Radio Boulevard
Western Historic Radio Museum


Wireless Era Ham Gear

Commercial Wireless Equipment

Early Vacuum Tube Ham Gear

Early Vacuum Tube Commercial Gear


1909 - 1925


photo: Ham Station 6CDG. The homebrew receiver is located center (below the calendar.) The receiver output goes to the Western Electric 7A (three 216A tubes) audio amplifier (left of the receiver) and it drives the Western Electric 10-D horn speaker. The rig to the far left is a small transmitter (note the mike and key in front of the rig.)  The homebrew transmitter to the right has two WE 211 tubes protruding out of the top. Also note the key and mike in front of this transmitter. Magnification of this high quality photo revealed that the calendar is turned to April 1923.   From 6CDG's "Real Photo" PC-QSL.

Wireless Era Ham Gear & Commercial Wireless Equipment

M. H. Dodd  -  1909 Wireless Receiver

Most people don't even recognize this item as a wireless receiver because it is so primitive but the vintage photograph above shows M.H.Dodd at the controls of his prize-winning 1909 wireless station and the receiver is very obvious setting on the smaller table to the left. Documentation on Dodd's 1909 station is provided by that fact that Dodd entered his station (actually, a photograph of his station) into a Wireless Station Contest that was held each month by Modern Electrics magazine. Dodd's station won First Prize and was featured in the June 1909 issue of Modern Electrics. The photograph used in the magazine is the same photo shown above except that the photo above is a scan of the original print and is not a copy of the magazine printed photo (the original print does have that over-exposed look at the right side - so does the photo in Modern Electrics.) There is a link provided to the 1909 ME Wireless Contest article (from Google Books) in the "M.H.Dodd's 1912 Wireless Station" web-article. Navigation link at bottom of this page.

The Tuning Inductance and Detector Stand are homebrew. Dodd wound his inductance on a form that was made from a 3" diameter 24" long piece of Bamboo - something you don't run into very often. The slider uses a spring-loaded ball contact against the windings. The single earphone headset is from the Kellogg Company and Dodd has this headset on in the 1909 photo. Also visible in the 1909 photo is a bias adjusting resistance, probably for an Electrolytic detector, a detector switch, a glass cylinder, a telephone microphone and another earphone. Bias batteries can be seen below the table. The transmitter uses two spark coils, a homemade condenser made from glass photo plates and a homemade helix. The transmitter is probably using lead acid batteries that are not quite visible below the small "receiver" table. Most of the 1909 Station parts seen in the photo were used to construct Dodd's 1912 station (next-below.) 



1912 Wireless Station


This is the Wireless Station that M.H.Dodd built in 1912. It is a "pre-regulations" ham station that is virtually complete, authentically reassembled and is displayed with photographs, taken in 1912, showing Dodd using his station. Dodd's station survived intact because the new regulations (the 1912 Radio Act (Alexander Bill) that went into affect in December 14, 1912) made both Dodd and his station illegal. Rather than rebuild the equipment (for 200 meter operation) and get the new license required, Dodd disassembled the station in 1913 and packed it away in a large trunk. The station remained in that trunk for the next 86 years until I discovered it in Dodd's backyard shed at his home in Reno, Nevada. For the complete story on this amazing find, with lots of photos, go to the navigation link below and click on "M.H. Dodd's 1912 Wireless Station."




Wm. J. Murdock Co.  -  No. 334 Receiving Transformer  aka: Loose Coupler

These "Receiving Transformers" were generally called "Loose Couplers" and they were used as the receiver's tuned circuit in many early stations. Before 1915, most receivers and transmitters consisted of the various components placed (or mounted) on a table with inter-connecting wires to form the circuitry needed. Since experimenting was an essential requirement for the amateur operators of the day, the ability to try various "hook-ups"  was aided by these "easy to modify" station components. The receiver's Loose Coupler provided the user with the ability to crudely tune in signals and to somewhat control the selectivity of his receiver. The larger coil is the Primary Inductance and the antenna and ground are connected to this coil. The slider roughly tunes the antenna to resonance for whatever frequency it is desired to receive by reducing the number of turns in the primary and, depending on the connections, may short the "dead turns" to ground. The smaller coil is the Secondary Inductance and this coil is tapped at various numbers of turns that are brought out to the contact point switch. The contact point switch roughly tunes the secondary to the frequency that is to be received by reducing the number of turns on the secondary coil and depending on how it's connected may also short out the "dead turns" to the coil return or to ground. By sliding the Secondary into the Primary, tighter coupling is achieved resulting in stronger signals but with broader bandwidth. By withdrawing the Secondary, looser coupling is achieved and greater selectivity is accomplished but at the expense of signal strength. However, the proximity of the Secondary Coil to the Primary Coil will vary the mutual capacitance so the desired "tuned" capacitance and frequency resonance changes somewhat if the coupling position is moved. Changing the taps on the secondary inductance and sliding the primary inductance adjustment allowed "rough" tuning of a received signal while maintaining the same coupling position. More elaborate set-ups would add variable condensers to provide easily adjustable tuning to resonance of the Primary and Secondary Inductors while allowing the coupling to remain set in position. To create a receiver, a mineral detector was added in series with the secondary to the 'phones. The addition of a small telephone condenser, which was generally connected across the 'phones, would filter out the RF and provide better (and slightly louder) audio response.

