Western Historic Radio Museum

Wireless Era Ham Gear
and
Commercial Wireless Equipment

1910 - 1927

 Photo: "I told you not to move!"  -  Wireless Operator onboard the S.S. Columbia (photographed by M.H.Dodd  -  ca.1913)  Note that all of the equipment and the op's suit is in perfect focus - just his head isn't.

M.H.Dodd  -  1910 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 1910 station and the receiver is very obvious setting on the smaller table to the left. 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 1910 photo. Most of the other 1910 Station parts seen in the photo were used to construct Dodd's 1912 station. 

M.H.Dodd's

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 we 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."

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.

Signal  R-22 - "Arlington" Loose Coupler

These "Receiving Transformers" were generally called "Loose Couplers" and 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 shorting out a portion of the 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 shorting out turns. 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. The Secondary Coil has a certain amount of inherent capacitance and the capacitance also varies somewhat with the coupling, so technically the Loose Coupler can be operated alone with just a detector and 'phones added to complete the receiver. More elaborate set-ups would add variable condensers to tune both the Primary and Secondary Inductors for more precise tuning and a telephone condenser was generally connected across the 'phones to filter out the RF. 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 above is not marked but is almost certainly the Signal R-22 from about 1914.

Wm. J. Murdock Co.

Loose Coupler

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. 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.

Wm. J. Murdock Co.

No. 334 - Loose Coupler

This Murdock Loose Coupler is somewhat larger than the one shown above but was still designed primarily for amateur use. The more robust construction along with the mahogany base implies that this Loose Coupler was for the more advanced amateur willing to spend more money for a higher quality apparatus. Use of the wooden end blocks provides much better support for the primary coil and the horizontal secondary coil guides allow for better alignment. The slider bar is a little more elaborate. The Alexander Bill was attached to the 1912 Radio Act which was signed into law in August 1912 (but didn't go into effect until December 1912.) The Alexander Bill specifically moved amateur operation to 200 meters or below. The most important result of the new regulation was the beginning of experimentation and operation in the shorter wavelengths. The No.334 dates from 1913 or 1914 and its original selling price was about $15.00

Chelsea Radio Co.

Wm. J. Murdock Co.

These variable condensers were generally used with Loose Couplers to provide more accurate tuning 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.

Thordarson

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.

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 usual frequency is around 250Hz to 300Hz.

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.

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 in 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 by 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 was added at a later date. This was a common addition 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.

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 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 (Radiomarine Corp. of  America) until 1922, when WSA was purchased by RCA. RCA/RMCA continued to build and sell the IP-501 and IP-501A until the late twenties.

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.

Standard Assembling Company

The Standard Assembling Company offered this regenerative tuner utilizing a Deforest tuner and Duo-lateral Coils for $50 in 1921. 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.

Adams-Morgan "Paragon" RA-10/DA-2 Receiver

The Paragon was designed by the quintessential ham and 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 a variable condenser in the secondary circuit and a variometer in the plate circuit and 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 superhet, an RA-10 and a proto-type DA-2 were set-up on the receiving table in Godley's 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, at least as far as the hams were concerned.

A.H.Grebe  CR-5

The Grebe CR-5 is a single-circuit tuner with a regenerative detector that uses a UV-200 soft detector tube. 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 or other accessories that Grebe offered. The CR-5 sold for $80 in 1921.

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 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 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.

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 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

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 earliest versions of the IP-501 family were built by Wireless Specialty Apparatus. From 1920 until 1922, all IP-501 type receivers were sold by Radiomarine Corporation of America (a division of RCA) since Wireless Specialty Apparatus was cross-licensed with the RCA/GE/Westinghouse Group. In 1922, RCA/RMCA purchased (or absorbed) WSA along with their manufacturing plant and began building the IP-501 series themselves. The receivers continued to be built up into the late-twenties. 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. The IP-501-A receivers were in use onboard ships throughout the twenties and most of the thirties. They were even pictured in RMCA advertising into the post-WWII period. Most were removed from ships during the late-thirties to early forties. This particular receiver was originally used aboard the Matson Line steamship S.S. Mariposa. I have owned this IP-501-A for over 30 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.