Radio Boulevard

Western Historic Radio Museum


WHRM Radio Photo Gallery

Classic Pre-WWII Ham Gear

1928 - 1941



photo: W6NXW - Gus Gram, Los Angeles, California, ca: 1937 - Rcvr: Breting 14  -  Xmtr:  HB

Classic Pre-WWII Ham Gear - 1928 to 1941

Pilot Electric Manufacturing Company  -  "Pilot Wasp" - Model K-101

Though Pilot's advertising claimed they had been in business since 1908 and the company had used several different names during that time, "Pilot Electric Manufacturing Company" was officially founded in 1922 by Isidor Goldberg in Brooklyn, New York. Pilot Electric Manufacturing Company also claimed to be "The World's Largest Radio Parts Plant" in the twenties and they did build all of the parts supplied with their kits. Some of the famous employees of Pilot were Robert Kruse, Alfred Ghirardi and John Geloso. David Grimes was a Contributing Editor for "Radio Design" - Pilot's magazine. Though not the first Shortwave receiver kit offered by Pilot, the three-tube "Wasp" was certainly their first really popular Shortwave receiver kit. In 1928 the selling price was $21.75 including the coils. The "Wasp" was designed by Robert Kruse and Milton B. Sleeper. The plug-in coils selected the tuning ranges that covered 500 meters to 17 meters or about 600kc up to 17.6mc. A complete coil set featured five coils each with color-coded handles for identification. The three tubes were usually 201-A and the circuit used a regenerative detector followed by two stages of transformer coupled AF amplification. The kit included detailed instructions along with an assembly drawing. Builders were warned to adhere to the wiring layout shown on the drawing or performance would suffer. The circuit was built on a bakelite board for the chassis and a mahogany colored bakelite panel. The "Wasp" was introduced just as Shortwave Broadcasting was beginning to grow and everyone wanted to tune in to stations located in foreign countries. The "Wasp" was very popular and soon spawned a newer, more sophisticated successor, the "Super-Wasp."  


Pilot Electric Manufacturing Co., Pilot Radio & Tube Corp. - "Super-Wasp"  Battery Model K-110

 The four-tube "Super-Wasp" kit was introduced in early-1929 and featured a screen-grid tube for an RF amplifier along with regenerative detector and two-stage AF amplifier. The "Super-Wasp" kit sold for $29.50 including the five pairs of plug-in coils providing tuning coverage from 500 meters to 14 meters or about 600kc up to about 21.5mc. Detailed instructions, including a full size blue print, made assembly  relatively easy and assured that each "Super-Wasp" could perform pretty much as expected. Since these were kits though, build quality was highly variable and dependent on the assembler's experience. Pilot's magazine "Radio Design" was always including updates along with suggestions for improving performance, consequently "Super-Wasp" receivers are sometimes found today having modifications or non-original parts. The stock circuit used a type 22 screen-grid tube as an RF amplifier, a 201-A as a regenerative detector and  a 201-A tube as the first AF amplifier and a UX-112A as the second AF amplifier. The user could substitute a 201A for the last audio stage and reduce the plate voltage and bias voltage if a UX-112A was not available. To the right of the K-110 is one of the modular units Pilot called "Redi-Blox."  This one is a single-stage transformer input audio amplifier using a type UX-112A tube. This module could be added for a third audio amplifier stage if the user thought it necessary. Pilot offered "Redi-Blox" assembled modules in the late twenties to enthusiasts to help ease the mechanical side of kit building. Around the time that the "Super-Wasp" was introduced, Pilot changed the name of the company to "Pilot Radio & Tube Corporation" (April, 1929.) "Super-Wasp" receivers were quite popular and sometimes were found in ham shacks of the late twenties and early thirties. By today's standards, the "Super-Wasp" is a very primitive shortwave/ham  receiver but performance can be surprisingly good if the operator has patience and is willing to put in a few nights learning how the "Super-Wasp" works. All controls interact with each other making tuning sometimes tedious and demodulating SSB or CW signals requires the detector to be oscillating which increases the instability. However, patience will be rewarded and it is fun to use a 1929 battery-operated receiver to monitor one of the many AM ham nets on 80 meters, especially when running the audio to a vintage horn speaker - talk about "broadcast quality audio" - well, 1929 style anyway!  


Pilot Radio & Tube Corporation - A.C. "Super-Wasp" Model K-115

The improved "Socket-Power" A.C. "Super-Wasp" kit was available by late 1929 and sold for $34.50. The tubes used were a type 24A cathode and screen grid tube for the RF amplifier, a cathode type 27 for the regenerative detector and two 27s for the AF amplifier. All of the tubes operated on 2.5vac at 7 amps for the heaters and the K-111 power pack supplied all of the A+ and B+ voltages required. The lower right-hand switch was wired back to the K-111 to provide an "on-off" switch at the receiver. The first AF amplifier was a resistance coupled amplifier while the second AF amplifier was transformer coupled along with an output transformer. There was a considerable design effort put into the A.C. Super-Wasp to eliminate hum since most operation was going to be using earphones. Hum reduction was one of the reasons for the RC coupled AF stage. Pilot also stipulated that only their own Pilotron tubes would perform correctly in the A.C. "Super-Wasp."  Pilot plug-in coils are used for five tuning ranges covering 600kc up to 21.5mc. Shown to the left of the K-115 is the K-120 Audio Booster Unit, another Pilot module (though it is not called "Redi-Blox") for builders, that could be used if loud speaker volume was desired. All of the Pilot "Wasp" and "Super-Wasp" receivers found today will vary greatly in the quality of workmanship. Since these receivers were kits, the assembler may have had little or no experience in soldering, wiring or mechanical building. As a result, don't be hasty to judge a poor performing set as a "bad design." Check the receiver over carefully. An inspection of the soldering will usually be a clue into the level of workmanship you will encounter in your receiver. When everything is correct, the Pilot "Wasp" and "Super-Wasp" receivers are fine performers considering their vintage and a lot fun to use.  


National Company, Inc. -  SW-5 "Thrill Box"

The National Co. started in business manufacturing toys and parts in 1914 (as the National Toy Co.) By the mid-twenties, National Co., Inc. had long ago dropped the "toy" from their name and was supplying parts for the Browning-Drake BC receiver kit and also started producing radio parts. Mechanical Engineer James Millen joined the company as General Manager and Chief Engineer in 1928. Millen was a Stevens Institute graduate and an enthusiastic ham so it was natural that he guided National into the ham/shortwave receiver market. This move happened to coincide with the new and developing shortwave broadcasting which was becoming popular with a new audience, the "shortwave listeners" or SWLs. National introduced the SW-5 "Thrill Box" in 1930. The name "Thrill Box" implied how exciting it was for the SWLs to receive foreign broadcasts direct from around the world. Though primarily designed for the SWL, the SW-5 could also be found in many ham shacks in the early 1930s. It was an expensive receiver with selling prices usually over $100 with the power supply. Robert Kruse, of the Pilot Wasp and Super Wasp fame, was involved in some of the design work in developing the SW-5 through his laboratory in Hartford, Connecticut and with several visits to National's lab. The circuit was a five tube receiver using a regenerative detector (24-A) with TRF stage (24-A,) audio driver (27) and P-P audio output (2-27.) The coil sets initially covered 1.5 to 30MC in five sets but eventually several other coil sets were added along with bandspread coil sets. The first coil sets were color coded for identification. The receiver was powered by a separate power supply that provided the 2.5vac filament voltage and approximately 180vdc B+. The tuning dial was illuminated and projected onto a frosted viewing screen. The left hand control is the regeneration and the right hand control is an antenna trimmer adjustment. There was a "Battery Model" SW-5 available and a special "Low Drain Battery Model" that used 2-volt tubes that ran on an air-cell battery that was supplied with the receiver. There was also a "Special Broadcast Model" that had P-P 45 tubes in the audio output. Early SW-5 receivers may have been available as a kit similar to the Pilot Wasp sets. Some National receivers (SW-5 and SW-3 mainly) will have a decal or label stating that the unit was built at Jackson Research Laboratory, however this was a company that was solely owned by National and was located adjacent to the National plant. Labeling receivers as built at Jackson Labs was a form of product protection that was the result of a broad suit brought against all radio manufacturers by Cardwell sighting the use of their variable condenser patent. The suit was not successful but National kept the Jackson name around for a while afterwards.


National Company, Inc.  -  AC SW-3  (AC Version)

National introduced the three tube SW-3 in 1931. It was a regenerative detector with RF amp and AF amp utilizing plug-in coils. There was an AC model that ran off an accessory National power supply and a DC model that was operated with batteries. The DC model also had a switch under the lid to disconnect the A battery. James Millen and the National engineers put considerable effort into the SW-3 design to achieve maximum performance in a three-tube regenerative receiver. Shielding was carefully developed as was the coil design to allow both general coverage coil and amateur bandspread coils to be used. The end result was a little receiver that had amazing capabilities and was very stable at the point of oscillation. The SW-3 had a long production life and was produced in fairly large numbers. Coil sets were available for a wide range of frequencies from longwave to 30MC, along with the bandspread sets for the amateur bands. Later, the SW-3 became so popular as a stand-by receiver that National even offered it after WWII for a short time as the SW-3 "Universal" using three octal tubes. Parts and coils were available from National up well into the fifties. Probably the best testament to the SW-3 performance is in a photograph that is in a mid-thirites QST showing a ham station that used a full-size rack Collins built transmitter along with the station receiver - an SW-3 - certainly not typical but it says something about the SW-3 performance capabilities.


Hammarlund Mfg. Co., Inc.  -  Comet Pro with Crystal Filter
Eastern Radio Specialty Company - PEAK P-11 Pre-selector

Oscar Hammarlund immigrated from Sweden in 1882 to work for the Elgin Watch Company. In 1886, he became Superintendent of Western Electric's Chicago plant. Six years later, Hammarlund started working for the Gray National Company. His main project there was the Teleautograph machine. In 1910, Hammarlund founded his own company, The Hammarlund Manufacturing Company. Initially, the company built gadget-type devices but soon became involved with Western Union call boxes. An interest in wireless led the company into the radio component business and their variable condenser designs became an industry standard. In the mid-1920s, Hammarlund formed a partnership called Hammarlund-Roberts Co. specifically to offer kits for AM Broadcast radios using Hammarlund parts. By 1930, home radio technology had evolved to the point where kits were no longer practical or popular and Hammarlund-Roberts went out of business. That didn't affect Hammarlund Mfg. Co., Inc. since they were ready to enter into the shortwave receiver market with the introduction of their new Comet All Wave Receiver, a superheterodyne receiver, in 1931. Before the Comet was introduced however, Hammarlund offered a three-tube shortwave receiver as a kit. It was patterned after the Pilot Wasp and its sales most likely gave Hammarlund an interest in entering the shortwave receiver market. With the Comet's 1931 introduction, Hammarlund decided to offer a real improvement to the typical shortwave receiver of the day. At the time, the majority of hams and many professionals considered the regenerative detector (with TRF stages proceeding it) to be the most sensitive type of receiver. It had a very low noise figure and with the proper antenna and operator skill, reception results could be amazing. The superheterodyne on the other hand, while fine for broadcast reception, was considered too noisy and not sensitive enough for acceptable shortwave performance. Hammarlund hoped to prove that with careful design and quality construction a shortwave superhet could easily outperform the regenerative receivers in every comparison. 

Arguably, the Comet and its later successor, the Comet Pro, changed how SWLs, Hams and Professionals listened to shortwave signals. It was the first successful commercially-built shortwave superheterodyne offered to the communications receiver market (ham or professional.) Hammarlund advertised the Comet Pro as "The World's Finest Shortwave Receiver" and it certainly was built with high quality parts and high quality mechanical assemblies. Performance for the time was superb. The first versions of the Comet Pro (actually the Comet All Wave Receiver) used 24A, 35, 27 and 47 type tubes in an eight tube circuit that had no RF amplifier and utilized two unshielded plug-in coils - WL = Wave Length (mixer) and OSC = Oscillator - to change tuning ranges. The receiver was sometimes installed in a console cabinet. The receiver had a built-in power supply (with type 80 rectifier,) used a field coil speaker and came with a set of four pairs of coils covering 250M to 16M. An optional AM BC band (240-550M) coil set was available. The plug-in coils were wound on ceramic forms and had wooden handles for easy removal. Early table top cabinets were made of wood (painted black) with a metal front panel. In 1932, the audio output 47 was changed to a 27 and the field coil speaker connection eliminated. An earphone jack was provided in parallel with the audio output that was a direct plate connection. This implies that an audio output transformer would still be used at the loud speaker or that an input transformer would be used for the sometimes required external audio amplifier. Individual shields for each plug-in coil were added to this version. The OSC coil wiring was changed at this time. Additionally, "Pro" was added to the Comet name, implying that the receiver had evolved into a "professional level" of quality and performance and, by January 1933, the Comet Pro was fully a shortwave communications receiver. The tubes had been changed to type 57 and 58 types along with the addition of an audio output transformer to couple the 2A5 audio output to a 4000 ohm Z load - usually a loud speaker with matching transformer. The new audio output transformer also had a tapped winding for the earphone output. The antenna input was changed to allow a dipole feed line to be used and the WL coil's wiring was changed to accommodate the new antenna connections. The standard cabinet had been changed to an all-metal construction, however the wooden table top cabinet was still available on request. Later in 1933, a crystal filter option was added, then a 10M coil set option and finally, in Sept.1933, an Amplified AVC option was offered requiring the addition of a 2B7 tube to the circuit bringing the tube count up to nine. The "arc" dials set the WL and OSC condensers and then bandspread (the vertical dial) is used to tune in stations around the general settings of the WL and OSC condensers. The bandspread dial is illuminated and projected onto a frosted viewing window. The BFO adjustment is a "swing-arm" lever accessed under the lid of the cabinet. The Comet Pro listed for $150 not including tubes but usually sold for around $115 complete from discount dealers like Leeds. The usual sales procedure was to offer the Comet Pro chassis and then add options like the metal cabinet, Crystal Filter, AVC and tubes which then pushed the selling price up to around $150. Production continued up to early 1936. Hammarlund referred to the Comet Pro as a "Professional Receiver" and it was indeed used by many professionals, both military and commercial. It was also taken on several expeditions to the Arctic and Antarctic. The Comet Pro was also popular with amateurs and could be found in many ham shacks in the thirties. For its time, the Comet Pro was a first-class superheterodyne receiver that was well-built and performed quite well when compared to its early competition that was mostly composed of homebrew regenerative TRF receivers.

Eastern Radio Specialty Company was located in New York City and built many different kinds of ham accessories during the mid-1930s. Their brand name was "PEAK" and the P-11 Pre-selector was probably their most successful product. The P-11 used two type 58 tubes as TRF amplifiers. The tuning range was from 200 meters down to 14 meters (1.5 to 21.5MC) in three tuning ranges using built in coils. The P-11 had a built-in 2.5vac transformer to supply the tube heaters and the dial lamp with power but B+ had to come from the receiver. This was usually easy to tap into and the current draw of two RF amplifiers was going to be minimal. The circuit used electron coupled variable regeneration for its gain control (left knob.) The power on switch (right knob) also controls the routing of the station antenna as either bypassing the P-11 in OFF or through the P-11 when ON. The PEAK P-11 listed for $33.00 but, if the purchaser was a licensed ham he was automatically given a 40% discount from Eastern Radio Specialty, net price was then $19.80. The P-11 was first advertised in December 1934 QST. 