William J. Murdock Company started in business in 1896 building various kinds of electrical equipment for telephone and telegraph service. Wireless equipment was added to the line as knowledge and interest about sending and receiving wireless signals became popular. The No.334 dates from 1913 or 1914 (up to 1917) and its original selling price was about $15.00.


Wm. J. Murdock Co.

Receiving Transformer - Loose Coupler


In December 1912, new wireless regulations moved amateur operation to a region of the spectrum then thought to be useless, "200 meters and below" or everything above 1500kc. There were amateurs that had been using these higher frequencies before the 1912 Radio Act but they were few in number. The Murdock Loose Coupler shown is certainly for the higher frequencies judging by its small size. Note that the slider bar has two connections that would appear to be a short circuit however the binding post nearest the secondary coil is actually insulated from the slider bar with fiber washers and has the end of the primary coil wire soldered to the screw head. This post serves as the antenna connection while the post on the opposite end of the slider bar is ground. The primary is wound onto a "cup" like form made out of hard rubber that has machined grooves for the coil wire. The vertical arrangement for the secondary coil guides is unusual. The eyelets installed in each corner of the base provided screw-marring protection when the Loose Coupler was mounted to a table. The base is poplar wood stained reddish-brown to look like mahogany. As yet, a model number for this Murdock can't be found (or an original selling price) but it likely dates from about 1913 or 1914 up to as late as 1917.


The Radio Apparatus Company

"TRACO" 5A - Navy-Type Receiving Transformer - Loose Coupler

Navy-type loose couplers will have the primary inductor enclosed or partially enclosed in a box with a front panel mounted to the box and tapped switches for adjusting the number of turns on the primary coil. Some Navy-type couplers will have an "on-off" switch (as the 5A does) that disconnects the antenna from the primary. The front panel will also have terminals for connecting the antenna and ground along with two terminals for the secondary inductor. The secondary will generally have an adjustment of the number of turns of the coil with a switch that is mounted so it can be accessed without reaching around to the front of the secondary.

"TRACO" was a trade-name for The Radio Apparatus COmpany products. They were located in Pottsdam, Pennsylvania. The 5A sold for about $18 around 1917. The 5A was also sold through Sears-Roebuck.

The front panel is hard rubber which, when exposed to bright light for years, will turn brown. The inside of this panel is black but the outside has "aged" to a greenish-brown color. The wood is poplar that is finished in the typical dark red mahogany color of the time. The upper two terminals on the front panel connect to the secondary coil. The two lower terminals are antenna (left) and ground (right) connections. The outer semi-circular contacts adjust single turns on the primary while the inner set of contacts adjusts tens of turns.


Signal Electric Co.

R-22 - "Arlington" Loose Coupler

The larger Loose Couplers were sometimes called "Arlington" types since they could tune to the very long wavelengths for time signal reception (the Time Signal station was located in Arlington, VA and operated at VLF frequencies.) Arlington-type Loose Couplers will have a greater number of turns on the primary and secondary with larger coil dimensions. The Loose Coupler shown is not marked but appears identical the Signal R-22 from about 1914-1917. However, Signal Electric usually stamped "SIGNAL" into the top of the smaller front wood block that supports the secondary coil support rods. It's also possible that this Loose Coupler might have been from Wm. Duck Co., as those types are also identical to the one shown in the photo.

Loose Coupler Receivers using mineral detectors will only respond to amplitude modulated signals. During the "wireless era" nearly all signals were from "spark" transmitters that were actually called "damped wave" transmitters that used various types of interrupters. e.g., buzzers, electrolytic interrupters or rotary interrupters. The signals from these transmitters were essentially a keyed modulated carrier wave and could be demodulated by the crystal/mineral detector and become audible in the 'phones. Likewise, "radiophone" signals were voice amplitude modulated carrier wave signals that could also be demodulated by the detector and become audible in the 'phones. By the early 1920s, vacuum tube continuous wave (CW) transmitters were becoming popular. Also, the Navy was using arc transmitters or Alexanderson Alternators that are also CW transmitters. These of types of signals can't be demodulated properly using just a mineral detector (other than maybe hearing the carrier turn on and off with very strong signals.) The era of the Loose Coupler receiver ended for hams and other CW users in the early twenties as vacuum tube receivers using regenerative detectors became popular. 



Chelsea Radio Co.

Wm. J. Murdock Co.

These variable condensers were generally used with Loose Couplers to provide more accurate tuning of the primary and secondary inductances in amateur wireless receivers. These two happen to have plastic covers but some earlier versions have the entire housing cast out of hard rubber or bakelite. The Murdock is from about 1915 and the Chelsea is from about 1920.

