterodyne oscillator after I tuned the SE-143 to about mid-scale. After some primary and secondary tuning with some adjustment of the loading coil positions, I could hear the familiar sound of NLK 24.8kc from Jim Creek, Washington. NLK transmits a Minimum-Shift Keying or MSK type of signal that produces a "warbling" sound if there is an oscillating heterodyne to modulate the signal for audibility. NLK can run up to 1.25 million watts to a double horizontal "W" antenna that has its ten 5000' horizontal runs across a valley between two mountain sides in Central Washington. NLK produces a formidable signal in the Western USA. With a better setup for the loading coils I'm sure this type of longwave reception will become a much easier operation,...this was just an "clip-lead" type of experiment to see if VLF operation was possible.

Building a Replica Remler Duo-Lateral Honeycomb Coil Mount - Photo Right - I based the design of this Duo-Lateral coil mount on the one that can be seen in the U.S. Navy Shipboard Radio Room photo (in next section below) and on the photo of the Remler Duo-Lateral coil mount that's shown in the old 1970s Morgan McMahon book "Vintage Radio." I searched through my stash of vintage bakelite material to find appropriate thickness pieces. The vertical piece is .375" thick bakelite and the bottom is .250" bakelite. The vertical piece is mounted with large hex threaded (10-32) stand-offs (although the original Remler stand had round stand-offs.) The hex stand-offs were already nickel-plated and were vintage. For the actual coil mounts, I had a box of Remler Honeycomb coil parts and the box contained all of the pieces I needed to have a stationary Secondary Coil in the middle position and a "swinging" Primary Coil on the left and a "swinging" Tickler Coil on the right. The Remler coil mounts that "swing" have a hole through the side of the bakelite mount for mounting a round metal rod that's bent forward to act as an arm that allows moving the "swinging" coils with a minimal amount of hand-capacitance effect.

Since the low frequency coils are quite large (4" diameter) and fairly heavy, the vertical bakelite piece for the coil mounts has to set far back on the bottom bakelite piece to allow the front-heavy coils to be supported in a mechanically stable manner. The original Remler mounts didn't do this and were intended to be physically secured to whatever they were placed on with screws. I didn't want to do that type of mounting so I made the bottom deeper to allow the vertical piece to set back and have the coil weight supported by the extension of the bottom piece further forward. The wires hook up in the back of the vertical mount and are routed forward around the sides to connect to the SE-143 terminals. This hook-up can be seen in the USN Shipboard Radio Room photo below. I had to make the lever-arms for swinging the Primary and Tickler coils. I used 3/16" steel rods 8" long. I tapped the holes in the coil sockets and threaded the ends of the rods. I installed the rods and marked them for bending. The rods were unscrewed, bent and then reinstalled. I used 1920s vintage knobs for the ends of the rods. Next, the six wires were installed. These were vintage wires but they were all black insulation which is how the hookup wires appear in the USN Shipboard Radio Room photo. The wire ends were stripped and tinned for the best connections.

The SE-143 with SE-1387/SE1834 "Combo" and Long Wave Duo-Lateral Loading Coils on top. This setup easily receives NLK 24.8kc, NAA 24.0kc and NPM 21.4kc USN Sub-Comm stations. I can just tune WWVB 60kc at the top end of the range using these coils. Using the D-A Reg Det setup with the LW Coils I received NWC 19.8kc in Exmouth, Australia. I used the HP3312A Function Generator as a "marker" to confirm that I was tuned to 19.8kc.

Using Longwave Loading Coils to Tune VLF - The photo to the left shows the SE-143 with the SE-1387/SE-1834 "Combo" and the replica Remler Duo-Lateral LW Coil Mount on top of the receiver. The coils are 600 turn Primary, 1000 turn Secondary and a 1500 turn Tickler that isn't being used. With much better wiring to inter-connect the LW coils, I could easily tune in NLK 24.8kc and the signal was very loud. I tuned just a bit lower in frequency which requires keeping the Primary condenser tuned, to receive NAA 24.0kc in Cutler, Maine. NAA can run up to 2 million watts to an immense dual Trideco-umbrella antenna array but NAA usually runs about 1 million watts (500KW to each Trideco.) NAA wasn't as strong as NLK but it was still a strong signal that was easy to tune in. I installed the 1000 turn coil in the Primary position and the 600 turn coil in the Secondary position. I was able to tune in NPM 21.4kc from Hawaii. However, without a marker signal for reference, it's difficult to tell exactly which USN station is being received. Usually, NLK would be strongest, then NPM followed by NAA. NWC 19.8kc in Exmouth, Australia is only a moderate strength signal and NML 25.2kc in LaMoure, North Dakota doesn't seem to transmit as often as the other USN stations.