National Company, Inc.  -    RHM, AGS, AGS-X

The very rare (but equally famous) National Company's AGS receiver had its origins with their Department of Commerce Airways Receiver, the RHM (shown in photo below) The RHM was designed to supply "state of the art" receivers for airports in 1932. At the time, airports and air navigation were both growing and developing. Communications between pilot and tower required the best equipment and air navigation, including the various airways remote beacon stations, also needed improved communications equipment. National was given the contract for the ground receivers, General Electric was given the contract for the ground transmitters and Aircraft Radio Corporation was given the contract for airborne communications equipment. National was going to build their first superheterodyne to fulfill this contract and it seems likely that Herbert Hoover Jr. and his West Coast design team would be involved in some of the electronic engineering work of the RHM. National provided the mechanical engineering and the ability to produce the receivers in the quantity required. The RHM used nine tubes and tuned from 2.3mc up to 15mc. Most airport communication AGS installations also included a Type 58-C Monitor Receiver that allowed receiving two separate signals simultaneously. The RHM rack also included a dual power supply, panel rack holder for the spare coils and a rack mounted loudspeaker.

As mentioned, the RHM was National's first superhet but only a handful were built. To take advantage of the prestige the Government contract had given them (and to profit through additional sales to the general public,) National adapted the RHM receiver for commercial and ham use and dubbed it the AGS. It was an expensive receiver selling for $265 (with all accessories) in 1933. Frequency coverage was improved to allow better coverage of the ham bands, 1.5mc up to 20mc. The RHM had used first class materials and components throughout and the AGS was built to the same specifications resulting in the same high performance and reliability that the RHM had. National's advertising implies that after the initial DOC contract was fulfilled with RHM receivers, National continued to supply AGS receivers to airports and other commercial users from probably late-1932 up to the introduction of the HRO receiver in October 1934 (first deliveries were in early 1935.)

There were several variations throughout the AGS' short, two-year production life, mostly involving tube types and calibration procedures. The most significant improvement was the "Single Signal" AGS-X that was designed specifically for the affluent ham market (not heavily populated during the Depression.) The installation of the Lamb Crystal Filter allowed the operator to narrow the receiver IF passband considerably to improve copy in the congested ham bands. Also at this time, National started to offer ham bandspread coils for the AGS that allowed tuning the 160M, 80M, 40M and 20M ham bands spread between "20" and "120" (100 divisions) on the Type N dial (scaled 0 to 150 with 270º rotation.) Air trimmers replaced the old compression types used in the IF transformers by mid-1934. By late-1934, even 10 meter coils were being offered for the AGS.

Not all airport users were satisfied with the RHM-AGS with some airlines complaining that the receiver was not advanced enough. In response, National provided an improved RHQ-AGU version with all three coils ganged together to allow easier band changing. Frequency coverage on the RHQ-AGU was reduced to 2.5mc to 6.5mc and only two coil sets were supplied with the receiver. The RIO-AGL version was a medium wave and low frequency receiver that tuned from 160kc up to 630kc in two band switched tuning ranges. The circuit was a TRF receiver with tracking BFO. All of these versions were produced in 1933 through 1934 (go to "Commercial & Military Radio Gear" for more info on RHQ, RIO, RHM receivers.)

The HRO receiver was in the design-phase in the late-summer and fall of 1934 and, with its introduction in October 1934 (and availability by March 1935,) the AGS receivers became obsolete commercially. The AGS-X was available from Leeds at this time (early 1935) for only $123. Although the AGS-X was a great receiver in 1933, the HRO receiver's outstanding performance had antiquated the AGS-X in a little more than one year's time. 

photo above: AGS-X sn: F-151 from 1934. This receiver has its complete set of 27 coils. 15 general coverage coils for five ranges from 1.5mc to 20mc and its complete bandspread coil set for 160M, 80M, 40M and 20M coverage (12 coils.) The second coil holder is mounted on top of the rack. The Lamb crystal filter uses a 500kc crystal (as does the FBX receiver) to match the IF. The AGS-X also moved the BFO frequency control from inside the receiver to the front panel. AGS-X  F-151 has the air-trimmers for its IF adjustments indicating its a late-production receiver. I built the metal frame, table top rack based on one pictured in a ham station photo (with AGS-X receiver) in a 1934 QST magazine. 


Radio Manufacturing Engineers, Inc.  -  RME-9D

Radio Manufacturing Engineers, Inc. started in business in the early thirties, founded in Peoria, Illinois by two hams - E. Shalkhauser, W9CI and Russ Planck, W9RGH. Their first receiver, the RME-9 was designed in 1932 and was on the market by 1933. The RME-9 was a nine tube receiver with a single airplane-type tuning dial and an R-meter for measuring relative signal strength. The RME-9 featured a tuned-RF stage, two stages of IF amplification and a built-in power supply. The receiver was compactly-built onto a stout chassis made out of aluminum extrusion with the overall size of the receiver being quite small (19"W x 9"H x 10.5"D.) After some months of production and about 100 receivers produced, RME revamped the "9" and introduced the improved RME-9D. The RME-9D incorporated electrical bandspread and thus used two airplane-type dials with the R-meter between the two dials. Nine tubes were still used since the basic design remained unchanged. Five tuning ranges were provided with frequency coverage from .54mc up to 23mc. The tubes used were 58 (4), 57 (1), 2B7 (1), 2A5 (1), 24A (1) and 80 (1.) . Selling price was usually around $112 from discount houses.

The RME-9D was produced from late-1933 up to the introduction of the RME-69 in November 1935. There are some minor variations that are encountered with different types of knob sets being the most common. This especially relates to the tuning knobs with the large "RME-69" type tuning knobs often found on late versions of the 9D. Like many "Depression Era" receivers, it is common to find examples of the RME-9D with modifications added. The tuning and bandspread dials are relatively small and the nomenclature is miniscule and difficult to read but the dial illumination does help. For its time, the RME-9D was a first-class receiver that introduced what became the "basic necessities" for amateur radio receivers - built-in TRF stage, Carrier Level meter, panel operated BFO, Crystal Filter and Bandspread tuning. Although not necessarily the first receiver to incorporate any of these individual features, the RME-9D was the first receiver to use all of the features together as "standard equipment" and with no external assemblies necessary other than the loudspeaker. This rapidly became more-or-less "the standard" for all communications receivers for the next two decades.

The RME-9D shown in the photo is an all-original, late production version with a serial number of "431." RME receivers had a paper label on the bottom of the cabinet with the calibration date hand-written on it. The date on this receiver's tag is 9-12-1935. This is about two months before the introduction of the RME-69. Since this receiver is very late in the RME-9D production and has a serial number of 431 one can infer that the total number of RME-9D receivers built is probably around 500. The scant number of RME-9D receivers encountered today seems to confirm that production levels were very low.

RME-9D Speaker - The RME speaker housing was an unusual trapezoid shape that allowed for a bench corner location to be used for the speaker and then rectangular equipment cabinets could butt against the speaker cabinet sides. The speaker utilized was an eight-inch Rola PM speaker with a large "wrap-around" magnet support structure. The transformer is a matching transformer that provides a 4000Z for the receiver output transformer impedance and an eight ohm impedance for the speaker voice coil. Luckily, a date is ink-stamped on the speaker frame - JUL 9 1935


National Company, Inc.   -  FB-7, FBX, FBX-A 

In March 1933, National introduced the FB-7, a seven tube scaled-down and economically-built version of the AGS, offered so hams could buy a superheterodyne at a realistic price, (about $65 with accessories.) The FB-7 eliminated the RF amplifier and the AVC circuit of the AGS. Additionally, the 6.3 volt tubes of the AGS were replaced with 2.5 volt tubes in the FB-7. The extensive use of aluminum found in the AGS was replaced with sheet metal chassis and cabinet in the FB-7. The receiver used plug-in coils that are similar to the AGS coils. There were general coverage coils available and the ham could purchase a bandspread set of coils for 160, 80, 40 and 20 meter coverage. The BFO frequency control is a knob on top of the BFO coil can and is accessed under the lid. The FBX model added a crystal filter to the receiver with the controls accessible on the right side of the receiver cabinet. The FBX came out after James Lamb's article in QST about Single Signal receivers and crystal filters. A matching National pre-selector was available, the model PSK, that added a TRF stage to reduce the image problems but it required its own set of plug-in coils. The PSK was usually bolted to the right side of the FB-7 using standoffs - long standoffs if it was an FBX so the operator could have access to the crystal filter controls. Though many hams preferred using earphones, the FB-7 would drive a loud speaker quite well with the proper power supply. At least three different models of AC power supply were offered that could operate any of the FB-7 receivers but the 5897AB was recommended since it provided sufficient B+ voltage to allow the type 59 audio output tube to develop sufficient power to drive a loud speaker - about +240vdc. Most of the 5897AB power supplies that were sold with FB-7 receivers have a tag on top stating the the 5897AB was "designed especially for the FB-7." An "A" suffix to the FB-7 or FBX designation denotes the use of National's improved IF transformers that utilized air-spaced trimmers rather than compression trimmers. The receiver shown is an FBX-A from 1934. The FB-7 and its variations were very popular and found in many ham shacks in the mid-thirties.


Patterson Radio Co.  -  All Wave 10, PR-10 & PR-10 Pre-selector

Emmitt Patterson started Patterson Electric Co. in 1920 but renamed the company in the mid-twenties as Patterson Radio Company and began selling radios as a dealer. Around 1930, Patterson began building his own All Wave entertainment radios at the Gilfillan plant in Los Angeles. Patterson decided to enter the short wave amateur communications receiver market in 1933. Introduced in May 1933, the PR-10 was designed by Engineer Ray Gudie and featured a 10 tube circuit with R-meter, IF gain control (no RF amp), single 59 audio output built onto a chrome plated chassis. Performance was very good (especially for 1933-34) but by adding the PR-10 Pre-selector, with its two RF amplifiers, one could have a first class receiver. The initial models were slightly different and were designated as the "ALL-WAVE 10." The AW-10 didn't have a chrome plated chassis or the Manual Gain control (the AVC was always on - like a broadcast radio.) The AW-10 was probably produced for a few months before it was replaced with the redesigned version designated the "PR-10." The updates included the ability to disable the AVC allowing control the front end gain manually. This was particularly necessary for good CW reception and, at the time, virtually all ham communication was by CW. Other upgrades that were incorporated by 1934 were the reduction of the BFO coupling capacitor value to allow more sensitivity for CW reception and changes in the AVC time constant capacitor. With the designation PR-10, the chassis was then chrome plated. The PR-10 Pre-selector didn't change during production although there are some variations in coil diameter and under chassis component placement depending on early or late production. Like other West Coast radio builders, Patterson's documentation was never updated therefore the "one and only" schematic has several errors when compared to the actual production models.

The Patterson PR-10, along with the RME-9D, was one of the first communication receivers to offer a carrier level meter, band spread tuning, band switching (rather than plug-in coils,) stand by switch and built-in power supply. The only "standards" lacking were a crystal filter, a front panel frequency control on the BFO (the frequency control was under the lid) and a tuned RF amplifier. The latter was available if the Pre-selector was used. Overall, the PR-10 was an excellent performer that was reasonably priced and was found fairly often in ham shacks during the thirties, especially in the west.

The PR-10 listed for about $120, though most dealers sold the PR-10 for $70. According to Patterson, total production was around 70,000 receivers - an incredible claim. Supposedly, the majority of production was sent overseas to Asia which could account for the relative scarceness of the PR-10 today. The serial numbers seem to indicate a different story however as it is difficult to find a PR-10 with a serial number higher than 10,000.

All Patterson receivers were built at the Gilfillan Bros.,Inc. in Los Angeles, since Patterson did not have an RCA superhet license*, (see note at bottom of page regarding Gilfillan and their licensing relationship with RCA.)

The first communications receiver I owned (in 1965) was an old PR-10. Unfortunately, I decided to replace the 58 and 57 tubes with metal octal tubes, hoping for better sensitivity. The end result was a receiver that was basically non-functional! In 1985, I obtained another PR-10 and this one I restored correctly. It appears in Ray Moore's "Communications Receivers" Fourth Edition. The PR-10 shown in the photo above is the third one I've owned having purchased it from a museum visitor in 2005. It's had a long, well-preserved life having spent all of its time in Nevada. I fully restored this third PR-10 and the Pre-selector in 2016 in order to write a comprehensive web-article on Patterson Radio Company and the PR-10.

 For the ultimate information source on the Patterson PR-10 and matching PR-10 Pre-selector, including LA Radio Manufacturing history, Patterson history, PR-10 circuit and schematic analysis, serial number analysis, restoration and performance data, go to

"Patterson Radio Company - PR-10 Communication Receiver and PR-10 Pre-selector" - link below in Navigation Index


W7FM - Homebrew Transmitter-Receiver (TX-RX)

Some homebrew ham equipment was so well-engineered and so well-built that in some cases it's difficult to image that the gear isn't commercially built. It's extremely fortunate that some former owners have had the foresight to save and preserve these superior examples of amateur engineering. The W7FM Transmitter-Receiver is an amazing example of efficient packaging and shows the creativeness that was necessary during the Depression to build quality, compact, useable gear. W7FM, Don Thorton of Spokane, Washington, decided to build a two-tube regenerative receiver and a four tube (crystal controlled oscillator, buffer and parallel power amplifier) CW transmitter both with their own individual AC power supplies. Not particularly unusual in the early thirties. But how about installing everything into a 1927 Kemper Radio Company K-5-2 cabinet. The original Kemper K-5-2 was a portable five tube battery operated TRF radio in a leatherette covered wooden box that featured a removable front cover and removable back cover. W7FM built the two AC power supplies into the lower section of the K-5-2 cabinet where originally a folded horn speaker and battery storage was located. In the upper section of the cabinet as viewed from the rear (shielding removed for photo) on the right is the two tube receiver and to the left is the four tube transmitter. What is amazing about the packaging is that full shielding was accomplished by building the entire TX-RX into a metal box that fits exactly into the Kemper K-5-2 cabinet. The entire receiver and each section of the transmitter are contained in shielded compartments.

Looking deceptively light-weight, this TX-RX runs the scales up to an incredible 70 pounds! Full metering is provided with three panel meters. Six plug-in coils are required with two needed for the receiver and four for the transmitter. There are two complete sets of coils that were built for the TX-RX. Behind the speaker grille (with the "W7FM" embroidery) is an armature-pin speaker for receiver output. Separate receiver and transmitter antenna inputs are used. The receiver uses a type 27 for the regenerative detector and a type 47 for the audio output. The transmitter uses a 59 crystal oscillator, a 46 buffer stage and a pair of 45s in parallel. A hand-drawn schematic of the transmitter shows parallel 10s but Don Thorton probably decided that the 7.5vac filament voltage required for the 10s was impractical and went with 45s to keep all of the filament voltage requirements at 2.5vac. An 83 is used for the transmitter power supply rectifier and a type 80 is used in the receiver power supply. Note that the receiver power supply is built from old RCA Radiola parts. Thorton probably built his TX-RX around 1934 judging by the circuits and the parts used.

Don Thorton became an SK around 1940 and his son, Doug, was too young to remember his father using this TX-RX. Doug himself tried it out when he was in high school. The receiver worked fine and a friend listening on another receiver in town "thought" he copied the signal from the transmitter. Doug didn't have a license, so he didn't perform more than just the one test. Since then, the TX-RX has not been powered-up. Doug Thorton donated his father's homebrew TX-RX to the WHRM in October, 2010. Stay tuned for updates on this unit's functionability as we'll attempt to have it running soon. 