When initially used with a loose coupler, only the primary (antenna) was tuned. It was thought at the time that accurate tuning of the antenna circuit resulted in the best transfer of energy to the secondary circuit, which then only needed to be roughly tuned using a tapped switch to select the number of secondary turns that resulted in the best signal. Later receiver set-ups added another variable condenser to accurately tune the secondary to resonate with the primary for the best transfer of energy and the best reception of signals.



1/2 KW Wireless Transformer, Type R

These high voltage transformers were the "heart" of many amateur spark stations providing the necessary potential to charge sending condensers and create the damped waves which were the main component of spark signals. The primary of the transformer is keyed via the AC line with perhaps a primary choke also in the circuit for extra protection. The secondary is connected (usually through kickback preventers) to the closed circuit (usually an oscillation transformer primary, charging condenser and rotary spark gap.) The closed circuit is coupled to the antenna via the oscillation transformer secondary. On a 1/2KW transformer the secondary voltage is about 12KV. The levers control a sliding section of the core that can be moved in or out, creating an adjustable "magnetic leakage gap" which served several purposes. Initially, it allows some control over the power output of the spark transmitter but it also serves to limit the high primary current that flowed during the discharge at the spark gap (this discharge was a momentary short on the secondary) and also to help prevent transmission at two frequencies (called double wave emission - this can also be a product of excessive coupling in the oscillation transformer.) The Type R sold for $21 in 1917, just before the WWI Navy ban on receiving and transmitting. This ban was not lifted until April 1919 for receiving and October 1919 for transmitting.



J.H. Bunnell Co.

Mascot Spark Gap


An early spark gap from Bunnell advertised in Modern Electrics and Mechanics in 1914. It is mounted on a ceramic base and the tips are made of zinc. Zinc was supposed to produce a very clear "spark tone" - certainly a relative statement of the "spark days." Selling price in 1914 was $1.00 The one knob on the left is not original.

These "stationary gaps" were used in spark transmitters where the source of the charging voltage was a "spark coil." Spark coils could provide a higher frequency charging rate to the sending condenser-spark gap-helix (closed circuit) resulting in fairly good dampening. It was also possible to use electro-chemical interrupters along with a high voltage transformer, however, most transformer operated stations used rotary gaps, like those shown next.


klitzen.jpg (21739 bytes)

Klitzen Radio Mfg.

Rotary Spark Gap No.125

Micaoil 1KW Condenser

This Klitzen No.125 Rotary Gap is from 1920 and originally sold for $22. The Klitzen Micaoil Sending Condenser is .01uf at 30KV rated at 1KW and is also from around 1920. The condenser uses mica as a dielectric and oil for insulation along with cooling. These components would have been used (along with an oscillation transformer) in a transformer-energized spark transmitter to provide the spark gap and the capacitance necessary for damped wave signal generation.  Using a rotary gap in the secondary circuit gave the advantage of audio frequency modulation. This was accomplished by allowing the gap discharge to occur at various random levels of the charging AC voltage (non-synchronous rotary gap.) The varying discharge voltage and resultant different amplitude peak of the damped waves in each wave train was heard as an audible tone allowing better copy. The approximate audio frequency can be calculated by dividing the motor RPM by 60 and multiplying by the number of discharge contacts, 12 in the case of the Klitzen 125. The Hamilton-Beach motor was specified at up to 4000 RPM so the frequency would be around 800Hz at maximum RPM. Apparently other parts houses offered the Klitzen under their own name since there are no tags or embossing to provide a way to identify the actual manufacturer. Franklin was one such parts house that offered the Klitzen No.125 as the "Franklin Rotary Spark Gap." at the astounding price of $40.


Commercial-Homebrew Rotary Spark Gap


Many wireless parts houses offered various components to built your own equipment, called "homebrewing." Shown in the photo to the left is a rotary spark gap that is most likely commercial but could also be a combination of commercial wheel, bearing and dual adjustable stationary contacts and a homebrew oak base. Actually, the oak base looks too good to be amateur construction but some of the incredibly talented hams of that time were certainly capable of building the entire apparatus. The insulated pieces are made out of hard rubber and the metal parts are nickel-plated brass, which seems to imply a commercial source for these parts. It appears that this rotary gap was probably belt-driven. It might be possible that the belt drove the shaft directly, or, more likely the sheave (pulley) has been removed from the shaft. There are no indications that a motor was mounted to the oak base, therefore some other means was used to drive the disk. To produce a suitable "tone" this rotary gap would have to turn at a very high RPM since all of the contacts on the wheel are commonly connected and the dual stationary gaps would have been connected in series thus given six "breaks per revolution." Around 6000 RPM would give a 600Hz tone.



3ON  Amateur Station Parts


In 1923, John Ridgway was licensed as 3ON. He was only 11 at the time but he was able to construct quite a nice Loose Coupler using the oak boards from a discarded bed frame. The spark coil is a 1" Commercial and the sending condenser is homebrew using glass and foil. Spark was certainly on the way out by 1923 but John was able to make a few contacts and hone his ham skills. John became SK in January 2006 at the age of 93.