Using my General Radio Type 1000-A RF signal generator (which will actually output a sine wave down to 5kc) as a marker, I was able to confirm that NLK, NAA and NPM could all be tuned and received over the air. Also, using the GR1000-A, I could actually test the tuning range using the LW Loading Coils. The best frequency coverage was using the 600 turn coil for the Secondary and the 1000 turn coil for the Primary. The 1500 turn coil has too much inductance in either location, so it's an unusable visual enhancement for the Tickler position. The highest frequency that I could actually receive an identifiable signal was WWVB 60kc (10KW from Ft. Collins, Colorado.) The lowest frequency I was able to tune and receive an identifiable signal was NPM at 21.4kc (550KW to twin ground-isolated towers supporting top-fed dual radiators running to the helix house from Lualualai, Hawaii.) I think a more precise coverage would probably result in having a 750 turn coil for the Secondary, which would probably result in 50kc to 15kc tuning (just a guess.) The 1000 turn coil works okay for the Primary but another 750 turn coil would move the Primary tuning more to the center of the tuning range. These large 4" diameter honeycomb LW coils are difficult to find, so I'm still in the search mode for a 700 to 800 turn coil,...or maybe two. See NOTE 3.

NOTE 1: On using the Heterodyne Oscillator,...like any beat frequency oscillator, it's easily possible to use the oscillator to adjust the apparent received frequency. At high frequencies, 1kc of heterodyne only seems to change the CW beat note,...perceived as an audio effect. At VLF, 1kc of heterodyne action can substantially effect the tuning, changing for example 24kc combined with a heterodyne to produce a 1kc beat note can move the apparent received frequency to 25kc. When NAA, NLK and NML are all separated by less than 1kc, the Heterodyne Oscillator has to be carefully adjusted and monitored. Tuning in stations with the heterodyne oscillator turned off will result in more accurate tuning but often the desired station can't be heard unless there's a beat note present.

NOTE 2: One of the best improvements was to eliminate the clip-lead connections. I replaced them with 18 gauge wires that were twisted tightly where junctions were necessary before installing the terminal nut. The improvement in filament adjustability along with improved signal levels and especially in heterodyne action was dramatic. Clip-leads are for test setups and should be replaced as soon as possible.

NOTE 3: Using the Homebrew D-A with Regen Det and the LW Coil setup, I was able to receive NWC 19.8kc Exmouth, Australia. I substituted the useless 1500 turn Tickler coil with a 250 turn Tickler coil (4th largest I have) and it worked surprisingly well.

Vintage Photos of SE-143 and SE-1420 Setups with Various "add-ons"

Vintage photographs of early radio stations are always interesting but they are even more interesting if the equipment in the photo can be identified. I've provided as much information as I can as far as recognizable equipment, the frequencies being used and the various "hook-ups" being used. The first photograph is an SE-143-based station at NAA. It's an actual working environment and with the radio operator present. This "at work" photo was a real impromptu shot that is slightly over-exposed and the operator moved his head during the exposure. The second photo is an "equipment only" shot but the important aspect is that the photo is dated and it tells exactly where it was taken, NPX in San Pedro. It's an extremely large photo with lots of detail. The third photo is also of another station at NPX that used an SE-1420 receiver and SE-1000 amplifier. The fourth photo is a very informative photo of a USN shipboard radio room that has an SE-143 with a lot of "add-on" equipment shown. All of the various hook-ups are described in the text. This photo was taken with an excellent camera lens, it's superbly focused and, when the original is enlarged, the year on the calendar on the wall can be read. The last photo shows an SE-1420 receiver with some various "add-ons." This shot was probably intended to show the type of equipment being used at NAA at the time of the photo. It's a lot of nicely focused gear and when the original is enlarged the data plates on the equipment can be read.