1935 HRO sn: D-65 (First Production Run) Rack Mount Receiver

National Company, Inc.  -  HRO, HRO Senior, HRO Junior - (1935 up to 1941)

National announced the HRO receiver in October 1934 and began production in January 1935 with the first receiver deliveries happening about March 1935. James Millen (at National) headed the mechanical design team and Herbert Hoover Jr. (on the West Coast) was in charge of the electrical design team. Millen and Hoover believed the best receiver performance was obtained using plug-in coils thus eliminating the losses found in most bandswitch circuits of the day. The HRO design also used a separate power supply in order to keep heat and hum out of the receiver. The HRO also used only the necessary number of tubes and all stages are run at maximum efficiency which lowered thermal tube noise and increased the signal to noise ratio. Many hams regard the HRO as the best of the pre-WWII ham receiver designs because of its great sensitivity with low internal noise along with its tremendous bandspread capabilities available on 80M, 40M 20M and 10M. It was an expensive receiver selling for about $200 with power supply and four coils in 1936. The HRO used 10 tubes (nine in the receiver and one in the PS) and featured double pre-selection on all of the plug-in coil sets. Plug-in coils for several frequency ranges were available and either general coverage or amateur bandspread were selectable on the amateur coil sets (A, B, C and D sets) by relocating  four "jumper screws" on top of the coil assembly.

The micrometer dial was based on a Sperry Gyroscope design (National's version was successfully patented) and the National version was very smooth in its operation. The PW-D (National's term for the micrometer dial) had a scaled range of 0-500 that gave the user the equivalent of a linear dial twelve feet long. The precision nature of the PW-D readout allowed for extremely accurate reset capabilities. The PW-D numerical readout was correlated to frequency graphs that were mounted on the front of each plug-in coil set allowing the user to determine the receiver's tuned frequency. For hams, the dial readout vs. frequency graph allowed the operator to figure out where he was tuned and was probably as accurate as most direct readout dials of the day. Of course, most hams then were using crystal controlled transmitters and knew their operating frequency anyway.

The HRO was one of the first receivers produced to feature double pre-selection, that is two TRF amplifiers, which reduced images to a minimum. Many hams were using earlier-type receivers with a separate after-market pre-selection to achieve what the HRO was already equipped with. The band spread feature was based on what National had been offering with the FB-7 and AGS receivers. The HRO increased the band spread to the point where each of the 80M, 40M, 20M and 10M bands were covered in 400 divisions of the PW-D. This was equivalent to a linear dial that was nine and a half feet long.

                                 photo right:
1936 HRO Senior sn: N-130 (10th production run) Table Top Receiver

There were several minor changes incorporated into the HRO from its 1935 introduction up to WWII. The HRO shown in the first photo is from the first production run and shows some of the earliest features of the initial run HRO receivers, that is, coil assemblies with white background graphs with black nomenclature, no pilot lamp, a nickel plated micrometer dial, black chassis, round IF cans, a "NC" on the dial pointer and a non-illuminated S-meter with a pearl-button push switch. The HRO Senior shown in the next photo is serial number N-130, built in June 1936, showing many of the changes that had been incorporated by the 10th production run. The last photo shows how the HRO Senior looked by 1940.

In 1936, the HRO Junior (photo to the left) was introduced as a reduced price version that eliminated the S-meter, the Crystal Filter and the bandspread coil feature (also, only one coil was included in the discount purchase price of $99.) With the introduction of the HRO Junior, the standard HRO became known as the "Senior." Also in 1936, the nickel plated tuning dial was changed to a black* painted lacquer version, chassis paint went from black to gray and the IF transformer shields were changed from round cans to square cans. In 1937, the S-meter became an illuminated unit and the following year the identification tag was added to the upper right corner of the panel.


photo left: 1936 HRO Junior sn: P-116 with original JD coil set installed - from the 11th production run

Initially, tubes used were 2.5v filaments if the AC power pack was used or 6.3v if battery operation was necessary but later either 2.5vac or 6.3vac tubes were optional. By the late thirties, only 6.3vac tubes were used. Millen believed that a lower noise figure was achieved using the 2.5vac tubes but later recanted this opinion as the 6.3vac tube quality improved. From the start, a rack mount version was also offered - it featured a crackle-finish, aluminum front panel (as D-65 shown in the first photo.)

The HRO shown in the last photo to the right is a 1940 HRO Senior (SN 463-K) with plug-in crystal. This version is how the HRO looked from 1938 up to about 1941. From this point and into the middle of WWII, the HRO doesn't change except that some late models will be found with a National "bar knob" for the Selectivity control rather than the round point knob.

For details on the WWII HRO versions go to "WWII Communications Equipment." For details on the post-WWII HRO receivers go to "Post-WWII Ham Gear." Navigation links are in the Index at the bottom of this page.

*The paint color on the PW-D varies from dark gunmetal gray to dark bronze. All dials appear black under normal room lighting and only show their true shades under intense light (like a photo flash.)

photo above: 1940 HRO Senior sn: 463-K

  For the ultimate in detailed information on all tube-type National HRO Series of receivers, including Production History, Serial Number Assignments, Performance and Restoration, click on
"National Co.,Inc. - HRO Communications Receivers - 'The Cream of the Crop"  in the index at the bottom of this webpage.



W6HLJ Xmtr with National FBX receiver

W6HLJ - 1935 Homebrew XMTR

Alvin Norberg, ex-W6HLJ, began building this professional looking transmitter in 1934 upon graduating from Manteca High School. He worked as a laborer for Spreckles Sugar Company to earn the money to buy the parts needed. A few years later he was graduating from UC Berkeley as a BSEE (1939.)

The transmitter construction is entirely made out of wood and masonite. Each section of the transmitter is built onto a wooden base (with the masonite front panel attached.) Each section slides into place on guides. The cabinet is made out of 1"x12" pine painted black. Al tried to duplicate the look of a Bell Labs rack out of wood. Symmetrical layout with matching meters, function ID tags, 4" diameter knobs and purf-metal viewing ports added to the professional appearance. Al baked the wrinkle finish paint inside his mother's wood stove oven. Al said,

"When the transmitter was keyed all of the meter needles swung together and the mercury rectifier tubes flashed their blue light. When the key was held closed the plate of the final amplifier Heintz & Kauffman HK-354 would glow red! WOW!"

photo above: 2 photos - The W6HLJ Xmtr as it looked in 1935. Note that it is not yet painted.
Inside the transmitter the circuit is a crystal-controlled 6L6G oscillator that can be front panel switched to three different plug-in crystals. The buffer stage uses a Western Electric 211-D and the final amplifier is a Heintz & Kauffman "Gammatron" HK-354. The transmitter is CW only and originally ran 1 KW input power or about 700 watts output power. The PA plate condenser is homemade and was built by a machinist (the father of a friend) who made a gift of the precision made condenser. The plate transformer was a salvaged "peg-pole" transformer that was used to provide around 4000vdc on the plate of the HK-354. Unfortunately later in the transmitter's life, the original plate transformer was removed to lighten the total weight for easier moving. I have found a very nice 3K-0-3K plate transformer that looks similar to the original transformer and can handle 500mA. This level of plate voltage should easily provide about 750 watts input power and about 500 watts output. Whether we will be able to actually have a 2X CW QSO will depend on the level of RFI we encounter considering that the transmitter has absolutely no shielding whatsoever. Stay tuned for further updates as this restoration project continues.

Update for July 2013: Al Norberg, at the age of 97, is still a registered EE with the state of California. He recently (June 2013) donated his Speed-X bug that can be seen in the B&W photos and also the National Type-N dial that can be seen on his homebrew three tube receiver that is in the B&W photo. Unfortunately, the receiver was "parted out" years ago but building a duplicate is a possibility. The transmitter has been moved and is now at our new QTH in Dayton, Nevada. The top half of the transmitter is restored but the power supply section is still awaiting rebuilding before a test transmission could be made. Go to our webpage "Telegraph Keys" to see a close-up photo of the W6HLJ Speed-X. Navigation link in the index at the bottom of this page. 


Breting Radio Mfg.  -  Breting 12

Paul Breting started selling communications receivers in 1935. Breting built his receivers at Gilfillan Bros., Inc. in Los Angeles, California. Ray Gudie, famous for the Patterson PR-10, was Breting's chief engineer. Gudie came over to Breting after a wage dispute with Emmitt Patterson. Gudie felt the success of the Patterson PR-10 should have warranted him a salary increase - Patterson disagreed in a manner that caused Gudie to resign and go to work for Paul Breting. The Breting 12 was Gudie's first major design for Breting and it was introduced in 1935 for just under $100. The circuit was a 12 tube superhet that featured a second RF Pre-amp above 7.0Mc, band-in-use dial scaling, xtal filter, two meters (R-meter & Volume meter) and P/P 42s - all on a chrome chassis. The ham owner could also use the receiver's audio section as a speech amp to drive a separate transmitter modulator. The BFO adjustment is a knob located under the bottom of the cabinet. The dial had "oak leaves & acorns" decor on the early models while later dials had vertical "rays" flanking the "12" on the dial. Breting, along with all other West Coast radio builders, didn't have the necessary RCA Superhet license so his receivers were assembled at the exclusive "RCA licensed" Gilfillan plant in Los Angeles, California*.  The serial number on this Breting 12 is "21685." The published Breting schematics are fraught with errors and rarely agree with the receivers produced.
UPDATE:  March 2018 - I now have another Breting 12 receiver that's the later version of production with the "vertical rays" flanking the "12" on the dial (serial number "28952.") I purchased it from a local "antique dealer" that had found it in a derelict, run-down barn in Carson Valley, Nevada. However, since this new "12" was a "barn find," the exterior is in absolutely terrible condition due to decades of rodent activity (generally, using the top of the cabinet as a latrine.) Luckily, the vermin were unable to gain access inside the cabinet and the chassis top and bottom look good. The chrome chassis appears to be in much better condition than the early version receiver shown above. The cabinet and front panel, however, will require complete decontamination, stripping, metal filling and probably a number of other treatments to get it to the point where a new black wrinkle finish paint job can be applied. More info when the project gets started.

Jan 15, 2019 - Began disassembly and cleaning of the Breting 12 (sn: 28952.) Chrome is pretty good but not perfect. Cleaned up to look very good. Dials and band in use mechanism needed to be disassembled to clean and lubricate. Tuning condenser needed to be cleaned and lubed. The dial drive mechanism is a "pinch wheel" that drives the logging dial. The logging dial shaft gear-drives the main tuning split-gear that is mounted to the tuning condenser shaft. Nothing fancy, so with cleaning the dial-condenser drive works just fine. The band-in-use scaling is accomplished by a gear mounted to the band switch shaft driving the dial scale assembly rack-gear vertically. Again, nothing fancy, so with cleaning and adjusting, the band-in-use scaling works fine. 

Photo to the right shows the cleaned chassis of SN: 28952. Note the difference in the dial mask decoration in that the later Breting 12s have vertical "rays" and diamonds while the earlier dial mask has the "acorns and oak leaves" as seen in the SN: 21685.


Patterson Radio Co.  -  PR-16C

Patterson introduced their 16 tube receiver in 1935. After engineer Ray Gudie left Patterson over a wage dispute, Emmitt Patterson tried engineering the new PR-12 Communication Receiver but soon discovered he was completely out of his element. Though the PR-12 Communication Receiver appeared in a few advertisements in late 1934 it was never in production. A few prototype PR-12 Communication Receivers have turned up but they appear crude and not like a true production receiver. Also, Patterson did produce a 12 tube All Wave receiver that was generally housed in a floor model wooden console cabinet and this chassis is sometimes erroneously referred to as the PR-12. The PR-12 Communications Receiver was a different design that probably never went into regular production.

Patterson hired Karl Pierson to complete the PR-12 Communication Receiver but Pierson took one look at it and scraped the whole project. Karl Pierson then designed the PR-16 in just a few weeks as the "new" Patterson receiver. The PR-16 featured parallel RF amplifier tubes (2-6D6s) which, in theory, increased the gain and reduced thermal noise. It also allowed the receiver to be advertised as having two RF amplifiers, even though there was only one set of RF coils per band and the receiver is essentially a single preselection front-end. The incredible audio section has three stages of Push-Pull audio using a 6A6 dual triode, two 76 triodes and two 42 output tubes supplying 18 watts of low distortion audio power (some early versions had P-P 6A3 tubes.) The BFO adjustment is a "swing-arm" lever accessed under the cabinet lid. Chrome chassis, band-in-use dial masking, illuminated R-meter, crystal filter, two-speed tuning - all for the low price of $101.70, (1936 price.)

Even though the parallel RF amplifiers are unconventional and no other manufacturers ever tried to market the configuration - the PR-16C is a good performer with good sensitivity, nice mechanical bandspread and powerhouse audio. Built at the Gilfillan plant.*  This PR-16C belonged to W6BBK, who bought it new in 1936, using part of his WWI veterans bonus to fund the purchase.


Doerle Globe Circler

In the 1930s, Walter C. Doerle of Oakland, California, came up with several types of regenerative detector receivers for the "homebrewer." Hugo Gernsback published a book that was titled "Four Doerle Receivers You Can Build" which was apparently very popular. In fact, the Doerle-circuit receivers became so popular with "homebrewers" that some builders started "Doerle Receiver" clubs. The receivers generally were a regenerative detector in combination with a single stage of audio amplification. Usually, type-30 tubes were specified but 201A tubes were also popular (although they didn't have the gain that type-30 tubes did.) To keep costs down, the Doerle receivers were always battery-operated. Audio reproduction was for a Hi-Z headset.

Like any homebrew or kit, Doerle receivers are unpredictable as performers. Most homebrew builders weren't radio engineers or technicians. They weren't experienced assemblers like those that worked in radio factories so many homebrewers lacked the basics in good soldering ability. Most homebrew builders during the Depression didn't have any test equipment. Careful winding of the coils required experience and well-made coils helped to provide the best performance from the simple Doerle circuit. Since many homebrewers lacked basic electronic skills, few adhered to layouts or instructions so most of the receiver wiring will have a variety of problems from lead dress and component placement to fundamental wiring errors.

As expected, the Doerle Globe Circler shown above doesn't work all that well. It was mechanically well-built using several pieces of Atwater-Kent radio parts salvaged from mid-twenties sets. The builder did have a lot of confidence in his ability since much of the construction was assembled with glue and nails preventing any disassembly to check wiring and quality of workmanship. The use of an iron vane meter to monitor filament voltage was a very nice touch. At one time there may have been a second coil for other frequency coverage but the one coil that is present allows tuning from approximately 3.0mc up to about 6.0mc. Since the regenerative detector has very little isolation from antenna effects, this Doerle Globe Circler prefers a fairly short antenna - fifty feet seems best. Longer antennae add so much inductance to the regenerative circuit there isn't enough plate tuning to effect regeneration. The problem may be due to the coil construction which is very poor and the antenna effect maybe due to over-coupling in the way the coil is wound. However, the Doerle Globe Circler does receive 5.0mc WWV and a few SWBC stations. A few SSB 75M hams have also been received. This Doerle Globe Circler would certainly benefit with a complete redesign and rebuild but then it wouldn't be original and serve as an example of the typical 1930s homebrew regen-set.

Many radio enthusiasts still build Doerle regenerative receivers. Some builders prefer to use mostly vintage parts while others, trying to get "the most" out of the circuit, use modern equivalents. There's ample info on the circuits and performance reviews on the Internet.