Peerless Wireless Company

"High Grade Radio Apparatus"

Model B

Peerless Wireless Company was located in Detroit, Michigan and offered this assembled "Model B" receiver using a Loose Coupler tuner with crystal detector as their "High Grade Radio Apparatus." The original detector was replaced with a later, after-market Galena detector that was probably of better quality (and more sensitive) than the original. Two sets of earphones can be used with this set - the two sets of "TEL" terminals are connected in parallel. The large contact switch tunes the primary coil by selecting the number of turns. The secondary turns are selected by the contact switch on the front of the secondary coil form. The small switch allows the antenna to be removed from the primary coil - an early form of  "send -receive" switch. A fixed condenser is located under the board. Dates from around 1914 to 1917.



Early Vacuum Tube Receivers

Spherical Audion Receiver - 1915

The builder of this wonderful Spherical Audion Receiver is unknown. Dating the Audion Receiver to 1915 was arrived at by noting that the circuit is non-regenerative - regeneration became popular around 1916. Also, "dead-turns" (unused sections of tapped inductors) are not grounded - this was commonly done by 1917. Additionally, the spherical audions were being replaced by tubular audiotrons around 1916. The approximate date of 1915 seems likely for this receiver. The circuit uses a Loose Coupler tuner and a non-regenerative, grid-leak detector. On the lower right side of the panel is a dual control the outer knob of which varies the coupling via a bell crank while the inner knob selects the secondary turns. Another clever control is the large antenna tuning series condenser - if it is rotated to either end of its scale and the metal pointer put into contact with the stop pins, the condenser is then shorted and essentially taken out of the circuit. The back-up crystal detector appears to have been a somewhat later addition since the quality of workmanship doesn't match that of the original construction (although that later date is probably still before 1917.) A crystal detector was a common addition to early audion detectors as it allowed the receiver to still be used if batteries were depleted or the audion failed. The cabinet is mahogany and the panel is .75" thick hard rubber. Signals picked up on this receiver are either weak or inaudible! Regeneration would have been a big help but even the commercial regen sets were at least a year away, (1916 Paragon RA-6.) This working receiver was tested using several different kinds of detector tubes by way of a homemade adaptor. The best performance was using a Moorhead ER type tube, though these are vintage 1919 tubes. The sensitivity was a bit better than a modern germanium diode (but not by much.)


Navy Type SE-1420 - Wireless Specialty Apparatus Co.

This is the "Navy Destroyer" receiver designed by Louis Hazeltine at the end of WWI. Hazeltine was a Stevens Institute graduate and then subsequently became an instructor there. The design request came from a former Hazeltine student who was now in charge of receiver development at the Washington Navy Shipyard. The Navy wanted a receiver that was capable of operation in the presence of nearby spark and arc transmitters. Hazeltine achieved this selectivity by using a sophisticated Antenna Tuner that was completely shielded and only coupled to the Secondary Tuner by a small variable coupling coil. The first Navy contracts were built by either AMRAD or Wireless Specialty Apparatus. The circuit uses a single vacuum tube (either a VT-1 or Moorhead ER) as a three-circuit tuner with a regenerative/autodyne detector. Wavelengths covered were from 300 meters to about 7500 meters. The entire cabinet is lined inside with copper sheet with an additional copper shield to provide complete isolation between the Antenna Tuner section and the Secondary Tuner circuit resulting in great selectivity and immunity to interference. This complete shielding also eliminated stray pickup. SE-1420 type receivers were built by various contractors though most of the 1920s. The Coast Guard version, CGR-5A (SE-1420C) was contacted in June, 1927. The U.S. Army Signal Corps designated the later SE-1420 versions as the BC-131. There were several variations and upgrades to the receivers, some with different frequency coverage but the same basic style is easily recognized. The various end users were the Navy, the Army and the Coast Guard.

Wireless Specialty Apparatus was organized in 1907 by Greenleaf Pickard and John Firth. United Fruit Company purchased WSA in 1911. In 1920, United Fruit became part of the cross-licensing arrangement headed by GE (and included RCA, AT&T and Westinghouse) because UF/WSA owned all crystal detector patents (because of Pickard.) Around the same time, WSA started to provide a commercial version of the SE-1420 designated as the IP-501. The Triode Type B, Two-Stage Audio Amplifier was also offered with the IP-501 along with a Long Wave Adaptor to allow tuning into the VLF range. Probably because of the cross-licensing, these WSA receivers and associated equipment were sold by RCA until 1923, when WSA was purchased by RCA. From 1923 to 1927, RCA continued to sell marine radios built exclusively for them by WSA. In 1927, RCA combined WSA with another purchased company, Independent Wireless Company, and created Radiomarine Corporation of America which operated as a subsidiary of RCA. RMCA continued to build and sell the IP-501 and IP-501A into the early 1930s.