U.S. Naval Station NAA - Ft. Myer-Arlington, Virginia
SE-143, SE-1071, SE-1000 Station

The photo to the left shows a standard SE-143 set up with the SE-1071 Audion Control Box and the SE-1000 Two-Stage Audio Amplifier. These two accessories were the most commonly used accessories for the SE-143, especially towards the end of WWI and immediately after. On the right side of the table is another SE-1000 and SE-1071. The LW Loading Coils are quite large in this setup. These coils appear to be "single layer" wound coils rather than "bank wound" or "honeycomb" coils which would be noticeably smaller in size. These LW Loading Coils have a set of tap switches in front of the coil to allow selecting various taps on both the primary and secondary. It's difficult to tell if the coupling can be changed but the reduced size of the upper coil seems to imply that it can slide into the lower coil and therefore increase the coupling. The coil assembly mounted to the wall is probably an antenna coupler. The lower area under the desk riser appears to have what looks like individual variable condensers but it's unknown exactly what their function would have been.

Note that the SE-143 is tuned to a rather high frequency. It looks like about 400kc.

This is a "non-posed" photo since the radio op moved his head during the exposure. Note the over-exposed ceiling lamp. Even though the lighting and focus aren't very good, this is an incredibly valuable historical document showing how radio equipment was set-up post-WWI.

Photo date is probably about 1920. At that time, the eagle on the left arm indicated a petty officer in a specialty section, which radio would have probably been considered. This photo is all over the Internet but I got it from navy-radio.com

NOTE: Navy Radio Station NAA was built in 1912. The station house is still used today by the Navy for administration work. The incredible 600 ft tower that was flanked by two 425 ft towers (called The Three Sisters) were razed in 1941 due to their proximity to the Washington D.C. airport. Prior to the razing, all radio equipment and communication duties were moved to USN Station NSS at Annapolis, Maryland

U.S. Naval Radio Station NPX - San Pedro, California  -  June 1920
SE-143, SE-1071, SE-1000 Station

The important aspect of this great photograph is that it's dated and indicates exactly where the equipment is set up. Obviously, the receiver is an example of the later SE-143 receivers. Note that the CRYSTAL-AUDION switch now has a third position, SEND. In addition to the third SEND position, the switch positions of CRYSTAL and AUDION have be exchanged (it's possible that this variation could be typical for Wireless Specialty Apparatus IP-500 builds.) Also, note that the buzzer push button is not the pearl button type but a different type with a black push button. The original photograph is very large (5000x5000mp) and that allows seeing all of the pencil marks on the dials and on the panel of the receiver (a lot of 'em.) Note that the INDUCTIVE COUPLING is at 90 while the TICKLER COUPLING is almost at minimum. The SECONDARY INDUCTANCE is on position 3 covering about 4000 meters to beyond 1350 meters or about 75kc to above 225kc up to about 300kc. The Secondary LC dial is set to the highest frequency possible on position 3 or around 300kc. The Primary LC is hooked up for series LC tuning and no loading coils are used.

Along with the SE-143 is the SE-1071 Audion Control Box with a Crystal Detector stand on top. Note that the Crystal Detector is connected to the CRYSTAL terminals on the receiver although the receiver is set to "AUDION" on the detector selector switch. Also, note the bent connection straps that allows the SE-143 to set in the corner of the table while the SE-1071 is against the wall. Next to the SE-1071 is the SE-1000 2-stage Audio Amplifier. It's position on the table next to the SE-1071 shows just how small the SE-1000 was. Interesting to see that nearly all of the wired connections come through the table top and the holes are grommet-lined. Telegraph hand keys, line relays with ceramic switches and then a sounder with resonator stand are to the right. Note that the paper on the wall above the hand keys is a list of the "Q" codes. Under the clip-held papers is a list of Morse code characters. This great photo is from a collection of 20 very large photos of NPX taken mostly in June 1920. I've cropped and compressed these two photos here but the full size photos can be viewed "large and not compressed" on: www.navy-radio.com  

U.S. Naval Radio Station NPX - San Pedro, California - June 1920
SE-1420, SE-1000 Station

This is another photo from the collection of 20 San Pedro photographs dating from 1919 up into mid-1920 that are on the www.navy-radio.com website. This radio setup was at the other side of the room from the SE-143 station. The receiver is the Wireless Specialty Apparatus Co. version of the SE-1420. This receiver had its own onboard VT regenerative detector so it didn't require the SE-1071 Audion Control Box. However, the station is equipped with the SE-1000 2-stage Audio Amplifier. All connections to both the receiver and the amplifier are routed through the table top using grommet-lined holes. As with the SE-143 receiver at the station, this SE-1420 has pencil marks and dial smudges galore. The receiver is powered up (the meter indicates filament voltage is present) and it's tuned to Secondary Inductance position 4 at letter designation "M" which was 900 meters or about 330kc. The wire antenna lead appears to be routed up the wall with at least one visible ceramic insulator. The 'phones appear to be Western Electric 509-W types. Once again, telegraph hand keys, line relays, ceramic switches and a sounder mounted in a resonator box. The typewriter isn't a "mill" because it only has nine keys on the upper row of keys and the "mill" typewriters had ten keys on the upper row.