1936 TOBE "Special" Model H

Tobe Deutschmann Corporation

TOBE Amateur Communication Receiver Model H,  TOBE "Special" Model H, Wright-DeCoster/TOBE Loudspeaker

Radio kits were one way an enthusiast could purchase a fairly advanced receiver and only pay a fraction of the cost of a commercially-built receiver. Kit-building was very popular during the twenties when radio broadcasting was starting and the cost of a factory-built radio averaged over $100 (and that didn't include the accessories like tubes, loudspeaker or batteries.) By the 1930s, kit-building had lost some of its appeal since many broadcast radios were inexpensive by then. Amateur radio had been the domain of the "homebrewer" - someone who built their own equipment. By the mid-1930s, amateurs had accepted that the superheterodyne receiver was a superior performer on shortwave and most had decided that these modern receivers were just too complex for the homebrewer to tackle. Factory-built receivers were used in just about all ham shacks while the transmitters used were almost all homebrew.

Glenn H Browning had been thinking about easing the complexity of homebuilt receivers around 1934. Just how to construct a kit-type superheterodyne that eliminated some of the more difficult tasks, especially those tasks that required special test equipment, was Browning's goal. He designed a receiver "front end" that used a tuned RF amplifier and a Converter stage with all of the coils necessary for four bands tuning from the AM BC band up to 22mc. Tobe Deutschmann Corporation offered the Browning Tuner (by then called the Tobe Super Tuner) as the foundation of a kit called the "Browning 35" (since it was going to sell in 1935) All of the components including the pre-built and pre-aligned "Tobe Super Tuner" were in the kit, even a loud speaker, for the very reasonable price of $46.

The Browning 35 was a general coverage receiver for shortwave listeners, hams and enthusiasts. What the hams wanted was an inexpensive "ham bands only" receiver. Tobe Deutchmann Corporation offered the "Tobe Amateur Communication Receiver - Model H" that was essentially the Browning 35 but only tuning 160M, 80M, 40M and 20M amateur bands in a band spread type of coverage. The Model H used the "Tobe 35H Tuner" that was a version of the Tobe Super Tuner that had a special tuning condenser for band spread coverage of 160M, 80M, 40M and 20M. There was actually some frequency coverage slightly above and below each ham band to allow for reception of a few short wave broadcasters, foreign hams and other stations outside the US ham bands. Since the front-end was pre-aligned, the builder had only to assemble the receiver (Tobe Deutschmann's instructions say "a few enjoyable hours" were required for assembly) and then do a minor "touch up" alignment to the triple-tuned IF and to the front-end. Instructions consisted of five large drawings showing the proper placement of components, a large schematic, written instructions and a booklet. There are a couple of pages that warn assemblers not to use acid or paste flux for soldering or "problems will result." Like all radio kits of the thirties, TOBE assumed that the builder had some experience so "step-by-step" instructions are not provided. The instructions are general information and only convey special information where needed. The builder was supposed to adhere to the drawings and the schematic for proper assembly. The large drawings are numbered 1 thru 5 so the builder would start with drawing #1 performing those tasks and then moving on the drawing #2, so on, until drawing #5 was completed and that had the receiver ready to test. Any detailed mechanical assembly instructions were thought to be unnecessary and that information is only shown in the drawings.

The Tobe Model H was available from 1935 up through 1936. The 1935 versions use seven glass tubes. The power transformer had both 6.3vac and 2.5vac windings so the builder could choose either 2.5vac tubes - (2) 58, (1) 2A7, (1) 2A6, (1) 56, (1) 2A5, (1) 80. Or, using 6.3vac tubes the line-up was (2) 6D6, (1) 6A7, (1) 75, (1) 76, (1) 42, (1) 80. There isn't a bezel surrounding the dial on the 1935 models. Instead, a small oval metal plate with logging scale and band select numbers is used. Dials on early versions will have the "TOBE" logo and receiver model information printed below the band scales. The 1936 models will have a large silver metal bezel surrounding the dial, integrated to include the logging scale and band select nomenclature. The "TOBE" logo and receiver model are printed on the bezel. The dial just has the band scales. In 1936, either the seven glass tubes circuit could be purchased or the eight metal tubes circuit could be selected. Also in 1936, a spring-loaded ball latch was added to the cabinet lid.

When completed, the Tobe Model H had one RF amplifier, a Converter stage, a single IF amplifier, a single detector, BFO, a first AF stage, an AF output and a power supply rectifier. After alignment the sensitivity was rated a 1uv and with the very selective RF tuning, along with the tertiary link-coupled IF transformers, the bandwidth was fairly narrow. The later 1936 versions of the Model H were also available with air-tuned trimmers for the oscillator circuit for better stability and accuracy requiring the Type 2 LO assembly be added to the 35H tuner which added about $10 to the selling price of the kit for a total of $56 for the metal tube version with air trimmers (called the "TOBE Special.") Tobe Deutschmann mentioned that a Crystal Filter IF transformer that was going to be available but it was never shown in their advertising as an option. Audio output was rated at 3 watts (with either a 2A5, a 42 or a 6F6 output tube) driving an electrodynamic speaker with a field coil resistance of 1750 ohms. 

photo above: The 1935 TOBE Amateur Communication Receiver Model H

Although a speaker was included, it didn't have an enclosure. Complete Wright-DeCoster speakers with enclosures could be purchased to go with the Tobe receivers (see the Wright-DeCoster speaker shown below.) A front panel "standby" switch was provided for the Model H. The tuning dial is removable thru a slot in the top of the receiver cabinet to allow the user to install a customized tuning dial that provided markers to indicate ham "schedules" by call and by day of the week. Besides the main dial logging scale there is another logging scale that surrounds the tuning knob. Twenty divisions on the tuning knob scale equals ten divisions on the main dial logging scale. The dial illumination is provided by a dial lamp that is mounted to the tuning condenser shaft. This provides a "tracking" illumination that follows the dial pointer - very cool.

The TOBE "Special" Model H shown in the top photo is a 1936 version "TOBE Special" using all metal octal tubes and utilizing the air-tuned trimmers. Tube line up is 1-6K7 RF Amp, 1-6A8 Converter, 1-6K7 IF Amp, 1-6H6 Det/AVC, 1-6C5 BFO, 1- 6F5 1st AF, 1-6F6 AF Output, 1-5Z4 Rectifier. Along with the receiver I was also able to obtain all of the original instructions including all five of the large drawings, schematic, written instructions and the Browning 35 booklet. Also, the alignment dial and the main tuning dial. The "Special" photo shows the standard tuning dial inserted.

1935 TOBE Amateur Communication Receiver Model H - This is the early version of the Model H using seven glass tubes. Note that the dial doesn't have the large bezel that was used on the 1936 models. This particular Model H is heavily modified. Not totally unexpected from "kit built" equipment. After all, the builder felt that he was totally familiar with the circuit and therefore felt qualified to modify it's design. In some cases, minor modifications made sense and sometimes improved the usability of a piece of equipment. Other times the mods were to repair the receiver when the correct parts weren't available (or affordable) and the parts used came from the "junk box."  Is this Model H restorable to original? The biggest problem is that the two TOBE IF transformers with the special tertiary link have been replaced with standard Meissner IF transformers. This changes the selectivity that the original transformers provided. Another mod will require the removal of a 0A2 regulator that will require a hole filler plug. Also, somewhere in the history of this receiver the original 42 audio output tube was replaced with an octal 6F6 requiring finding a fiber board six-pin tube socket with "42" stamped on it. Other "originality" problems are simply due to years and years of repairs and random component changing. If I can locate the correct "T-1" and "T-2" TOBE IF transformers, then the rest of the receiver will be fairly easy to restore to original. Capacitors will have to be built and since I have the correct TOBE labels from the "Special" to copy that should be an easy task. First step is to find the two proper TOBE IF transformers. The restoration procedure will be similar to what I had to do to the TOBE "Special" when performing its restoration (described somewhat in the next section.)     

Observations on Restoring Radio Kits:  Even though the TOBE "Special" Model H kit provided the builder with excellent, large drawings for all aspects of construction along with detailed (for the thirties) written instructions, there is the possibility that any Model H kit is likely to be fraught with problems that have the root cause being the lack of experience and minimal technical expertise of the builder. Most kit builders were not professional electronic assemblers. Most kit builders didn't have soldering skills that were even close to the professional assemblers found in "radio factories." Expect to find poor soldering joints, minor wiring problems, lead dress problems,...on and on. Most kit builders were not professional electronics technicians or engineers. Many didn't own any type of test equipment. You may find that you have to thoroughly go over all of the circuit inspecting for bad grounds due to mechanical assembly problems, poor solder joints, lead dress problems and wiring or component errors. For example, the 1936 "Special" Model H shown in the top photo was basically complete and original having only been recapped in the past. It did function but exhibited several problems, from a fairly high hum level to an AC modulated CW note. LO tracking was poor and couldn't be aligned. The articulated dial lamp assembly was missing. A thorough inspection found so many lead dress, component location and soldering problems that the only solution was to completely "strip out" the wiring and components and start over - this time following the recommended layout using professional wiring and soldering techniques. All of the original components were rebuilt or reused so the "newly built" Model H appears just like it had been assembled following the instructions back in 1936. When finished, the performance was significantly better and also pretty much as described in the booklet. Unfortunately, the Tobe alignment instructions provided are useless since they assume you don't have any test equipment. I aligned the Model H as if it were a standard ham band superhet receiver with a 456kc IF and ended up with a receiver that has very good sensitivity, fair selectivity, vague dial information, very nice audio in the AM mode and average stability for the period. Back in 1936, for the expenditure of around $60 and a few nights of assembly and testing, the talented, experienced and thrifty ham would have ended up with a pretty good receiver at about half the price of a factory assembled receiver. 

Wright-DeCoster Loudspeaker for TOBE Model H Receivers

When the TOBE Model H Amateur Communication Receiver kit was purchased a loudspeaker without enclosure was included. For an extra five dollars, an optional loudspeaker was also available for use with the various Tobe Deutschmann receivers, the Browning 35, the TOBE "Special" Model H and the standard TOBE Model H. The loudspeaker was an eight inch Wright-DeCoster electrodynamic speaker housed in a metal cabinet that was painted black wrinkle finish. The field coil DC R was 1750 ohms and the proper audio output transformer was mounted on the speaker frame. A four conductor cable with four pin plug connected the loudspeaker to the receiver.

The photo to the left shows a Wright-DeCoster/TOBE loudspeaker that uses an eight inch W-D loudspeaker. The grille cloth was originally silver and black but this example of original grille cloth has faded and discolored to now appear brownish tweed in pattern and color. The "sunburst" grille featured a small metal badge in the center that is missing from this example. The badge probably had the "W-D" script-logo on it.


 The Hallicrafters, Inc.  -  SX-9 

Bill Halligan bought Silver-Marshall Mfg. to start The Hallicrafters, Inc. and began offering receivers in 1933 with the first receiver designs using TRF circuits. All of the early Hallicrafters receivers were built by contractor radio companies, like Howard Radio Company and other contractors, since S-M didn't have a  manufacturing plant or the RCA Superhet license. Halligan formed a partnership with Case Electric to use their license and plant in early 1936 and shortly thereafter purchased Echophone to acquire their RCA superhet license and manufacturing plant. The SX-9 was offered in late 1935 through early 1936 and featured a built-in speaker, nine metal-type tubes and Aladdin iron-core IF transformers in a superheterodyne circuit with bandspread. All SX-9 receivers were built by contractors and the serial number tag will have a manufacturer code number for identification. Though the SX-9 was a significant improvement over earlier TRF models and performance is quite good, it still retained a somewhat crude "amateur" appearance. Like most Hallicrafters receivers, the SX-9 was designed to be built from "purchased parts" supplied by various component companies. This design and manufacturing method allowed Hallicrafters to offer great performing receivers at reasonable prices.


The Hallicrafters, Inc.  -  Sky Buddy Series - 5 -T "SKY-BUDDY", S-19 & S-19R "Sky BUDDY"

Hallicrafters believed there should be a market for an inexpensive shortwave receiver that would perform well enough to inspire young enthusiasts to choose "RADIO" as a hobby or as a career. First, the youngster would become an SWL (Short Wave Listener,) then go on to become a ham and finally would make RADIO a career. The idea certainly appealed to the parents of technically talented kids and it was those parents that were the target market for "entry level receivers." Hallicrafters' goal was to be able to produce the receiver at a cost low enough for the Depression-era parents of 1935 to afford the set for one of their "radio-minded" youngsters. At $29, the 5-T Sky Buddy was certainly low priced (about $250 in 2013 dollars) and with 5 tubes the performance was adequate to inspire hoards of young users into becoming hams. Many hams remember that their first listening experience to shortwave reception was on an "entry level receiver." (Of course, today most older hams remember the Sky Buddy's post-WWII successor, the S-38, as providing their first SW reception. As a kid, my first successful shortwave listening was on a second-hand S-38B.)
To ensure that the purchasers knew who the intended users of the 5-T Sky Buddy were supposed to be, the first few production runs included a picture of a "young ham sending with a bug" on the dial. A close-up of the dial is shown in the photo to the left. The 5-T was successful and popular. So popular, in fact, that many adults were buying the receiver for their own use. In a short time, Hallicrafters removed the "boy dial" and just used a plain dial with "SKY BUDDY" written across the center. Maybe this was to make the receiver look less like a kid's toy and more like a serious ham receiver. Note in the close-up of the "boy dial" that the boy is depicted using a semi-automatic telegraph key (bug) and is listening using "phones" just like a "pro." Of course, the vest and tie help for that future job interview to get into professional RADIO!

The "no boy" model 5-T was produced up to around 1938. By then the airplane dial was becoming passť and Hallicrafters had been using an external metal dial on their larger receivers so the Sky Buddy was revamped with a new dial and a few tube changes. The model number changed to S-19 Sky Buddy. Later, in 1939, other improvements warranted another model number change to S-19R. The major features of the S-19R were the added band spread dial and another tube to the circuit bringing the total to six. The price was also increased to $39. The early S-19R receivers use toggle switches but the very late versions (just before WWII) replaced the toggle switches with slide switches.

After WWII, the Sky Buddy returned,... well, the concept of an "entry level receiver" returned. The new version was designated the S-38. The S-38 eliminated the AC power transformer used in the pre-war Sky Buddy and went with an AC-DC circuit. Six tubes were used in the first S-38s but soon that was changed to five tubes when the BFO became a gimmick in the IF to cause oscillation and the Noise Limiter circuit was dropped altogether. Still, many hams remember the S-38 as their first exposure to shortwave reception and the little receiver was an amazing performer given its obvious limitations. The S-38 went through a series of upgrades running from the S-38, S-38A, B, C, D and E. Also, a faux mahogany cabinet S-38EM along with a blonde finish cabinet S-38EB. 

Ultimately, the Sky Buddy name returned with the S-119 receiver (also available as a kit, S-199K.) Although the idea and goals of interesting youths in RADIO was still somewhat popular, times had changed with television encroaching into the domain of RADIO with the ham often viewed as a TVI nuisance to the neighborhood rather than the valuable emergency asset he could be. The S-119 Sky Buddy II never gained the popularity or memories of the original Sky Buddy or the S-38 Series. 

Nostalgia certainly drives the collector market for Sky Buddy series. The performance of these receivers is very limited with rampant images since no RF amplifier was used in any of the series. They are easy to restore and when operational hopefully will bring back memories of youthful excitement when receiving signals from foreign countries.

Go to our webpage "Post WWII Ham Gear" for more info on the Hallicrafters S-38 series. Navigation link below in the Index.

photo right: 1941 Sky BUDDY S-19R. Note that this version has Band Spread. On all of the pre-WWII versions of the Sky Buddy, the speaker grill is flocked with a mohair felt that is usually dark brown or olive-brown color. On nearly all examples found today the flocked felt has fallen off or has been rubbed off so that only the wire screen part of the grille is left. 