The SE-1420 shown above is an early type from a 1919 or 1920 contract built by WSA. I've owned this SE-1420 since 1990 but the restoration had remained unfinished due lack of detailed photos of  what the missing complex tube socket looked like. In 2009, armed with new detailed information, I replicated the socket and completed the SE-1420 restoration. Although the restoration used several replica and non-original parts, authentic vintage material and techniques were utilized in the rebuilding of the receiver. The SE-1420 is a great performer and has received airport NDBs from all over North America. More details on the restoration and performance in our web article.

For the ultimate information source on the SE-1420, IP-501 and IP-501A wireless receivers that includes history, construction, restoration and operation of these marvelous receivers and also includes "Tuning in NDBs with the IP-501-A" see "WSA & RMCA - SE-1420, IP-501 & IP-501-A - The Classic Shipboard Wireless Receivers"  in the navigation index below.


Navy Department - Bureau of Engineering

NESCO - National Electrical Supply Company

SE-1387 R.F. Driver  &  SE-1834 Universal Amplifier

The SE-143 was a WWI Receiver that was essentially a RF Tuner. It was used extensively by the Navy and other versions, like the IP-500, were used by commercial users. The SE-143 didn't have an onboard detector or audio amplifier. These components were externally added to the SE-143 installation for a complete receiver. During WWI, the detector was usually a mineral-type that might provide multiple types of detector minerals. The SE-143 could also operate with an external regenerative detector tube and the receiver provides a "Tickler" coil (variable inductance) connection for that function. The audio amplifier of the time was usually a single stage circuit using an Moorhead ER or a WECO VT-1 triode tube. As radio evolved post-WWI, RF amplifiers used ahead of a regenerative detector provided stronger signals and increased isolation of the oscillating detector from the antenna. By 1922, several types of devices were available to improve the older receivers, specifically the SE-143.

The SE-1387 is a R.F. Driver that tunes from 125M to 30,000M. It uses a single WECO 215A tube RF amplifier that's designed to take the "tuned" LC that the SE-143 provided and use that as the "tuned" input signal (marked RECEIVER) to the TRF stage of the SE-1387. Since the SE-143 didn't have an onboard detector, the output of the SE-1387 is coupled to the input of the SE-1834, an "Amplifier - Audio Universal." The SE-1834 uses six WECO 215-A tubes. The input is from a variable "coupler" coil in the SE-1387 to a detector tube in the SE-1834. The detector input is roughly tuned by selecting the proper frequency within the 125M to 30,000M range. The SE-143 Tickler connection is connected to the Tickler terminals of the SE-1834  with the link removed. This would have SE-143 operating with one stage of TRF amplification, a regenerative detector and five stages of audio amplification. For receivers that didn't provide a Tickler coil, the link was left connected and the detector operated as a "non-regenerative" detector. The switch selecting "Radio Audio" and "Audio Grid" determines if the first stage acts as a detector (RF) or if it acts as an audio amplifier (audio grid.) Generally, the SE-1387 and SE-1834 combination was specifically for use with the SE-143 but other many other types of receivers and combinations could accommodated using the switches and links provided.

NESCO was the National Electrical Supply Company. They were located in Washington D.C. and began operating in the late-1890s. They were very involved with early Navy equipment. Reginald Fessenden also had a company called NESCO that was the National Electrical Signaling Company but it was out of business before WWI started. NESCO changed their name in the late-thirties to National Electrical Machine Shops then using the acronym NEMS. In the 1950s, NEMS worked with Alan Clark building NEMS-CLARK VHF receivers. 


Adams-Morgan Co.

 "Paragon" RA-10/DA-2 Receiver

The Paragon was designed by the quintessential ham and radio engineer, Paul Godley. A favorite of the "Spark Hounds," the Paragon RA-10 tuner was first offered in 1920. Later, in 1922, the DA-2 detector and two-stage audio amplifier became available. Paul Godley had designed the RA-6 - the first commercially built shortwave regenerative receiver - prior to WWI. After the war, Adams-Morgan and Chicago Radio Labs still offered the RA-6 for awhile. Godley redesigned the tuner using an air variable condenser in the secondary circuit and a variometer in the plate circuit for regeneration control. This became the RA-10. The new Paragon was Godley's choice as one of the receivers taken to Ardrossen, Scotland for the Amateur Transatlantic Tests, in December 1921. Though most of the stations were actually received on Godley's homebrew superheterodyne receiver, he did have a RA-10 and a proto-type DA-2 set-up on the receiving table in the tent at Ardrossen. Adams-Morgan took full advantage of the advertising potential of the Tests claiming the Paragon had received all of the ham stations. It didn't matter since the RA-10/DA-2 were very good performers and probably could have received much of what was claimed. Upon his return to the USA, Godley made an off-hand comment about the 50 watt vacuum tube oscillators out-performing the 1KW spark stations that probably put the death-knell to spark transmitters, at least as far as the hams were concerned.