In examining these photos, it looks like there was at least one more SE-1420 + SE-1000 station that had the SE-1000 on the left side of the SE-1420. This station was just to the right of the SE-143 station but out of the frame of the SE-143 photo. The station shown in this photo to the right was across the room opposite of where the SE-143 was set up. This indicates that at least three receiving stations were set up at NPX in June 1920. Also, it appears that a radio transmitter wasn't at the station,...at least, if there was one, it wasn't photographed. I suspect that NPX was a "receive-only" station that the USN referred to as a "Control Station." It looks like incoming radio messages were copied and then relayed via landline telegraphy to another USN facility.

U.S. Navy Shipboard Radio Room - ca. 1925
SE-143 Receiver, SE-1372 Heterodyne Osc., LW coils and SE-1834A RF amp/Det/AF amp

The photo to the right is extremely informative and shows part of a Navy shipboard installation (note the open porthole to the upper left of the photo.) This installation is using the SE-143 and on the top left of the receiver is the SE-1387 RF Driver (or a similar type like the SE-1372,) then a duo-lateral LF loading coil assembly (looks like a Remler Type) and an SE-1834A (no filament meter so it's the "A" version) on the far right.

Note that the SE-143 is set to "CRYSTAL" on the Detector Switch. It's possible to setup the SE-143 to connect to two different VT signal processing circuits selected by either CRYSTAL or AUDION using the front panel switch on the SE-143. The setup could use AUDION to route the Secondary LC from RA and RE terminals to the Heterodyne Oscillator and through its terminals to the SE-1834A RF amp, Detector and AF amplifier. A second setup could be selected with CRYSTAL with the connections to TEL #75 and DET #81 terminals to access the Secondary LC and then route these wires to the SE-1834A as a RF, Regenerative Detector and AF amplifier (and not using the Heterodyne Oscillator.) The external switches would connect or disconnect the TICKLER terminals on the SE-1834A as needed. In essence, using the CRYSTAL and the AUDION switch allows the SE-143 to work with two different setups, e.g., regenerative detector in one position and non-regenerative detector with heterodyne oscillator in the other position (USN and Maritime regulations would require that a Crystal Detector be available somewhere in the Radio Room.) Another possibility is that the SE-143 receiver is the later version with the AUDION-SEND-CRYSTAL positions and the receiver is actually set to AUDION.

The tuned frequency appears to be fairly high as indicated by the where the Inductance switches are placed. A close look at the SE-143 and it appears that both dial pointers are missing. If the op has the LW coils in the circuit, the placement of the Inductance switches won't have very much of an effect on the tuning since the LW coils have much more inductance than the SE-143 inductors. Since the LW Loading coil set includes a Tickler coil, one can assume that the SE-1834A is operated as a regenerative detector when operating below 50kc. Note that the SE-1834A has the TICKLER strap pointing up indicating that it's operating as a regenerative detector. That assumption then implies that the Heterodyne Oscillator might be a version that doesn't operate below 50kc (the SE-1387 will operate down to 10kc.)

Incidentally, the transmitter is a Quenched-Gap Spark Transmitter, probably one of the 2KW Navy Standard types. Several companies built these for the Navy, like Wireless Specialty Apparatus Co., Kilbourne-Clark Mfg., RCA, Federal Telegraph Co. and others.

The full-size version of this U.S. Navy photo is the "header photo" at the beginning of this write-up. That photo actually shows another USN Officer, the ship's Captain actually, standing behind the radioman (the radioman holds the rank of Lieutenant - note the "lightning bolts" above the two bars indicating "radio.") On the wall behind the Captain is a calendar. This photo is exceptionally well-focused with an excellent camera lens and, although partially obscured by the Captain, the year on the calendar can be read and is "192-" with the last digit not visible. A believable date for this photo would be around 1925.

This is the most informative photograph for showing the SE-143 and various "add-ons" in detail.

 USN Station NAA  ca. 1925

 (R to L) SE-1420 Receiver, SE-1372 RF Heterodyne Oscillator, SE-1597 Loop Antenna Amplifier, SE-1834A RF amplifier/detector/AF amplifier and a Receiving Antenna Coupler (being held by RMC Gilmour) 

NOTE: As can seen in the photo, none of these devices are interconnected implying that the equipment was probably arranged for the photograph and not necessarily that all of the equipment was "used" together.