Radio Manufacturing Engineers, Inc.  -  RME-69, DB-20 Preselector

The RME-69 was announced in November 1935. Using nine tubes, a stout chassis and a tight, compact layout, the RME-69 provided the user a receiver with lots of sensitivity along with great performance features and a tuning and bandspread dial system that was "velvet smooth" - even though the dial nomenclature was miniscule. At least the dials were significantly larger than the RME-69's predecessor, the RME-9D, with its small round airplane dials that were almost impossible to read. Also, the tubes were now 6 volt heater types, e.g. 6D6, 6C6, 6B7 and 42 with an 80 rectifier. The "Compensator" control (located between the two main tuning knobs) allows the operator to keep the RF and Mixer stages "peaked" for any frequency tuned. "Stand-by" is actuated by pulling the Audio Gain control knob. A terminal on the rear chassis allows the station transmitter's AM signal to be monitored through the receiver. The Carrier Level meter is calibrated in both "R" units and in db (with 48db equal to R-9.) The standard RME-69 covered .55 to 33MC and sold initially for $135 - the price was raised to $151 in 1937. Throughout production various improvements were incorporated into the design. The RME-69A was an AC or Battery operated version and the RME-69B was battery operation only. Late in production changes were made to the mounting of the BFO switch and headphone jack, the mounting of the two dial lamps and the Crystal Filter design. Another late offering was the Lamb Noise Silencer, designated as the LS-1 option (there was also an LS-2 variation for battery operation.) The LS-1 added two extra tubes to the circuit and changed the IF amplifier tubes to metal octal types.

A popular RME accessory was the DB-20 Pre-selector, introduced in October 1936. It provided the user with two tuned RF stages ahead of the RME-69 with an advertised gain of 20 to 25 db along with reduction of images. When the RME-69 was used with a DB-20, three tuned RF amplifiers were in operation - sensitivity was incredible and images were no longer an issue. A VHF Converter was also available. RME also offered the DB-20 and the RME-69 installed into one very long cabinet. The matching speaker is mounted in an unusual trapezoid shaped cabinet that allowed for a bench corner to be used for the speaker location and then rectangular equipment cabinets could be butted against each side of the speaker cabinet. Early versions of this speaker cabinet used Rola speakers while late versions used Jensen speakers. In 1939, the RME-70 was introduced and the RME-69 was slowly phased out of production. About 6500 RME-69s were built from 1935 up to about 1940. Shown in the photo above is our 1937 RME-69 SN 1931 with its matching speaker and matching DB-20 Pre-selector. Serial numbers on early receivers are numerical and are probably actual sequential numbers for the quantity of receivers built. Around 1938-39, the serial numbering system was changed to a letter-number combination that probably represents sequentially numbered receivers within specific production runs with the production run identified by the letter used in the serial number.

If you are aligning an RME-69 be aware that it has a decidedly different front-end with no trimmers to compensate for variations in the coil windings of the RF or Mixer sections. This was because the coils were all pre-tuned before assembly and all coils should be identical from receiver to receiver. Whether they have aged the same over the past 70 years is an unknown but most seem to have weathered time quite well. Since the alignment requires some special information, it is lucky that the quirky alignment procedure is in Rider's VOL. X. When aligning the RME-69, it will be noted that the adjustments for the LO are compression trimmer capacitors which are notorious for not "holding adjustment." RME, more than any other communications receiver company, believed that the "ham owners" of their receivers were "tinkerers" - the type that was always adjusting this or aligning that. The fact that the LO might need adjustment every few months didn't bother that sort of owner and apparently didn't bother RME either.

The RME-69 by itself is a typical late-thirties performer, however when rebuilt and aligned, the RME-69 used with the DB-20 preselector is an almost unbeatable vintage receiver. It will be noted that some of the components used in construction are somewhat on "the cheap side." Also, it appears that several parts are just AM BC radio parts that were purchased to construct the receiver. Although Hallicrafters made their reputation on using purchased parts to construct their receivers, RME didn't have that sort of reputation. RME's style of advertising promoted the "engineering" side of design rather than the source or quality of the components used. Still, the RME receivers do perform quite well when rebuilt and aligned correctly.

W7UIZ's RME-69LS-1/DB-20 Rack Mount

In 1940, Gordon Harris became the youngest licensed ham in the state of Nevada at the age of 12. His father bought him this RME-69 with the LS-1 Lamb Noise Silencer along with the DB-20 preselector and matching speaker - all rack mounted in an RME table-top rack assembly. Quite a receiver for a young ham but Gordon was a genuine enthusiast. He also became Nevada's youngest holder of a FCC First Class Radiotelephone License at the age of 16. He was hired by radio station KOH in 1944, when station manager Bob Stoddard couldn't find any FCC-licensed engineers available due to the demands of WWII. Gordon's "read-the-copy" test was a dismal failure. Those of us who knew Gordon's rapid-fire, whispery voice knew he'd never be the announcer on KOH.  Instead, he was put to work at KOH for his technical abilities, working after school and on weekends. After WWII, Nevada went from the sixth call district to the seventh and Gordon's call became W7UIZ, which he kept until he became an SK in 2012. It's very rare for a ham to have kept his original receiver, especially over a 72 year period of time. I was given Gordon's old receiver by his son in 2015.

The RME-69LS-1 is a very late version of the receiver with the BFO switch being a toggle switch located in the lower left corner of the panel. The Crystal Filter is the late version without the "series-parallel" function. In the lower right corner is the Noise Silencer control. The Lamb Noise Silencer was only used in a few receivers (with the Hallicrafters SX-28 being the best known.) The Lamb NS actually is a tuned-IF noise blanker that works quite well on both voice or cw. It required two extra tubes and one IF tuned transformer. The Lamb NS is built onto a small chassis (which also has the two IF amplifier tubes mounted on it.) The LS-1 version of the RME-69 uses a 6L7 and a 6K7 in place of the older two 6D6 IF amplifier tubes. The Noise Silencer uses a 6J7 and a 6H6.

The DB-20 is a two-stage TRF preselector that was a very popular accessory for the RME-69. This version is rack mounted with a full size 19" front panel. The speaker panel uses the standard 8" Jensen PM speaker with matching transformer. All of the panels are .190" aluminum finished in gray wrinkle paint with engraved nomenclature. Normally, RME didn't provide any panel control information believing that the ham should know his receiver and know the functions of the controls without any nomenclature required. This rack mount RME-69 is somewhat of a departure from that belief and all control functions are well-identified with engraved nomenclature.

Radio Manufacturing Engineers, Inc. was very successful during the 1930s and was certainly a true competitor to the "Big Three" (National, Hammarlund and Hallicrafters.) However, RME didn't evolve from their 1930s design concept and, after WWII, the company began to stagnate. With new ownership under ElectroVoice in the early 1950s, a few newer models emerged. The most famous was the very modern RME-6900. ElectroVoice sold the RME name to G.C. Electronics in 1962. The RME name faded away shortly after.


1936  "Super-Pro" SP-10 from WMI

Hammarlund Mfg. Co., Inc. - "Super-Pro" - SP-10 Series, SP-100 Series

Hammarlund spared no expense to build the very best communication receivers available from the mid-thirties through most of the 1940s. Uncompromising quality made the Super-Pro the choice of professionals, both military and commercial, along with the few well-to-do hams who could afford the $400 list price (though most discount dealers offered the Super-Pro with Crystal Filter for about $250.) Designing began as early as 1933 (when it was referred to as the "Comet Super-Pro") but the official QST introduction wasn't until March 1936. Hammarlund had the Super Pro ready long before March 1936 however and was supplying the Super Pro receiver to the U.S. Army Signal Corps as the SPA receiver. The order number was 10932-NY-35 and is dated June 29, 1935. The SPA is identical to the Super-Pro that was introduced nine months later, indicating that as far as Hammarlund was concerned, the Super Pro was ready mid-1935.

The Super-Pro used several custom designed parts, including its variable-coupled air-tuned IF transformers, its silver-plated cam-operated bandswitch and its four-gang main tuning condenser and twelve-gang bandspread condenser. Using 16 tubes, the circuit featured double pre-selection on all bands with 25 individual laboratory tuned coils mounted on 20 Isolantite bases, frequency coverage from .54-20MC, amplified AVC, front panel adjustable BFO and 0.5% dial accuracy (incredible for the time.) The variable-coupled IF transformers allowed the user continuously adjustable IF bandwidth from 16KC down to 3KC. Separate RF Gain, IF Gain and Audio Gain controls were used and even a Tone Control was provided. A separate power supply was included in the purchase price (along with a speaker.) The power supply provided three levels of B+ voltage, -C bias voltage and tube heater voltage, all connected to the receiver via a five foot long, nine wire cable that had a special terminal strip type connector on each end. 

The first Super-Pro, commonly referred to as the Model SP-10, used all glass tubes with vented shields on the all but the audio tubes. The audio section including triode connected P-P 42s driven by another triode connected 42 with potted audio transformers with an 8 ohm Z output. Some SP-10 receivers had a 600 ohm Z audio output that added resistors to the audio line output to achieve a 600 ohm Z while utilizing the standard 8 ohm Z transformer. The first, second and third IF transformers were variable-coupled and cam/lever controlled from the front panel Selectivity control. Additionally, the Input and Output IF transformers for the Second Detector and the Output transformer for the amplified AVC were also variable-coupled but adjustable via knurled nuts on threaded shafts that protrude out the top of each transformer housing. The front panel was .190" thick aluminum finished black wrinkle then engraved so the nomenclature would appear bright silver (when it was clean.) The separate power supply was designed to utilize the field coil on the standard 8"speaker (a 12" deluxe speaker was available at $25 extra.) The speaker was just that - a speaker, no cabinet was supplied. The Tuning Meter was not illuminated and had an arbitrary 0 to 5 scale (but with 50 divisions!) Since it measured total IF amplifier plate current, stronger carriers would increase the AVC voltage, reducing the IF gain thus resulting in a lower reading on the meter scale. When tuning in AM stations, one would tune for the lowest reading on the meter. Signal reports were based on the difference between the "no signal" meter reading versus the "signal' meter reading to calculate "db over noise." Bandspread was only operational on the upper three frequency ranges and used a 0-100 logging scale. The crystal filter option was designated with an "X" suffix added to the model type. In mid-1936, an "S" version was offered that had coverage from 1.2 to 40MC with bandspread on all five tuning ranges (identified with an "S" suffix.) This model was advertised extensively in ham magazines of the day. The SP-10 designation is a later identification addition, when new, the receiver was just advertised as the "Super-Pro." The SP-10 was in production for only nine months but, if the SPA is included as a SP-10 receiver, the production lasted about a year and a half.

1937 "Super-Pro" SP-100X

The SP-100 series Super-Pro was introduced in January 1937. Changes included going to metal octal tubes in the RF front end and in the audio section - eight tubes in all were changed (2-6K7, 6L7, 6J7, 6C5, 3-6F6,) the other eight tubes remained large glass tubes, (3-6D6, 6C6, 2-6B7, 5Z3 and 80 - the 80 was a change from the 1-V tube used in the earlier supplies.) The separate RF and IF Gain controls of the SP-10 were combined into a single Sensitivity control on the SP-100. The "knurled nuts" adjustable-coupling Second Detector Input and Output IF transformers and the adjustable-coupling Amplified AVC Output transformer of the SP-10 were changed to fixed-coupling units on the SP-100. The front panel was still .190" thick aluminum, wrinkle finished then engraved and now reference scales were added to the BFO, Bandwidth, AF Gain and Sensitivity. The "unique" Tuning Meter remained unchanged but the audio transformers were changed to vertical mount, frame-types with 8 ohms Z audio output. Added to the rear chassis apron was a two input pin jack socket that provided a remote relay access to control the receiver B+ by paralleling the Stand By switch. Around the same time the size of the standard speaker was increased to 10 inches. The standard power supply still had field coil connections on all versions but chassis space was provided for the substitution of a filter choke to replace the speaker field coil which then allowed the use of a PM speaker. Although not mentioned in advertising, an "L" version was available that included longwave coverage 100-200KC and 200-400KC in place of the .54 to1.25MC and 1.25-2.5MC bands. The "L" model also featured a front panel "Phone" jack and a dual secondary winding on the audio output transformer. A special SP-100X was built for Swedish government use, the Markradiomottagare 5, or MRM-5. These receivers were standard SP-100X configuration except for the frequency coverage - 200KC to 400KC and .54MC to 10.0MC. The Swedish manuals are dated 1937.

Hammarlund always used "Series 100" in their advertising but model designations in their sales literature usually are SP-110 or SP-120 with 10 or 12 denoting the speaker size. Model designations also include suffixes that identify the tuning range and installation of a crystal filter - "no suffix" tunes .54 to 20MC, "S" tunes 1.2 to 40MC or "L" tunes 100-400KC and 2.5-20MC. The addition of  an "X" suffix denotes the installation of the crystal filter option. The serial number on all Super-Pro receivers is located on the rear apron of the chassis, stamped into the metal. Great sensitivity and fantastic audio with continuously variable selectivity make the pre-war Super-Pro receivers a natural for a vintage AM ham station today however they are seldom encountered. Probably because the early models are quite rare and the later 200 Series receivers are usually the military versions that are commonly found in an abused condition requiring extensive electronic and cosmetic restoration. When rebuilt and aligned, the Super-Pro is an incredible performing receiver with tremendous audio capabilities.

Shown in the top photo is our 1936 "Super-Pro" SP-10 SN:576 receiver that was used at WMI, a Lake Erie ship-to-shore radio station located in Lorain, Ohio. This receiver has been totally restored to original, "as delivered to WMI" condition and its performance is terrific with powerhouse audio. The lower photo is our 1937 SP-100X SN:3387 receiver that has also been totally restored to original. Performance is phenomenal and the receiver is pleasure to use. More information on the "200 Series" Super-Pro further down this webpage.

For the ultimate source of detailed  information on the Pre-WWII Hammarlund Super-Pro receivers, including Product History, Estimated Production, Serial Number Assignments, Performance and Restoration, click on "Hammarlund Mfg. Co., Inc. - The Incredible Pre-War 'Super-Pro'" in the index at the bottom of this page.  


 The Hallicrafters, Inc.  -  SX-11 

The SX-11 was a major step forward for Hallicrafters. As a continuation of the design and manufacturing style that was used with contactors, Hallicrafters' engineers designed the SX-11 to be built from purchased parts that could be assembled into a first-rate communications receiver. The SX-10 and SX-11 were the first receivers that Hallicrafters built without the use of contractors. The SX-11 boasts several firsts for the company. It was Hallicrafters' first receiver with Push-Pull audio output, first with a tuning-eye tube, first to use a separate speaker. The 11 tube superheterodyne circuit also has such unusual features as variable injection BFO, 0-200 bandspread scaling, illuminated main dial, 6L6 tubes in the P/P audio output (14 Watts of audio) plus the fabulous styling that remained in the Hallicrafters line for the next several years. The SX-11 evolved during production with early versions sporting SX-9 type knobs and several circuit differences from the later versions. From the factory, the SX-11 was housed in a metal enclosure painted black wrinkle but the advertised SX-11 was also sometimes pictured in an after-market, shielded, solid-walnut cabinet. These wooden cabinets were not a Hallicrafters' product but were available from various "jobbers" during the thirties.