Standard Assembling Company

The Standard Assembling Company offered this regenerative tuner utilizing a Deforest tuner and Duo-lateral Coils for $50 in 1921. It was also available in kit form for $45. Using a DeForest type tuner can be very annoying because the location of the adjusting knobs requires the operator to reach over the coils. The hand capacity involved in making adjustments de-tunes the receiver resulting in temporary settings that change soon as the hand is removed. Most operators would use a pencil to push the coils into the proper adjustment instead.


Sydney J. Fass

3-tube Regenerative Receiver

Sydney J. Fass had been a commercial sea-going and maritime shore radio operator since 1909. He was active in San Francisco's early radio amateur community. Fass started a radio business, probably selling and servicing radios, that was located within San Francisco's famous "The White House" - a large department store located on Grant and Sutter in San Francisco. Fass' radio business had a long history as "the longest, continuously operating radio business in San Francisco." The White House closed in 1965.

The homebrew radio shown is a three-circuit tuner using three tubes that was built by Syndey Fass in the early twenties. The variometers and the audio interstage transformers appear to be from around 1921 and are probably built by Remler. The audio interstage transformers are also very early twenties vintage from an unknown builder and labeled as "Amplifying Transformer." A Lemco grid leak condenser is used (Lemco was Lee Electric & Manufacturing Company in San Francisco, famous for their crystal sets.) The variocoupler is unlabeled but appears to be from the early twenties. The filament controls are for one amp tubes. The cabinet lid, part of the bottom and the entire panel are lined with tin foil that is connected to the ground terminal for the shielding necessary for reducing hand-capacitance effect that is most prevalent when the detector is oscillating. This oscillating condition implies that the receiver was to be used as a ham receiver for reception of CW. By the early twenties, spark transmitters were rapidly being replaced by tube oscillator transmitters. The tube transmitters sent CW signals (spark transmitters sent damped wave signals - similar to MCW - which didn't require the detector to be oscillating.) Shielding of the control panel and the top lid would have allowed this receiver to operate in an oscillating condition without too much instability. Although by the mid-twenties a regenerative receiver without any isolation between the antenna and the detector was considered obsolete for broadcast reception, hams and commercial shipboard users continued operating regenerative receivers throughout the twenties.

Typical of many homebrew ham receivers of the day, the cabinet on the Fass receiver is quite long - 31 inches long. Someone in the past installed an engraved plastic plaque under the lid that says the following: "Radio Receiver - built in 1921 by Sydney J. Fass from parts made by Remler Company, the West's pioneer electronic manufacturer. This receiver was the start of a successful radio business at The White House, San Francisco, oldest continuous radio dealer in the Bay Area."  As to whether this receiver is Fass' ham receiver or a homebrew broadcast receiver, most homebrew ham receivers could double as a broadcast receiver.


A.H.Grebe - CR-5,  CR-9  and  Single-Circuit Tuners

A Single-Circuit Tuner uses a direct connection to the antenna with only one tuned circuit to select frequency. Three-Circuit Tuners use a Primary Tuner for the antenna, a variable coupling coil and the Secondary Tuner. Single-circuit tuners are simple to operate but don't provide much selectivity. Three-circuit tuners are difficult to operate correctly but can provide excellent sensitivity and selectivity.

The Grebe CR-5 is an Intermediate Wave, single-circuit tuner with a regenerative detector that uses a UV-200 soft detector tube. The CR-5 tunes from 3000 meters down to 150 meters, or, 100kc up to 2000kc. The amateur that bought the CR-5 could up-grade his receiver, (when he could afford to), by purchasing the two-stage audio amp, RORK, and later add an RF amplifier, RORN, or other accessories that Grebe offered. The CR-5 sold for $80 in 1921.

The CR-9 is also a single-circuit tuner with regenerative detector but also included in the circuit is a two-stage audio amplifier. This allowed the purchaser to have a complete receiver that was able to drive a loudspeaker. The CR-9 is shown below.

Grebe CR-5 from 1921

Since basically the same tuner as the CR-5 is used in the CR-9 providing tuning from 100kc up to 2000kc, the CR-9 was a decent, useable Broadcast receiver in 1921. Regulations had all BC stations on 360 meters or 400 meters, so the CR-9 could successfully receive these types of stations. Grebe did market the CR-9 as a BC receiver for a while and sold thousands of them. 

Since a pure-tungsten filament, argon gas filled detector tube is used in the Grebe CR receivers, when setting up the receivers, a method of adjusting the detector plate voltage will be advantageous. In the early twenties, a plate potentiometer was used that allowed varying the detector voltage by about six volts (the potential of the A battery usually.) By using the +18vdc tap on the detector battery one could adjust the plate voltage from +18vdc to +24vdc. There is interaction between the filament voltage, the detector plate voltage and the regeneration control, so having the plate voltage adjustable generally means you can set the detector filament voltage and leave it alone. Only the plate voltage (which doesn't have to be adjusted much either) and the regeneration will require some adjustment depending on the frequency being tuned.