U.S. Naval Station NAA - Ft. Myer-Arlington, Virginia  ca: 1925
SE-1420, Heterodyne Osc., Loop Antenna Amplifier, RF Amp/Det/AF Amp and a Large Antenna Coupler

Another setup is shown to the left, from USN station NAA. The receiver on the right side of the photo is the famous SE-1420, a single-tube regenerative detector receiver. Next is the SE-1372, a three band, possibly a specialized version of the SE-1387 with less heterodyne frequency coverage. The next unit is a Loop Antenna Tuner, the SE-1597. The left most unit is the SE-1834A with the "A" being the version without the filament voltage meter. That's quite a Loose Coupler that RMC Gilmour (RMC = Radioman - Chief Petty Officer) is holding though it's probably an antenna coupler of some sort,...note the similarity to the coupler in the older NAA photo above. A believable date for this photo would be around 1925.    this photo is found in many places on the Internet but I got it from navy-radio.com - I've cropped and compressed.

IF these accessory devices were to be used with the SE-1420 then some circuit changes would be necessary since the SE-1420 already has a detector. It would be possible to use the SE-1387 (or the SE-1372) by itself as a Heterodyne BFO ahead of the SE-1420 detector by connecting the SE-1387 output to the SE-1420 Antenna terminal (just wrapping the output wire from the SE-1387 around the Antenna lead wire should provide sufficient coupling or connecting to SEC COND and XTAL terminals can access the secondary LC directly.) Then the SE-1420's TICKLER/regeneration can be adjusted to the point just before the detector oscillates. The only thing accomplished would be to eliminate the oscillating detector and replace it with a heterodyne oscillator. Actually getting sufficient  regeneration for oscillation is highly dependent on the frequency tuned, the detector plate and filament voltages and the antenna used. The lower frequencies are particularly difficult to actually get the detector tube to oscillate. It's impossible to get the detector tube to oscillate at VLF unless loading coils are installed and the SE-1420 doesn't provide terminals for installing LF Loading Coils, so about 40kc is the lower frequency limit. A Heterodyne Oscillator would tend to make CW reception easier for a wider frequency tuning range.

The left-most unit is an SE-1834A and it might be possible to switch the SE-1420 control to CRYSTAL-RF AMPL to access the SE-1420's RF tuner section only by using the SEC COND, XTAL and TELEPHONES terminals and run the SE-1387 (as described in the preceding paragraphs) with the SE-1834A. No battery voltages would be required for the SE-1420 since only the Primary and Secondary LC tuners would be used. A lot of experimenting was certainly necessary when using these "add-on" pieces of equipment to achieve an actual functioning "upgraded" receiver.

SE-1420, IP-501 and IP-501-A Receivers
History, Design and Construction, Performance Testing

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 installations as late as 1940.

Wireless Specialty Apparatus version of the SE-1420, probably from a 1920 contract. Tunes from 300 meters to 7500 meters.  Serial Number: 270R

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 regeneration, called "TICKLER," was provided by a variometer that was built into the secondary inductor form. One stator coil of the variometer was connected to the secondary coil while the other stator coil was connected through the rotor to the plate circuit. The wiring connections provide for the proper phase reversal for coupling between the plate and grid circuits to occur. The adjustment of the rotor position within the variometer allowed resonating the L of the plate to the grid circuit for detector inter-electrode capacitance feedback and also simultaneously increasing the EM coupling by way of the EM field intensity of the variometer and its relationship to the grid tickler stator coil allowing positive detector feedback and oscillation at the proper physical adjustment of the variometer rotor.

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.

The photo to the right is 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) was used as a detector, while the Signal Corps preferred the Western Electric VT-1. There were many variations of the Moorhead ER tubes with different manufacturers building them from 1919 up to the early twenties. Both the VT-1 and the ER 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. Later SE-1420 receivers used the 201A and these tubes specify filament voltage (5vdc@.25A) The panel meters were changed from ammeters to dc volt meters as tube use evolved.