1936  NC-100, sn: 334D, first production run, with the Art Deco front panel. Shown with the matching National/Rola K-10 loudspeaker

National Company, Inc.  -  NC-100 Series - "MOVING COIL" Receivers

The NC-100 was introduced in 1936 and was National's first successful receiver to not use plug-in coils. Though National's Chief Engineer and General Manager, James Millen, insisted that the best receiver performance was achieved using plug-in coils, National's mechanical engineers offered a solution with the NC-100 receiver, the first in a series of "Moving Coil" receivers. The "Moving Coil" system consisted of a movable cast metal coil box (sometimes called a "catacomb" by collectors) contained all of the coils mounted in individual shielded compartments with short contact pins mounted in molded insulators on top of the coil box.

photo above: 1937 National NC-101X  SN: 181-G

The band selector knob turned a rack and pinion gear mechanism that moved the coil box horizontally under the chassis. The coil box was supported by a rod shaft in the rear and the gear shaft pin riding in a cast slot in the front. Rotating the band selector knob would move the coil box into place, engaging the proper coil set pins into short, fixed contacts mounted under the tuning condenser. The mechanical action simulated plugging in a three coil set for each band with the ease of turning a knob while keeping all of the unused coils isolated and shielded.

The NC-100 was a general coverage receiver using 12 tubes including a cathode-ray tuning indicator that was included for AM reception. A crystal filter version was also offered - the NC-100X. In a short time a ham band only version, the NC-101X was introduced (it was within the second production run of NC-100 receivers.)  The later NC-101X receivers use an S-meter rather than the tuning eye tube. The photo to the left shows the early version of the NC-101X with the tuning eye tube indicator (SN:181-G.)

The Micrometer tuning dial, the PW-D, used on the early NC-100 is gray-blue with a red inner readout. The NC-100 Art Deco front panel was only used for a short time, ending as early as run-G. The receivers were black wrinkle finish afterwards. NC-101X receiver cabinets are all black wrinkle finish and generally use the same black PW-D dial as the HRO. All NC-100 Airport receivers had a gray PW-D installed.

There was a "reduced cost" AC-DC version "Moving Coil" receiver that was available as either General Coverage or Ham Bands only, the NC-80X and the NC-81X. These receivers feature a slide rule-type, direct-read dial rather than the PW-D micrometer dial. There was an optional power transformer available that could be mounted on the chassis to provide AC operation and isolation from the power line. The NC-80X/81X was available from 1937 to 1939. The initial selling cost was $88 but, by 1938, the price was increased to $99.

The NC-80X used ten tubes but didn't have an RF amplifier. National raised the IF to 1560kc which put the image frequency so far from the tuned frequency that it was pretty much rejected by the natural selectivity of the tuned Mixer stage. The coil catacomb is much smaller than the NC-100 catacomb since only two coils set per band are used. Since the catacomb is smaller and lighter weight, a chain drive is used to move the catacomb rather than the rack and pinion used in the NC-100. Audio output is a single 25L6.

The NC-80X never sold very well since the price was fairly high for an AC-DC type receiver. With the accessory speaker the price was over $100 and there were several receivers available in that price range that weren't so "quirky" in design. Though the NC-80X could provide excellent sensitivity and selectivity, its mechanics were "flimsy" and seemed cheap.

photo right: The NC-80X from late-1938

photo above: 1937 National RCE Airport Receiver

In 1937, the Department of Commerce, Bureau of Air Commerce contracted National to build rack mount NC-100 receivers that tuned 200kc to 400kc rather than tuning the AM-BC band. The first in the series was the RCD. The RCE (shown right) that followed had several updates to improve the receiver for airport use. By 1938, the Civil Aeronautics Authority (CAA) was created and then that government body contracted for the remaining versions of the "Airport Receivers" built by National. The CAA versions start with the RCF. The use of National NC-100-based receivers at airports continued post-WWII when some earlier versions were professionally modified into the RCP and the RCQ versions.

In June 1938, the NC-100 was given a new, direct-reading dial with mechanically articulated dial pointer that indicated the band-in-use along with a standard S-meter that was mounted behind the panel and read through an opening in the panel. The new version was dubbed the NC-100A and soon all the NC-100 series receivers featured this dial. The Crystal Filter version was referred to as the NC-100XA. The ham band "A" version was available for a while in either configuration, PW-D dial - the NC-101X - or the new, direct-reading dial version, the NC-101XA. The NC-100XA sold for $142.50 (shown in photo below.)

By 1940, the NC-200 was introduced which combined both general coverage coils and ham band coils into one catacomb allowing the users both options in one receiver and thus eliminating the need for either the NC-100XA or the NC-101XA.  The NC-200 is profiled further down this page.

The introduction of the NC-200 (in 1940) wasn't the end of the NC-100A or NC-100XA receivers however. The military had been ordering versions of these receivers since about 1939. When the USA entering into WWII, both the Navy and the Army ordered thousands of National receivers. The Army designation was NC-100ASD and this receiver had the AM BC band replaced with a 200kc to 400kc band. The Navy had the RAO Series. The versions from RAO-2 and up to RAO-9 have two RF amplifier stages for maximum reduction of LO leakage to the antenna. The Navy also ordered the RBH receiver with better coverage of the medium wave bands due to its 1500kc IF. See "WWII Receivers and Post-War Ham Gear" webpage for more information on these WWII versions.


For the ultimate in detailed information on the NC-100 Series "Moving Coil" receivers, including Airport Receivers, Military Receiver versions, serial number analysis and restoration suggestions, go to our web-article "National NC-100 Series - Moving Coil Receivers" - navigation link below.

Why did James Millen Leave National? - James Millen left National in May 1939, officially to form his own company, James Millen Mfg. Co., but here's what Millen himself had to say about his leaving, as told to John Nagel K4KJ and reported in his "Brief History of the National Company, Inc."

National had been successfully building its reputation as a top shortwave communication receiver company. The sales and designs coming out of National were at the cutting edge. Unfortunately, the majority share holder at National Company, one Warren Hopkins, wanted National to suddenly change directions. Hopkins wanted Millen to switch emphasis from shortwave communications equipment and go into the consumer "home radio market." Hopkins thought this change would expose more of the public to National products by supplying "Wards" or "Sears" with home radios. Millen was adamantly against National changing direction. He had worked for the past eleven years to put National as the leader in shortwave communication receivers and, to Millen's dismay, it seemed that Hopkins (and perhaps some others in the company) wanted to abandon this successful business position. Millen resigned but National never went into the home consumer radio market at that time. Demands from WWII in Europe resulted in huge orders for HRO receivers which rendered the argument for change moot. Years later, in retrospect, Millen believed that Hopkins' position stemmed from a desire to maximize his stock value because of his health issues and had nothing to do with National's long-term success.

Another version was related to me by George Meier based on what some of Millen's close friends told him.

It seems that Millen had gone to Washington D.C. to discuss the use of the HRO receiver in the military. At the meeting, Millen supposedly represented himself as president of National. Millen's "high profile" at National (and in National's advertising) did seem to promote the belief that Millen was "in charge" so apparently the "Washington crowd" believed that they were dealing with National's CEO. Somehow word got back to William Ready (the actual president of National Company) who was livid. During the meeting at National (upon Millen's return) Millen was asked to resign, which he did. It seems like an over-reaction on Ready's part, especially since the National-Millen publicity promoted "Millen as CEO" through most of the thirties.

This Washington DC story has some problems however. Millen was de facto running National. If it had been a problem for William Ready, one would think he would have brought it to Millen's attention years earlier. Millen was "high profile" because he literally was the only one at National that communicated to the amateur public. Millen actually personally answered many of the letters that came into National from hams around the country. He had a monthly open letter to hams that ran in QST magazine. Millen personally traveled around the country visiting hams and gathering information on what hams wanted from National. According to John Nagel, Millen along with his personal assistant, Frances Bearse, really did "run" National in the thirties. If Millen had represented himself as National's president in Washington D.C., it doesn't seem like it would have been much of a problem since he was, in fact, running the company.

To leave the successful position that Millen had at National, with his very "high profile" personality, must have been the result of a serious internal conflict. However, one should remember that Millen was still a young man when he left National. Perhaps the conflict with Hopkins was enough to force Millen's resignation and allow him to become the CEO of his own company, James Millen Mfg.Co. and not have to deal with the "Hopkins" of the corporate-world.


Sears-Roebuck - "Silvertone"  Model 5656A, (Howard Radio Co.) 

During the thirties, even Sears-Roebuck got into the communications receiver market by offering their Silvertone Model 5656A, built by Howard Radio Company in 1937. The receiver was an eight tube superhet with three tuning bands covering .55 to 18.0 MC. Also included was variable coupled IF for adjustable selectivity, an eight inch diameter tuning dial with multi-colored scales that somewhat compensated for the lack of a bandspread, an AVC switch with separate Sensitivity Control (IF Gain) and a built-in 8" Jensen speaker. It is likely that the screen-grille was originally flocked with some kind of mohair - this was typical of the screen grilles of the day. The BFO was built on a separate small chassis. The 5656A provided the basic ham necessities and performance was surprisingly good with sensitivity and stability that was hard to find - even in more expensive receivers. 


Patterson Radio Company, Pierson-DeLane Company  -  PR-15

The PR-15 receiver was designed by Karl Pierson in late-1936 for Patterson Radio Company. Pierson had designed the Patterson PR-16 in 1935 and it was a fairly successful receiver. It had its quirks, such as the parallel-connected RF amplifiers that allowed Patterson to advertise the receiver as having "two RF amplifiers" and yet only have a single set of RF coils making the PR-16 essentially a single pre-selection receiver. However, the PR-16's powerful audio section sold the receiver and its performance was more than adequate for most hams. Karl Pierson had designed the PR-16 in just a few weeks, rushing it into production to get Emmitt Patterson "off the hook" for the PR-12 Communications Receiver debacle. Pierson decided that his next design was going to have up-to-date circuits, great bench presence and modern performance. Thus the PR-15 was born.

Using 15 tubes, the PR-15 circuit features double preselection on all bands (two TRF amplifier stages,) two IF amplifiers operating at 465kc, Crystal Filter, a tuned Noise Silencer similar to the Lamb Noise Silencer, an Interchannel Noise Supressor (aka Squelch,) Red and Green lamps to indicate "Transmit" and "Receive," fixed bias on first AF amplifier grid provided by a battery cell, push-pull audio output using a pair of 6V6 tubes, fold-down stand that elevates the front of the receiver for better visibility of the controls, magnifying lens for logging scale, vernier tuning and a carrier level meter (R-meter.) The "Communication" switch had a "Monitor" position that was supposed to allow listening to the station transmitter through the PR-15 speaker or headphones. Overall, the PR-15 was a very competitive receiver with performance capabilities equal to the top-of-the-line products from the "Big Three," that is, Hallicrafters, Hammarlund and National. 

Pierson left Patterson Radio Company in 1937 and simultaneously purchased all of Patterson's communications receiver manufacturing business, including the rights to continue building the PR-15. Since assembly of the receiver was accomplished at the Gilfillan Brothers plant in Los Angeles, the transfer of Patterson's communications business to Pierson really didn't affect the construction of the receiver. Other than the name change to Pierson-DeLane (after Pierson partnered with his investor, business adviser and VP, a Mr. DeLaplane,) the PR-15 appearance remained unchanged although there are a few examples around that are gray rather than black wrinkle finish. Pierson continued to build the Patterson PR-15 under the Pierson-DeLane name until about 1939. Pierson-DeLane then started manufacturing two-way radios up until they went out of business in 1943. Emmitt Patterson continued to build some consumer radios but eventually quit the radio business entirely in 1939.

Note that this PR-15 (it's a Patterson) doesn't have the manufacturer's name on the dial. Instead the original owner's name, ~ Charles Morrison ~, has the place of honor. Charles Morrison was W6JVJ and lived in and around Los Angeles, California. He had been a professional shipboard radio operator in the late-twenties and saw duty on the S.S. City of Los Angeles and possibly also on the S.S. City of Honolulu. Both ships were owned by the Los Angeles Shipping Company and were passenger ships that sailed between LA and Honolulu. Morrison moved to New Mexico in 1930 to work for Western Airlines but was back in LA within a few months, working for Pan-American Airlines. Morrison had an earlier, two letter ham call that is unknown. Morrison was an active ham into the 1990s. Exactly how Charles Morrison managed to have his name applied to the dial is unknown. Upon close examination after cleaning, it appears that the company name was never applied and that " ~ Charles Morrison ~ " (hand-lettered in matching silver paint) was applied at the factory during assembly of the receiver. Since Morrison lived in Glendale at the time (just outside Los Angeles) perhaps he was able to order the PR-15 directly at the factory and was able to have the dial for the receiver "customized." The factory, of course, was the Gilfillan plant. Guy Morrison, Charles Morrison's son, donated his father's Patterson PR-15 receiver to WHRM in 2018.


Utah Radio Products Company  -  UAT-1 "Add-A-Unit" Amateur 80 Watt Transmitter Kit

Utah Radio Products sold many different types of radio components from the 1920s up into the 1950s. Although mainly known for loudspeakers in the 1920, Utah also produced various type of transformers and chokes along with many other radio components. In 1937, Utah introduced the "Add-A-Unit" series of transmitter kits. There were five different kits that could be purchased with the designation being "Kit No.1," "Kit No. 2," etc., up to "Kit No. 5."

Kit No. 1 was an 80 Watt input power transmitter that used a metal 6L6 crystal controlled oscillator and two parallel connected metal 6L6 tubes as the PA. Plug-in coils had to be wound as part of the kit construction with plans for coil sets covering 160M, 80M, 40M and 20M. Additionally, Utah would supply construction details on 10M coils on request. Three coils comprise each set with an oscillator coil, a PA input coil and a PA output coil. Four pin Hammarlund forms are used for the oscillator and PA input coils and a Hammarlund large five pin coil is used for the PA output coil. The PA output is link-coupled to either an antenna that is cut for a specific operating frequency or to an antenna matching device. Power supply is built-in and uses all Utah "iron." Price was $49.75

Kit No. 2 was a 50 Watt Modulator priced at $44.50. Kit No.3 was the Antenna Coupler priced at $13.95. Kit No. 4 was a 500 Watt input RF amplifier priced at $49.75. Kit No. 5 was a 250 Watt Class B Modulator priced at $49.75. When all five kits were assembled together, the builder ended up with a 500 Watt AM-CW transmitter.

The idea of "Add-A-Unit" was driven by the Depression and the fact that most hams didn't have the money to purchase all of the kits simultaneously. A prospective builder could start with Kit 1 and probably Kit 3, which would result in an 80 Watt CW crystal-controlled transmitter that could be matched to several types of antennae. Later, Kit 2 could be added for AM operation. Then perhaps last, Kit 4 and Kit 5 could be added giving the builder a complete 500 Watt AM-CW transmitter with the purchase spread out over the time necessary.

Shown to the left is the UAT-1 80 Watt transmitter and a copy of Kit 3 Antenna Coupler. The coupler requires balanced feed line going to a dipole antenna. I usually can get about .6amps of RF antenna current. I had a two-way QSO with K7RLD (Washington state) with this set-up. K7RLD was using his Utah UAT-1 transmitter. Probably the first two-way UAT-1 QSO in several decades.