To achieve maximum selectivity with a single-circuit tuner, the regeneration must be just before or just after the oscillation point. For AM voice transmissions, just before oscillation will provide best sensitivity and best selectivity.  For CW, just after the oscillation point also provides best performance. One will note that if the regeneration is not at the oscillation point (either before or after oscillation) several signals will be received simultaneously since there won't be much selectivity. One also had to be aware that, if the detector was oscillating and there wasn't any isolation between the detector and the antenna, a carrier wave would be transmitted by the receiver at its tuned frequency. Simple regenerative detectors that were misadjusted by neophyte radio enthusiasts caused many of the cases of neighborhood radio interference in the early twenties.      >>>

>>> Since single-circuit tuners were not all that selective, even at the oscillation point, most radio operators preferred the three-circuit tuner with a primary tuner, coupler/secondary tuner and a regeneration tuner. However, the single-circuit tuner of the CR-5 or CR-9 could be operated with a separate RF amplifier, such as the Grebe RORN, to improve both selectivity and sensitivity.


Kennedy - Type 220 - Intermediate Wave Receiver

Kennedy receivers were the favorites of experimenters, radio enthusiasts and some hams. There were some commercial users, especially early broadcast stations where the receivers were used as emergency frequency monitors required by early regulations. Kennedy receivers were built to a high quality standard which meant a high selling price. The Kennedy Type 220 Intermediate Wave Receiver and matching Type 525 Two-Stage Audio Amplifier made a very nice combination for either commercial use or for a well-to-do radio fan. It tunes from 3000 meters to about 150 meters, or about 100kc up to 2000kc, using a three-circuit tuner operating a regenerative detector. Early versions will have a Plate Potentiometer adjustment for controlling the plate voltage on the detector tube. The standard detector tube used was a soft-detector, the UV-200. The amplifier used hard-amplifier tubes, the UV-201. Kennedy receivers are usually described by the location of manufacture which was a chronological event and resulted in slightly different construction of the receivers. Early Kennedy receivers built in San Francisco will have nickel plated binding posts and plate potentiometers while later St. Louis versions have bakelite capped binding posts and no plate potentiometer. There are many other variations between the two versions and almost any example will differ from another in some small detail. This was due to the way that Kennedy equipment was built - all hand made. Though machines were used to make the various parts, since the machines were operated by hand, the resulting parts do have variations. Top quality was apparent with the silver plated dials on Formica panels that were machine engraved, all housed in a solid walnut cabinet. The 220/525 combination was introduced in 1921 and sold for over $200. In June of 1922, Kennedy was purchased by Wagner Electric and the operation was moved to St. Louis, Missouri.

For the ultimate information source on the 1922 Kennedy Receivers and Audio Amplifiers, includes Colin B. Kennedy history and history of each receiver, operation of the equipment, restoration suggestions, correct schematics and interior photos of the equipment plus an article on Dr. Royal Rife's use of Kennedy equipment in his laboratory, see "Colin B. Kennedy - "Radio Apparatus of Quality" in the navigation index below.


Colin B. Kennedy Co. - Type 281 - Shortwave Receiver

Colin B. Kennedy was usually a builder of high quality home radios but if you were an affluent ham or experimenter, you might want to buy a Type 281 shortwave receiver with its matching Type 521 Two-Stage Audio Amplifier for your station. Using a standard Armstrong three circuit regenerative tuner, the 281 tunes from about 600 meters to about 150 meters, or about 400kc up to 2000kc. Most amateur operation in the early twenties was on 200 meters (1500kc and up.) The set uses a soft-detector (UV-200) and the amp uses two hard-amplifiers (UV-201) tubes. A solid mahogany cabinet and polished Formica panel are indicative of the quality and care that went into the building of Kennedy receivers. Introduced in 1921 and sold for $145.

For the ultimate information source on the 1922 Kennedy Receivers and Audio Amplifiers, includes Colin B. Kennedy history and history of each receiver, operation of the equipment, restoration suggestions, correct schematics and interior photos of the equipment plus an article on Dr. Royal Rife's use of Kennedy equipment in his laboratory, see "Colin B. Kennedy - "Radio Apparatus of Quality" in the navigation index below.


Kennedy - Type 110 - Universal Receiver

The ultimate in quality and performance for the experimenter or radio enthusiast. The Kennedy Universal was so well-respected that it was still being sold in 1925 when most regenerative receivers were considered obsolete. Since the ad was in the April 1925 issue of QST, Kennedy probably believed that only the hams would be interested in a large regenerative receiver by that time. The Universal tunes from 25,000 meters to 150 meters (12kc up to 2.0mc,) which was just about everything you would listen to back in 1921, when it was introduced. A three circuit tuner operates the regenerative detector and a variometer controls the regeneration. Priced at over $300, it was certainly for the well-to-do. Kennedy 110 receivers were found in many early broadcast stations as emergency frequency (500kc) monitors. The 110 shown is SN 951 and the 525 is SN 644, both very early three digit numbers in the typical Kennedy-San Francisco style with nickel plated binding posts and the Plate Potentiometer adjustment. Performance on this functional example is first-rate and, in the 1980s, I won first place (regenerative receivers) in Radio Age's "Radio Receiving Contest" with this Kennedy 110/525 combination.