Upgrades - Apparently, many early SE-1420 receivers were rebuilt by the military as the receiver aged. This included upgrading the receiver to the SE-1420C or BC-131 configuration. This upgrading included adding a grid-leak resistor and capacitor assembly, usually mounted on the Secondary Inductor mount near the Tickler coil. Early versions of the SE-1420 relied on self-biasing of the detector tube and, although this does work, it requires fine adjustments of the filament and plate voltages for best results since there isn't a fixed negative bias source in the SE-1420. As vacuum tubes improved, the grid-leak arrangement worked better since it allowed for rectification (detection) and would "leak" off the excessive negative charges quickly though a high-value resistor. BC-131 receivers sometimes had an additional binding post added to the right-side vertically-aligned posts to provide access to the TICKLER coil.

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 circuit 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.

The IP-501 & Wireless Specialty Apparatus Company - 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 new commercial market, the designation of the receiver was changed to IP-501. A matching two-stage audio amplifier was now available, the Triode Type-B Amplifier (an updated civilian version of the SE-1000 that had been used with the SE-1420 although the Triode Type-B version increased the cabinet height to match the IP-501 cabinet height and changed the rectangular screened tube port for dual circular screened tube ports.) A Long Wave Adaptor was also available for operation at VLF frequencies. To accommodate the Long Wave Adaptor, hook-up terminals were added along the top of the panel to align with the LW Adaptor's terminals. Though early versions may have used ERs or VT-1s, after about 1923, the IP-501 receivers used UV or UX-201-A tubes.

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

RCA/WSA IP-501-A from about 1923 to 1925, early version with Telephone Condenser switch and nickel-plated binding posts
 

The IP-501-A, RCA & Radiomarine Corporation of America

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 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 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 users were certainly not as numerous as the general public 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 disappeared from the scene, apparently purchased or absorbed by RCA. It's likely that RCA also acquired the WSA manufacturing plant in the deal since all later IP-501s and IP-501-As were built still using WSA parts. From 1924 up to sometime in 1927, RCA apparently carried on building receiver using WSA components and selling those marine receivers. 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 marine operations and sales were then transferred to Radiomarine Corporation of America as a division of RCA. RCA had been operating many of the coastal wireless stations and providing "Radiogram" communications and those responsibilities were passed on to Radiomarine.
  

By the late twenties, the IP-501 family of receivers were beginning to show their age. The later versions eliminated some of the unnecessary or expensive circuits and parts but the basic style was still easy to recognize. Many receivers were still in use well into the late thirties. 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 at least a decade and a half. Advertising for RMCA was still using photographs of shipboard 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 this time.)
 

By 1930, RCA had 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 everything in radio in the thirties and forties. By the thirties, RMCA was running many of the coastal marine 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.

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

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 300 meters up to 7500 meters, or approximately 1000kc down to 40kc and the condenser is gear driven, (most receivers will tune 1200kc down to 37kc.)

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 and tickler built onto the secondary coil form. Variometer controlled regeneration relies on detector tube inter-electrode capacitance and the EM field coupling of the variometer rotor position relationship to the tickler coil (which is one of the stator coils inside 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 oscillation 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 upper frequency.) 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. Since the regeneration is tuned, lower frequency reception requires 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 total inductance in 90º of rotation (sign changes happen in quadrants) but, depending on the receiver, all "TICKLER" action is usually centered around 45º and increases to 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.

The "TELEPHONE CONDENSER" switch allows selecting various values of input capacitors to the RF pi-filter that is connected between the output of the TICKLER variometer and the audio output line. The RF pi-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. This function 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. RCA/RMCA eventually eliminated the TC switch, probably because of expense, potential problems and the fact that an optimum fixed-value capacitor resulted in effective static relief along with increased reliability by eliminating the switch.

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 mechanical buzzer that arcs and creates tremendous wideband RF. This is coupled into the antenna circuit with a brass sleeve capacitor on the wiring to the Antenna Inductance switch on SE-1420 sets and by a wire coil wrapped around the same wiring in the later 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. Additionally, a Long Wave Adaptor was sometimes used if operation below 40kc was needed. This unit sat on top of the receiver and its connections match the binding posts located at the top of the panel on the IP-501 and the IP-501-A (the Long Wave Adaptor units were not used with the SE-1420.) The Long Wave Adaptor had large inductors inside that when connected allowed the receiver to tune down into the VLF part of the spectrum.