Breting Radio Mfg. - Breting 14 

Introduced in 1937, the Breting 14 offered the user spectacular styling with great performance. Some of the features were two RF amplifiers (although the first RF amp is an untuned pre-amp switched in above 7MC,) Crystal Filter and front panel adjustable BFO (although it is actually one of the small levers projecting from under notches at the bottom of the front panel.) There were also inputs allowing the ham owner to use the receiver's high fidelity audio section as a transmitter modulator speech amp. Designed by Ray Gudie and selling for just over $100, that price also included a chrome-plated chassis and P/P audio with 6F6 driver and P-P 6F6 output tubes. The bandspread is accomplished mechanically using a slow-motion control coupled to the main tuning drive and operated using the knob on the lower right of the panel. The magnificent mirrored dial inside an art deco bezel also featured an edge-lighted translucent plastic tubular dial scale for band-in-use readout and a red pointer is backlit onto the logging scale. The "R" meter is also an edge-illuminated translucent scale. Certainly the dazzling dial illumination during operation gave the Breting 14 an impressive appearance that was matched by the receiver's great performance. In 1938, minor circuit modifications prompted a designation change to Breting 14AX. The most obvious of the AX differences are the two additional knobs on the front panel that replace the older levers that protruded through slots under the panel of the Breting 14. Some Breting 14AXs were painted gray. Paul J. Breting started selling receivers in 1935 but his receivers were assembled at the Gilfillan plant, in Los Angeles, since Breting didn't have the required RCA license.* Breting went out of business in 1940. Interestingly, the Breting 14 dial bezel is the same bezel Patterson used on their PR-15 (profiled above.) Parts sharing, courtesy of Gilfillan's stock room apparently.


Bliley Electric Company

Did you ever wonder what the granted ham frequencies were before WWII? Shown to the right is a 1939 multi-color chart put out by Bliley Electric Company, the famous quartz crystal manufacturer.

160M band shows 1750kc up to 2050kc. It was the popular Phone band because it could be used by newly licensed hams (Class B.) 50kc was CW only. The 1936 ARRL HB shows the lower end of 160M as 1715kc at that time.

80M was the same frequencies as today but was CW only except for 100kc Phone for Class A licenses.

40M was the same frequencies as today but was totally CW only.

20M covers 14.0mc up to 14.4mc and only had a small 100kc section for Class A Phone. The remaining 300kc was CW only.

10M was from 28.0mc up to 30mc and allowed Class B licenses to operate Phone from 28.5mc up to 30mc. 500kc was CW only.

"Restricted Phone" indicates Class A license. "Unrestricted Phone" was for Class A or Class B licensees. Class A required one year experience and a more difficult test. Class B required no experience and a less difficult test. Class A, B or C had a 10wpm code test requirement. Class C license was the same privileges as Class B but testing was administered by mail and volunteer examiner.


 The Hallicrafters, Inc. - Skyrider Diversity DD-1

In 1936, James Lamb and James McLaughlin custom-built an elaborate dual-diversity receiver for XE1G, Dr. James Hard, a wealthy and enthusiastic ham in Morelos, Mexico. In 1937, McLaughlin and Karl Miles, Chief Engineer for Hallicrafters, designed a version of the XE1G receiver for production. Hallicrafters began advertising the Dual Diversity DD-1 in June 1938. The dual diversity design utilized a shared local oscillator to provide single dial tuning which drove the seven-gang tuning condenser. Main tuning is accomplished with the left-side dial and bandspread uses the right-side dial. The massive Yaxley-built push-button switch assembly controlled AC power and bandswitching. The four meters monitored signal levels in each receiver, the signal balance between the two receivers and the common AVC line in S-units. 26 tubes are used in the DD-1, including the four VHF 1851 RF amplifier tubes which allowed the receiver to tune up above 40MC.

The table version was to sell for about $300 for the basic receiver without the Power Supply, Power Amplifier, Diversity Action Meters or speaker, (these accessories increased the basic price by $120.) The DD-1 Console version included the fabulous 15" Jensen Ortho-Dynamic High Fidelity Speaker in a Hagstrom-designed Deco-styled Bass Reflex cabinet along with a matching wooden top housing the diversity action meters. The DD-1 Power Supply and Power Amplifier chassis were stowed on shelves built into the rear of the speaker console. The DD-1 Console was priced at $500 - nearly the price of a new Chevy coupe in 1938. The prices escalated to $627 for the table version and an incredible $720 for the second production run models sold in 1939.

Not surprisingly, the DD-1 was only seriously advertised for about six months (last QST ad was 1/39) but the DD-1 was shown in the Hallicrafters' line-up in the 1940 ARRL Handbook. Total production is thought to be around 120 receivers. As a specialized receiver it confirmed that Hallicrafters' engineers were capable of sophisticated designs but this "over-the-top" creation certainly wasn't what the Hams of the late thirties would have purchased for their station receiver.

The DD-1 shown to the left is SN 80596, the highest known serial number from the initial production run. This DD-1 was on display in our Western Historic Radio Museum from 2002 until we closed the museum in 2012. It is shown as it now looks in its new nook located at our new QTH in Dayton, Nevada.

  For the ultimate information source on the Skyrider Diversity DD-1 including Estimated Production, Serial Number Assignments, Performance, Known DD-1 Serial Numbers, Photo Gallery of other DD-1 receivers, History of Diversity Reception plus many details on our Restoration of our DD-1 on "Hallicrafters DD-1 - Restoration and History of Diversity Reception" at the bottom of this page.   



 SP-200SX - 1.2MC to 40MC - Early version from 1939

Hammarlund Mfg. Co., Inc.  - "Super-Pro" - SP-200 Series  

Introduced in October 1939, the SP-200 series offered the same uncompromising quality of its predecessors while thoroughly updating the receiver to 1940 design specifications and reducing the cost of production so the receiver could list for about $315. Some of the changes from the earlier Super-Pro was the redesign of the IF amplifier section to use three stages followed by a conventional duplex diode detector tube, the 6H6. Additionally, the amplified AVC circuit was simplified with capacitive coupling pickup and reduction of the transformers to one unit. 16 metal octal tubes were used in the new receiver with two glass rectifiers in the power supply bringing the total to 18 tubes. The new Super-Pro still featured double preselection on all bands, variable coupled IFs (variable bandwidth) but added an improved Crystal Filter, a new illuminated S-meter with 0 to 9 scale that was connected to the AVC circuit so it worked normally (the early Super-Pro "Tuning Meter" measured total IF plate current and worked "backwards") and a brand new Noise Limiter circuit. The powerhouse audio still used triode connected P-P 6F6s w/ 6F6 driver and produced up to 14 watts of high-quality audio power. The suffix letters designate the frequency coverage with X (.54-20MC), SX (1.2-40MC) and LX (100-400KC and 2.5-20MC) models, (all SP-200 series receivers had a Crystal Filter and therefore the "X" option.) Early versions of the SP-200 feature a Speaker/Phone switch, standard vertical mount audio transformers with 8 ohm audio output Z and a wrinkle finished aluminum front panel. Later versions have a front panel phone jack, potted audio transformers with dual outputs (600 ohm speaker and hi-Z phones) and semi-gloss finished steel panel (the front was copper-nickel plated under the paint for corrosion protection.) The separate power supply was updated to eliminate the field coil requirement on most models. Some sales information will denote the speaker size by using variations in the model number, e.g. SP-210 (10" speaker) or SP-220 (12" speaker) however, Hammarlund always used "200 Series" in their advertising. By 1942, a matching speaker cabinet, model PSC, was listed separately at $5.10, which implies that the speaker was still being supplied without a housing. Hammarlund also indicated in their advertising their willingness to supply the Super-Pro in any special frequency requirement per customer request and special order. 

1941 SP-200LX - later version with a steel panel painted semi-gloss black

The most commonly heard complaints about the Super-Pro receiver involve limited frequency coverage. Though this is somewhat true, one should bare in mind that the Super-Pro was a commercial/military receiver that could also be used by hams. Hammarlund offered the "ham version" of the Super-Pro in the "SX" option - 160M to 10M coverage. Most of the limited frequency coverage complaints were from hams who wanted the SX version but could only find the X or L versions. Long warm-up time was another complaint with ~2 hrs. required for minimal drift - but most pre-war receivers won't quit drifting any sooner, if ever! Besides, the SP-200 was designed to be left on continuously which eliminated the drift issue. The non-calibrated 0-100 scaled bandspread dial brought more negative comments but since the Super-Pro was a commercial/military receiver also, it might be used anywhere in the frequency ranges so a calibrated bandspread wouldn't have been practical. Another common complaint was that high front-end tube noise limited the ability to copy very weak signals but this often-heard opinion was based on a popular modification article that appeared in CQ magazine, advocating replacing the front end tubes with miniature tubes (along with several other unnecessary modifications.) Actually, using a matched (or tuned) antenna would have been an easier solution. A matched antenna will help considerably in reducing noise and increasing signal strength. The Super-Pro does not have an antenna trim control and depended on the user to provide a matched antenna for best performance. Also, many users ran the receiver with entirely too much RF gain and too little AF gain resulting in high noise that tended to mask weak signals. The solution was to operate the receiver as a "communications receiver" and not as a "broadcast radio."

Today, the Series 200 Super-Pro is rarely encountered as the station receiver in a Vintage Ham Shack, probably from the many years of negative comments from hams who wanted to use this military/commercial receiver in their ham station and expected the receiver to have been designed exclusively for ham use, which it wasn't. The majority of SP-200 receivers encountered today are the WWII military versions and they have had years of hard use and probably a lot of abuse. Normally found in "rough" condition, the Series 200 Super-Pro will typically require total restoration to function at it design limits. When fully restored and aligned, the SP-200 series receivers are unbeatable performers. The military Super-Pro 200 Series receivers are generally identified with their Signal Corps designations of BC-779 (LX), BC-794 (SX) and BC-1004 (X.) These versions are more or less identical to their civilian counterparts. More information on the military Super-Pro receivers on the "WWII  Receivers and Post-War Ham Gear" webpage.

For the ultimate source of detailed  information on the Pre-WWII Hammarlund Super-Pro receivers, including Product History, Estimated Production, Serial Number Assignments, Performance and Restoration, click on "Hammarlund Mfg. Co., Inc. - The Incredible Pre-War 'Super-Pro' Receivers" in the index at the bottom of this page.


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Hammarlund Mfg. Co., Inc.  -  HQ-120X 

Hammarlund realized that the Super-Pro was far too expensive for the majority of hams and that it was really a commercial-professional receiver that wasn't specifically designed just for the ham market. So, Hammarlund designed and built a receiver that was designed just for the ham market, the 12 tube, HQ-120X, (introduced in 1939.)  To keep the selling price within the typical 1939 ham's budget, the circuit uses a converter tube, single pre-selection, single-ended audio and a built-in power supply but frequency coverage was .54 to 30MC and ham band calibration was provided on the bandspread dial (generally credited as the first ham band calibrated bandspread available.) Selling price listed at $230 but the receiver usually sold for around $190 (or less) from most dealers. The HQ-120X was popular and provided decent performance on shortwave and ham bands up to about 15 Mc. Beyond that, images and lack of sensitivity become a problem. Late in production, a special gray painted version was offered. The U.S. Navy also had versions built and designated as the RBG or CHC-46140, though the tube line-up is slightly different from the civilian HQ-120X. The HQ-120X was the first of a long line of "HQ" receivers built by Hammarlund specifically for the ham market. Shown in the left photo is a black finish HQ-120X with the unusual rack-mount option with an extended front panel and rear dust cover but with feet on the bottom to allow table-top use. The right photo shows the HQ-120X in the standard table cabinet with the later production gray finish option. By 1942, the gray finish had become standard and black finish was a special option.


Meissner Manufacturing Company  -  Traffic Scout  -  Kit No.10-1169

Meissner Manufacturing Company offered the Traffic Scout only in kit-form. The receiver featured Meisnner IF transformers along with a pre-assembled and aligned front-end. This eased the requirements for the average "kit builder" in that sophisticated test equipment wouldn't have been necessary to complete the receiver assembly and have it operate correctly. Nine tubes were used in the Traffic Scout circuit providing single-preselection, two stages of IF amplification and a single 6V6 audio output. The new VHF/TV tube, the 1853 was used as the RF amplifier (this tube was later identified as the 6AB7.) The 6Q7 duplex diode-triode tube provided the second detector, AVC and 1st AF amplifier functions. A Meissner crystal filter, Meissner BFO and electrical bandspread were included in the design. IF was 456kc. Five tuning ranges spanned .53mc up to 32.4mc. Both RF gain and AF gain controls are provided along with a variable Tone control that also functioned as the AC power on-off switch. A front panel Standby switch was also provided. The power supply has standard chokes within the circuit so that a regular PM loudspeaker can be used although the audio output transformer must be mounted on that speaker (receiver connections are B+ and 6V6 plate.)

Meissner offered the buyer a few options when purchasing the Traffic Scout kit. The complete kit including cabinet and panel was identified as Kit No.10-1169 and the selling price was $65.10. The Traffic Scout kit without the cabinet or panel was identified by Meissner as Kit No.10-1170 and sold for $58.50. The panel by itself was $2.10 and the cabinet by itself was $5.10. These were net prices and options shown in the 1940 ARRL Handbook with "list" prices being much higher. List for the complete kit, No.10-1169, was $108.50. The Traffic Scout cabinet is fairly large with dimensions of 10.5"H x 19"W x 13.75"D and the weight of the complete receiver is about 35 pounds. The photo above shows the Traffic Scout out of the cabinet. The cabinet is awaiting restoration (paint.)

The manual recommends that the IF transformers be aligned since the Crystal Filter provides a very narrow bandwidth on 456kc. It would be fairly easy to provide an accurate frequency from a test oscillator by "sweeping" the IF to determine the exact crystal frequency. Then the IF transformers would be aligned to that signal frequency. The manual continues in stating that unless an accurate signal generator is used for RF tracking alignment, it's best to leave the front-end with the factory alignment. Typical of pre-WWII ham radio kits, the Traffic Scout instructions are not very detailed (compared, for example, to the typical Heathkit instructions.) An excellent drawing of the underneath of the chassis was provided along with a schematic. The remaining instructions are written in the order that the receiver should be assembled. Complete instructions are written within a few pages and then the drawing and schematic. At the time, building or homebrewing was part of being a radio amateur. The advantage of the typical ham radio kit was that all of the sheet metal work that would require expensive tools was already done. Alignments that required expensive, precision equipment were already done. That left the kit builder with just the task of assembly, wiring and basic testing to then have a professional-looking, decent-performing receiver. It also gave the kit builder the "bragging-rights" that his receiver was "home-built."


The Hallicrafters, Inc.  -  SX-28 & SX-28A

The masterpiece of pre-WWII Hallicrafters receivers. Introduced in July 1940, the SX-28 circuit boasted 15 tubes, covered .55 to 43MC in six bands, had P-P audio, ham band calibrated bandspread, Lamb Noise Silencer, Amplified AVC, on and on. Hallicrafters advertised that the SX-28 had been designed by 12 of their engineers based on 600 requested reports including input from the Government. The styling was beautiful and the performance incredible. Early versions of the SX-28 have gray panels but starting in 1941 the panel color was changed to black. About the same time the Lamb Noise Silencer was redesigned. A few months later the bandspread gearbox was replaced with a dial string drive. There were many engineering design changes throughout production. During WWII, Hallicrafters continued to redesign portions of the SX-28 and, in April 1944, a major redesign to the receiver's front-end prompted a designation change to SX-28A. The old front-end coils were replaced by smaller, Hi-Q Micro Set types that were mounted on removable chassis. The new coil design eliminated the majority of brass parts that were used in the early style coils. After WWII, Hallicrafters had nothing new to sell the hams as they had devoted all design and manufacturing to the war effort, so they offered the SX-28A as a 1946 model. The last 4000 SX-28As built have "SX-28A" indicated on the front panel (indications are that the "A" appeared around September, 1945.) Hallicrafters published that 50,000 SX-28s (and SX-28As) had been built by 1946, however the serial numbers seem to indicate a production figure of about half that amount, around 27,500 receivers. Nowadays, many SX-28s and SX-28As are still being used in vintage AM ham stations because of their fabulous audio quality and classic "good looks." Most ham AM operators find the sensitivity, selectivity and stability quite acceptable for communications on vintage AM nets today. The SX-28 (SN H-151197) shown above belonged to W3ON, John Ridgway (SK), who purchased it new in February 1942. In 1997, at age 85, John sold his receiver to me saying, "'s so damn heavy, I can't even turn it on its side anymore." The W3ON SX-28 is in superb, all-original condition and is an excellent example of how the pre-WWII SX-28 looked when new.