One electro-mechanical necessity not found in any of the 1922 Kennedy receivers is any type of shielding. No panel shield or cabinet shields were installed on any of the Kennedy line of receivers. These were three-circuit regenerative detector receivers that could be used by professional radio operators to receive CW signals and that would require an oscillating detector to demodulate correctly. When oscillating, the receiver's various controls all have EM fields associated with those controls. This results in severe "hand capacitance effect" when trying to tune or adjust the receiver. Most regenerative detector receivers installed panel shielding or control shielding to prevent "hand capacitance effects." Why a "high-end" receiver like the Kennedy line never installed any shielding is a mystery. Perhaps Kennedy believed their receivers would only be used for radiophone reception or for damped-wave (spark) transmissions. However, vacuum tube CW transmitters were becoming very popular in the early twenties and the Navy was using arc transmitters or Alexanderson alternators that also sent CW signals that required an oscillating detector for proper demodulation. The "hand capacitance effect" can be compensated for by tuning very slightly lower in frequency than the desired signal's frequency. When the hand is removed from the control, the received frequency will jump up slightly,...hopefully to the proper signal frequency (it takes a little practice but it does work.)

For the ultimate information source on the 1922 Kennedy Receivers and Audio Amplifiers, includes Colin B. Kennedy history and history of each receiver, operation of the equipment, restoration suggestions, correct schematics and interior photos of the equipment plus an article on Dr. Royal Rife's use of Kennedy equipment in his laboratory, see "Colin B. Kennedy - "Radio Apparatus of Quality" in the navigation index below.


Wireless Specialty Apparatus Co. - RCA Radiomarine Corporation of America

IP-501-A  Receiver-Amplifier

The IP-501-A was the classic shipboard wireless receiver. Its incredible performance, robust construction and high reliability made it the "standard" for all maritime receivers that followed. It was developed from the Navy SE-1420 and later IP-501 series of wireless receivers. A three-circuit regenerative/autodyne detector is combined with a two-stage audio amplifier along with all the extra features that would be required for reliable communications at sea. Wavelength coverage is from 300 meters up to 7500 meters (1000kc down to 40kc, though most receivers tune from 1200kc down to 37.5kc.) The oak cabinet is lined with copper sheet and and an extra copper shield isolates the Antenna Tuner from the Secondary Tuner for top-notch selectivity. Construction is heavy-duty, quality is first-rate and the performance is incredible. All screw and nut joints are soldered after tightening at assembly. This was to prevent anything from coming loose inside the receiver with the constant vibration encountered onboard ships at sea. The solder also protected the screw threads from corrosion.

The earliest versions of the IP-501 family were built by Wireless Specialty Apparatus. However, many SE-1420 receivers were built under contract by AMRAD and by NESCO. From 1920 until 1923, all WSA IP-501 type receivers were sold by RCA since Wireless Specialty Apparatus, a company owned by United Fruit Company, was cross-licensed with the RCA/GE/Westinghouse Group. In 1923 or 1924, RCA was able to purchase WSA along with their manufacturing plant and began selling the IP-501 series built exclusively for RCA. In 1927, RCA combined WSA with another acquisition, Independent Wireless Company, to create Radiomarine Corporation of America. Radiomarine became a subsidiary of RCA and provided commercial shipboard equipment, operated the RCA coastal stations and handled the RCA Radiogram service.

The IP-501-A receivers (and their variations) continued to be built up into the late-twenties, perhaps even later. Manuals were available as late as 1936. Most IP-501-A receivers were removed from ships just prior to and during WWII since their regenerative detectors easily coupled into the antenna tuner section and then up to the antenna. An oscillating IP-501-A could be heard easily up to five miles away when operating at sea.

The IP-501-A shown is the early version with Telephone Condenser switch and nickel plated binding posts. Later versions eliminate the TC switch and the binding posts use bakelite caps. This particular receiver was originally used aboard the Matson Line steamship S.S. Mariposa. I have owned this IP-501-A for over 40 years. A ham friend of mine traded a telephone pole for it and then sold it to me. I have performed three restorations on the set over the years, each one more complete and more original than the former one. The final restoration (in 1984) resulted in the receiver looking totally original inside and, of course, fully functional. It is a very sensitive receiver and the calibrated wavelength dial is quite accurate - at least as accurate as you can be using wavelength, that is.

For the ultimate information source on the SE-1420, IP-501 and IP-501A wireless receivers that includes history, construction, restoration and operation of these marvelous receivers and also includes "Tuning in NDBs with the IP-501A" see "WSA & RMCA - SE-1420, IP-501 & IP-501-A - The Classic Shipboard Wireless Receivers"  in the navigation index below.


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