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-1420 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 sometimes had a front cover that was held on with bale clamps. The ID tag is located on the side of the box and these are almost always missing. This was probably due to the "military surplus" regulations of the time that required all mil-tags to be removed before sale. Something about if the tag wasn't there then the unit wasn't stolen. This regulation may have also applied to commercial surplus. 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 40lbs 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 golden oak. Most BC-131 boxes are olive-drab paint. 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
1920 - Cross-licensing with GE-RCA group allows WSA to offer SE-1420 as commercial IP-501
1921 - Design of the IP-501-A
1922 - IP-501 and IP-501-A available from RCA acting as sales agent
1923 - Likely purchase of WSA assets by RCA.
1924 - SE-1420 contracts continue, National Electrical Supply Co. added to list of builders (after AMRAD's bankruptcy)
1925 - RCA continued production of the IP-501-A using Faradon and WSA parts.
1927 - Official formation of Radiomarine Corporation of America
1927 - IP-501-A updated - eliminated Telephone Condenser switch, bakelite capped binding posts
1927 - CGR-5A (SE-1420C) contract, National Electrical Supply Co., 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 is also a complex assembly.

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. To say that they were poorly documented would be an understatement. None of the schematics available are complete. Most will provide a general idea of how things are connected but details are certainly lacking. The various schematics are shown in several books, e.g., Elmer Bucher's book on Wireless Equipment or early editions of George Sterling's "The Radio Manual" or others, but all are incomplete schematics that are only provided as general information. The IP-501 schematic shown to the right is about as good as they get. Not a lot of details but it is basically complete and does show the connections to the complicated "Circuit Selector" switch. However, mistakes are common, e.g., the "Grounding Condenser" is not a variable, it is a fixed condenser. This schematic is good for the IP-501 produced around 1922. Earlier SE-1420 is similar but without the Long Wave Adaptor terminals. The later IP-501-A is a very different receiver but still a lot of this schematic is applicable. What one has to do is use good photos of the interior of original receivers combined with the information provided in the better schematics to ascertain what is correct for your particular receiver. This is assuming that your receiver needs to be restored and is missing some of the original buss wiring or original components. 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 are the most helpful to determine what is correct. Since the advent of eBay, which has now had many auctions/sales of SE-1420 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 very long.

Operator's manuals are around. Some are available on the Internet and some basic operating instructions are included in various books. Sterling's "The Radio Manual" - First and Second Editions have instructions for both the SE-1420 and the IP-501, along with the Long Wave Adaptor. However, these instructions are brief so they contain very few details. No details are provided about typical antennas for these receivers (although the 200' end-fed wire seems to be what is often specified.) The RCA and RMCA manuals are by far the best and most accurate.

Schematic for the IP-501 from "The Radio Manual" 1st Edition

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 (+ or - are used to indicate the increase or decrease of total inductance as the rotor turns inside the stator coils) as the pointer is advanced up the TICKLER scale. This results in the receiver requiring higher TICKLER settings as the wavelength is increased (lower frequency.) The correct wiring is the detector plate is connected to one coil of the variometer stator as the input. The grid circuit is wired to the other stator coil to provide the feedback path. The variometer rotor output (rotor-front) goes to the Circuit Selector Switch, RF pi-filter and on to the audio output and detector B+. To check that 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. 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 each extreme of TICKLER adjustment.

NOTE 1: Although you do get a change of total inductance through each 90º of rotation with a variometer, the two 90º quadrants in 180º of rotation are of opposite sign + or - (there is a mutual inductance change also.) When the variometer is operated in the opposite two 90º quadrants, the receiver will not regenerate on lower frequencies or will 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.

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 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 by RMCA, 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 late 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. This straightens the wire and slightly reduces it's diameter. It will make the buss wiring look very straight and professional.

Restoration of the IP-501-A

Back in 1979, I bought this IP-501-A from a ham friend, W7IND(SK,) who had traded a 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. My first restoration just got everything cleaned up and looking 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 good photograph of the inside of an original IP-501-A, something I had never seen before.

The 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 photos in the above sections for what the restored interior looks like.

My second restoration had been incorrect in several places and needed to be redone to be an accurate representative of the IP-501-A, both physically and operationally. I started to search for more parts for the new 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. It looked very close to original.  The Condenser Switch and assembly was rebuilt from correct vintage parts and then installed in a painted black, brass metal box I made. 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 is really 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 last restoration was done 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.

Restoration of the SE-1420

I bought this SE-1420 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. The seller described all of the modifications and indicated that no major holes were drilled and the coils and condensers were present. When the SE-1420 arrived I found he had described it very accurately. 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 in the late thirties and most of the modifications seem to date from that time period.

This SE-1420 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-260 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 is 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 bakelite platform and standard bayonet-twist type socket. The 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 socket due to a lack of detailed information. Over the past several years, I collected various vintage photos that showed the 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 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. I had to order the conical springs. The metal base plate, the stainless mounting studs, the brass thick spacers and the shouldered screws were made by a machinist. I made the bakelite parts. The tube pin contacts and chrome shell were found in the junk box.