For the ultimate source in detailed information on the SX-28 and SX-28A history, production and engineering changes, dating by serial number information, competition comparisons click on "Hallicrafters SX-28, a Pre-war Masterpiece" at the bottom of this page 

The Hallicrafters, Inc. - SX-28 and R-12 Bass Reflex Speaker

During early production of the SX-28, three different speaker options were offered. The PM-23 was a 10" speaker in a table top, metal case. The R-8 was a small bass reflex cabinet with 8" speaker and the largest speaker offered was the Hallicrafters-Jensen Bass Reflex floor speaker, the R-12. Selling price was $29.50 and, together with the $159.50 that the SX-28 cost, represented quite a substantial investment in 1941. The R-12 uses a Jensen 12" PM speaker with 5000 ohm to 8 ohm transformer. The cabinet is constructed with panels made from solid lumber core with soft wood veneer. Paint was a dark silver color except for the decorative incised arch over the speaker opening that was filled with red paint. The cabinet panels are held together entirely with small internally mounted clamps. This method of assembly allowed the speaker to be shipped in a flat box. Originally, the wire screen grilles were flocked with a champagne colored mohair but most surviving examples have lost their flocking with years of use.

The SX-28 (SN H-130170) & R-12 combination shown to the left was purchased as a "set," new in mid-1941, by W6ANX, Theron "Woody" Woods. The combo was found in the basement of Wood's house in Auburn, California around 2004. The R-12 was in dismal condition with warped boards and missing veneer. The receiver functioned but not as it should have. Rebuilding the R-12 required total disassembly and straightening the panels. The straightening process involved wetting the panels and then clamping them to flat surfaces until thoroughly dry. After this, the soft-wood veneer pieces were glued and new pieces glued to replace the missing pieces. The paint was matched from the protected paint on the "h" grille. I didn't bother with the flocking of the grille screens since all of the R-12s I've seen don't have any flocking anymore. Also, it would have required mixing up a batch of special color felt that probably wouldn't have looked right anyway.

H-130170 was completely rebuilt. Only one strange problem was found. The slug of the third IF transformer had come loose and was at the bottom of the slug barrel. Since this transformer is a capacitive adjustment, the IF would peak but it was not really tuned. The output level was far below normal which was the clue that something was wrong. I replaced the transformer with a good one from a parts set. Both H-130170 and its matching R-12 sound incredible now with loads of bass response and great performance.

Want to build a replica R-12 speaker? I took this R-12 apart and photographed the interior in detail. I also measured all of the important dimensions and described the types of materials used in the original construction. Still interested? Phil Nelson of "Phil's Old Radios" has edited and hosts the article on his website. Here's a link to the article:  Build Your Own Hallicrafters R-12


Silver Anniversary NC-200   (SN: C-536)    ca: Jan.1941

National Company, Inc. - NC-200 "Moving Coil" Receiver

National had great success with the "Moving Coil" receivers that used a coil "catacomb" band changing mechanism. However, the NC-100XA, was a general coverage receiver only with no band spread capabilities and the NC-101XA was a "ham bands only" receiver. National engineers essentially combined the features of both receivers into their new, 1940 model, the NC-200. Introduced in October 1940, the NC-200's appearance was strikingly different from the former, all black wrinkle finish, cabinet models. Following the trend of offering gray painted cabinets as options or as the standard finish, National decided to offer even more with a two-tone gray cabinet with the dark gray in wrinkle finish and the lighter gray in smooth finish. The cabinet was trimmed with dual "wrap-around" chrome bars. Large sheet metal louvers were incorporated into each side of the cabinet. The matching loud speaker featured the same two-tone gray paint trimmed with chrome bars. Inside was a 10" diameter Jensen PM speaker.

The NC-200 circuit featured several improvements over its older brothers from the NC-100 family. The coil catacomb reduced the size of each coil chamber and that allowed squeezing in one more tuning range for a total of six general coverage bands spanning 490kc up to 30.0mc. By adding two more stub-pins to the contacts of each of the coil assemblies, a band spread function could be realized. This feature was added to the four upper ranges of the general coverage bands, allowing band spread coverage of the 80M, 40M, 20M and 10M ham bands. To change bands required the user to pull on the main tuning knob. This disengaged the tuning and engaged the pinion gear into the rack gear for changing bands. One full turn would change bands for general coverage. Between the upper bands, one could select a position "between" the one turn rotation (about one-quarter turn) where the band spread pins engage. This would allow the receiver to then operate in band spread for the particular ham band selected. To ease the operator's identification of which band had been selected of the ten ranges available, a dual articulated flag system was viewed thru slots that flanked the tuning dial pointer hub.

Some of the tubes that had been used in the NC-100XA were updated in the NC-200 circuit with the most obvious change being the replacement of the push-pull 6F6 tubes with push-pull 6V6 beam-power pentodes delivering about 8 watts of audio power. Additionally, the RF amplifier and one of the IF amplifier tubes were changed from 6K7 tubes to 6SK7 tubes. AVC and BFO functions used 6SJ7 tubes to replace 6J7 tubes. The old 80 rectifier was replaced with a 5Y3G. The NC-200 eliminated the interstage coupling transformer formerly used and replaced it with a phase-inverter circuit that repurposed one of the triodes of the 6F8 tube. Twelve tubes total were used in the NC-200's single-preselection superheterodyne circuit. The IF was changed from National's usual 456kc to the industry standard 455kc. A new 455kc Crystal Filter was incorporated into the circuit and featured a six-position switch to select various stages of selectivity along with a Phasing control. The S-meter used a new Marion Electric model that had a square flange although the scale inside is the same as the older, round flange meters. The S-meter toggle switch that was used on the NC-100A receivers was replaced with a switch that was incorporated into the RF Gain control. Only when the RF Gain was at maximum (full CW) was the S-meter switch actuated (of course, the AVC had to be switched on for the meter to read signal strength.) A series valve (clipper) type Noise Limiter and a variable Tone control were also part of the circuit although both of these improvements had been incorporated into the last of the NC-100XA receivers. Battery operation was possible utilizing the seven pin auxiliary socket located on the rear apron of the chassis. The NC-200 sold for $147 in 1940. National listed the models as NC-200TG (without matching speaker) or NC-200TS (with matching speaker.) Also, with R substituted for the T if the model was rack mount style. There was also a "TGM" version that eliminated the bandspread and was probably for commercial or military applications.

Most of the pre-war NC-200 receivers were built within two production runs identified by letter prefixes and starting with the letter C. Run C, probably started in September 1940 and probably produced just under 1000 receivers since the serial numbers go up into the mid-900s. Run D probably started around mid-1941. It also seems to have produced fairly high quantities of NC-200 receivers, probably around 800 to 900 receivers. Run E was probably started sometime in 1942 and ran thru most of WWII. Run E was used for the remainder of the NC-200 family which included the WWII NC-200FG that eliminated the ham band spread feature. This receiver later became the NC-240C. When the AM BC band was replaced with a 200kc to 400kc band, the receiver was designated NC-240CS. Production run F seems to have been shared with the NC-240CS and the post-war NC-240D (early versions only - later NC-240D receivers use a seven digit SN.) Ultimately, around 1800 pre-war NC-200 receivers were probably produced thus making those versions fairly uncommon.

Silver Anniversary NC-200 - In December 1940, National introduced the Silver Anniversary NC-200. But,...whose anniversary was it? Surprisingly, it wasn't National's. December 1940's QST was a special issue that celebrated QST's "Silver Anniversary" (25 years) with a silver cover on the magazine and with the inside loaded with articles on the origin of ham radio, the ARRL and QST. On the back-inside cover, National had a full-page ad that introduced the Silver Anniversary NC-200. The ad states that this special version of the NC-200 was "Dedicated to amateurs on the twenty-fifth anniversary of their own QST. A toast to QST, the ARRL and the Amateur!" This version of the NC-200 had a special NC-diamond insignia installed that had "SILVER ANNIVERSARY" embossed around the perimeter. The special NC-diamond was also installed on the matching loudspeaker housing. Additionally, the receivers were equipped with special brown bakelite knobs and a brown bakelite S-meter housing. Also, the special NC-diamond, the tuning knob's skirt and all of the control nomenclature plates were finished in "gold tone." National wasn't consistent in the Silver Anniversary trim however and some receivers will be found with off-white or cream color dials, black knobs or a very light gold tone finish. Only the "Silver Anniversary" insignia remained consistently installed throughout production. Silver Anniversary NC-200 receivers were built during the early-production of run "C" and into mid-production of run "D." Though it would seem like both Standard Finish and Silver Anniversary models would have been available during this time period, it's very possible (and reported serial numbers seem to confirm) that only Silver Anniversary models were produced for a considerable time period. Shown above is a Silver Anniversary NC-200 model with the serial number C-536 and probably dates from early-1941.


*RCA Superheterodyne License and Gilfillan Bros., Inc.

In the 1920s, the "Radio Group" (an un-official name for the cross-licensed corporations -  General Electric, Westinghouse, AT&T, United Fruit Company and RCA) had control over most of the important radio patents and had excluded all non-licensed companies from building superheterodyne receivers by threats and law suits. RCA began licensing out TRF circuits (that had been purchased from Hazeltine) in the late twenties.

Early in 1930, the government filed an anti-trust suit against the "Radio Group" essentially taking control (and patents) away from GE and Westinghouse. RCA was given the Superheterodyne Patent at that time as part of the settlement. The settlement also stipulated that RCA would now have to license other manufacturers to build superhets. Every major radio company had to have the RCA Superheterodyne License in order to remain competitive even though there were royalities and other conditions with having the license. Some of the conditions required that license holders had to produce radio chassis in sufficient quantity and of high quality in order to qualify for the RCA license. This left many small companies unable to qualify for the license due to their limited market, small overhead and the expenses involved in producing high quantity and high quality chassis.

Fortunately, for the small radio companies, there was a option in the RCA license rules and conditions that allowed a license holding company to build chassis for other un-licensed companies. Gilfillan Bros., Inc. in Los Angeles, California had the only RCA Superheterodyne license on the West Coast (exclusive license holder for 11 Western states.) This arrangement was due to a 1928" face to face" confrontation between S. W. Gilfillan and David Sarnoff, (who admired Gilfillan's determination.) At the time of the Sarnoff-Gilfillan meeting, James G. Harbord (RCA President from 1922 to 1930) had taken a leave of absence to campaign for presidential-candidate Herbert Hoover and that left general manager, David Sarnoff, in charge. The Sarnoff-Gilfillan arrangement was the offer of exclusive RCA licenses in exchange for closing all Gilfillan operations not in the Western States. Specifically, the Gilfillan plants in Kansas City and New York City were the apparent target of the agreement. At the time, this licensing was mainly for TRF circuitry but, in 1931, the superheterodyne was added to Gilfillan's exclusive licensing.

Gilfillan allowed subcontractors to build their own chassis on the second floor of the Gilfillan plant. This included Los Angeles companies such as Patterson, Breting, Jackson-Bell, Packard-Bell and Pierson-Delane along with dozens of other smaller companies, all in the Los Angeles area. During the early 1930s, the policy was not very strict and the radio didn't have to be assembled by the licensed company. The subcontractor was protected because he was building the radio using parts supplied by the licensee and the building process was supervised by the licensee. Some companies (including Gilfillan) allowed sub-licensed companies to supply their own assemblers, set up their own production lines, utilizing plant stock and tools, using plant floor space at the license holder's company. The sub-licensing policies allowed many small radio companies the start-up operations because the major expense, that is, building a factory, real estate, equipment and stock expenditures were eliminated. This left the new radio company/sub-contractor to only have to hire personnel and have a good design to build. During the depression, this really was the only option for a small company to produce quality radios, be able to sell those radios and profit from that business. Also, those profits were shared by the licensed company (5% to Gilfillan which they split with RCA.) The subcontractor licensing allowed everyone involved to profit during the difficult economic times of the 1930s.

In 1940, RCA decided that there was not enough quality control on the chassis produced for the smaller companies by the license holding companies and began to stop allowing the sub-licensing option. The RCA license structure was also changed at that time to allow most smaller companies to obtain their licenses direct from RCA.


1. "Communications Receivers - The Vacuum Tube Era, 1932-1981"  by Raymond S. Moore - Undoubtedly the best reference book on tube-type superheterodyne communications receivers. History of receivers and the companies along with circuit description and photos of each receiver. Four editions have been printed.

2. "Shortwave Receivers Past & Present - Communications Receivers 1942-1997"  by Fred Osterman - Excellent reference book on later communications receivers. Includes many foreign makes. Circuit descriptions, photos, prices.

3. "Los Angeles Radio Manufacturing - The First Twenty Years" by Floyd Paul - Details the history of Gilfillan Bros., Inc and their licensing relationship with RCA. Many smaller LA companies are also covered.

4. QST, Radio News and Shortwave Craft magazines from 1928 up to 1948 - These vintage magazines are excellent sources for contemporary reviews of equipment and pre-production articles by the designers. Advertisments are invaluable for dating and development of the model line.

5. Operator's Instructions, Factory Manuals, Rider's Troubleshooting Manuals - Original manuals are excellent sources for circuit descriptions, design intentions and performance expectations. Many times the same information is included in the appropriate Rider's Troubleshooting Manual.


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Website Navigation Index

-  WHRM History  ~  Nevada Radio History  ~  The KOWL XMTR  ~  Full Length Articles with Photos -


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

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

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

Parish House History
1876 to Present
Virginia City, Nevada

Lots of Photos


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

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

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

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


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

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



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

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

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

Hallicrafters SX-28
"A Pre-war Masterpiece"

Comprehensive History, Serial Number Analysis, Restoration Details & More

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

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

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

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

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

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

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


-  Rebuilding Communications Equipment  ~  Full Length Articles with Photos -

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

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

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

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

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

 Detailed Information with Lots of Photos

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

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

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

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


- WHRM Radio Photo Galleries with Text -

Entertainment Radios from 1922 to 1950

Roaring 20s Radios
1922 to 1929

Vintage Table Radios
1930 to 1950

Floor Model Radios (Consoles)
1929 to 1939

Only Zenith Radios
1930 to 1940

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

 Early Ham & Commercial Wireless Gear
1909 to 1927

Classic Pre-WWII Ham Gear
1928 to 1941

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

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

Post-WWII Ham Gear
1946 to 1959

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

Vintage Microphones
1930 to 1950s

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

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

Vintage Test Equipment
1900 to 1970

Includes Tube Testers, Freq Meters, Wobulators and More


Radio Boulevard
Western Historic Radio Museum

 Vintage Radio Communication Equipment Rebuilding & Restoration Articles,

 Vintage Radio History and WHRM Radio Photo Galleries

1909 - 1959



This website created and maintained by: Henry Rogers - Radio Boulevard, Western Historic Radio Museum © 1997/2017