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 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 very good photographs of original 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. Original examples have cotton wadding pushed into the springs, probably to reduce microphonics. 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.

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

A close up from a different angle showing the buss wiring, the TC condenser switch cover and the replica tube socket after installation. The original tube sockets had cotton wadding pushed into the springs to dampen movement and reduce microphonics.

"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 which was a grid-leak RC 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.

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.

Performance Testing 100 year old Shipboard Radio Receivers
 

Operating the SE-1420

The SE-1420 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.  NOTE: I performed this SE-1420 testing 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 which should boost the weaker signals,...maybe the noise too. I'd expect far fewer NDBs but there are other LF signals that I didn't test back in 2009. This testing would have to be conducted in the Fall when LW conditions are beginning to improve.

Operating the IP-501-A

The WSA IP-501-A during testing. 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.) 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 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. Unfortunately, the SE-1420 doesn't provide LF Loading Coil terminals so this type of hook-up can't be implemented for that receiver.

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
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.

IP-501-A Testing Results
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 an 87 year old three-tube regenerative receiver (now, 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 nowadays but there are several other LF signals to check on now that I didn't even tune to 17 years ago. In fact, ALS162, an 800KW PE Time signal out of France on 162kc (1800M) wasn't even operating then. Perhaps in the Fall, I'll conduct another IP-501-A reception test.)  

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. 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.

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.

Kilocycle to Wavelength in Meters Conversion Chart

* = Newly NDB heard

1. 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, modern modulated furnace blowers, 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.

2. 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 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. Most new street light installations are using LED type lamps and they don't seem to create RFI. Virtually none of the external sources can be "fixed" since the "correction" involves cooperation of the offending neighbor.

3. 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. 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 fairly high input impedance that was designed for a 200' end-fed wire antenna. The S-M Loop's 75Z input impedance is far too low to work well with early-twenties receivers. It's possible to use an "un-un" balun designed for high-Z end-fed wires and hook-up it up backwards so the loop antenna is fed to the Lo-Z side and the Hi-Z side goes to the receiver. I've successfully used this method with a Rycom LF Receiver that had a 3500 ohm antenna input impedance. Unfortunately, the large wire array antennas that can perform quite well in rural areas can't be used in metro-urban areas.

4. Antennas and Grounds - In metro-urban areas, with lots of major industry running 24-7 and millions of potential RFI creators, listening on MW and LW is going to be impossible. Going mobile to a rural area, operating on batteries and using some sort of "strung-up" 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 with an impedance matching "un-un" or other such Lo-Z to Hi-Z matching device. 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 with a non-ferrous metal with a small gap at the bottom of the loop. The RFI noise is mainly electric and vertically polarized. The SM Loop responds better to the magnetic portion of an electro-magnetic signal and in a 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 SM Loop signal just isn't strong enough, even though it's impedance-matched and the noise level is reduced. Another option is a remotely tuned loop. These are fairly large, maybe up to 10' in diameter, wire loops that are tuned with varactor diodes. They are easy to build and the pick-up loop (inside the tuned loop's field) can be designed to impedance-match the Hi-Z 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 and they do have a history of actually being used in the 1920s for direction finding applications. Many ground stations in the 1920s used Beverage Antennas. These were two-wavelength long antennas that were only about 10-15 feet off the ground. The Beverage was directional (in one direction only, if properly terminated) and did provide moderate gain at a low noise level but it also required substantial real estate for its installation. 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 (a really good ground that seeming went on forever although there wasn't a direct submerged ground per se.) 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" - RCA-Navy relationship, Creation of RCA by General Electric, Purchase of American Marconi by GE -  from Radio Broadcast - June,1922

6. "SE-143 Operating Instructions" - RCA manual from Nov 1936 - available online. George Sterling's SE-143 section in "The Radio Manual" First Edition is actually much more detailed in the operation of the SE-143

7. "IP-501-A Manual" - RCA/RMCA from 1938 - available online. This manual has details on setting "Critical Coupling" that greatly improves MW performance.

8. "The Radio Manual" - Descriptions and Operating Instructions for SE-143, IP-501/SE-1420, LW Loading Coils - by George Sterling, 1st Edition  1928. The 2nd Edition from Sept.1929 has the IP-501/SE-1420 but dropped the SE-143

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