A hundred years ago this month, the June 1916 issue of Electrical Experimenter magazine carried the plans for this portable wireless set. The author noted that now that summer was in sight, the progressive radio amateur was making ready for experiments with portable equipment. However, it noted that too many sets were made of extra or discarded equipment, with disappointing results.

The set shown here promised good results with an antenna of 150-200 feet, 30 feet high on each end. The receiver was a crystal set with no power needed, and the transmitter would provide many hours of service with six internal flashlight batteries of 4.5 volts each, wired in parallel. Provision was made for six external large dry cells in series. With this power source, the set would produce a 1/32 inch spark. A test buzzer for setting the detector was separately powered with a 1.5 volt dry cell.

The author noted that the receiver pulled in NAA in Arlington, Virginia, in New York City, a distance of 275 miles, and that longer distances could be covered. The transmitter was capable of getting out about two miles, or even five or ten if an audion detector was used at the other end.

The total weight of the set, mounted in a suitcase, was about 14 pounds, and the total cost was about $15. The article notes that this cost was low enough to bring it within the reach of every wireless club or Boy Scout troop.

The author of the article was Milton B. Sleeper (1896-1963), who later went on to publish a number of magazines, such as High Fidelity and FM/TV. About the time of this article, Sleeper was working for Lee De Forest, and he later became a close associate of Major Edwin Armstrong.

The full schematic of the set is shown below, although it contains one perplexing omission.

My first reaction when looking at the schematic of the transmitter was to wonder what made the coil spark, since the primary is connected only to DC, meaning that other than the instant when the key was depressed, there would be no voltage on the secondary.  The article, however, mentions the spark coil’s vibrator, which is not shown in the schematic.  The primary would have an series with it an interrupter, which would rapidly turn the coil on and off, resulting in a square-wave AC current, which would make the transformer work, resulting in a higher voltage on the secondary, sufficient to create a spark.  Since a manufactured spark coil was used, the schematic doesn’t show this detail.

A more complete diagram of a similar transmitter, from a 1920 issue of Electronics World shows the internal wiring of the spark coil:

When the key is pressed, the power from the battery energizes the primary of the spark coil.  In so doing, the magnetic field pulls open the primary vibrator contact, which kills the power to the primary.  With the magnetic field gone, the vibrator contact closes, once again energizing the coil.  The wiring is exactly the same as an electrical bell or buzzer, which operates on the same principle.  This causes the primary of the coil to repeatedly turn on and off, generating a square wave, which induces a larger voltage in the secondary winding, and that voltage is large enough to generate a spark.

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Sixty years ago, the familiar Class D Citizens Band at 27 MHz was still a couple of years away. Class B Citizens Band on 465 MHz had been authorized for a number of years, but as the June 1956 issue of Popular Electronics  pointed out, the service hadn’t gained traction due to equipment requirements:

Equipment for the Citizens band (radio -telephone) must meet specifications set forth by the Federal Communications Commission. To pass these specifications, the equipment must be examined and ap- proved by the FCC in its laboratories. Because of this cumbersome arrange- ment (although fully justified), the design of Citizens radio equipment has for a number of years taken a back seat. The ice has been broken by the Vocaline Model JRC-400 transceiver, which brings Citizens band communication facilities within the reach of everyone’s pocket. After a manufacturer secures FCC approval, he may then produce identical units on an assembly line basis.

The magazine promised further reviews in upcoming issues, but included some observations about the Vocaline unit, which could operate on either 117 volts AC or 6 volts DC. The magazine’s field test showed 100% reliable ranges of 1.5 miles in a metropolitan area or 3 miles in open areas. Out in the country, weak signals were fully readable up to six miles.

The same issue of the magazine carried this ad for the transceiver, showing its retail price of $69.75. The antenna was available separately, and consisted of a quarter-wave ground plane which could be affixed to a vehicle’s roof with large suction cups.

A schematic of the set is available online and reveals that the set used three tubes. A 6AF4 served as superegenerative detector and the oscillator for the transmitter. For audio on both transmit and receive, a 6AV6 and 6AS5 were used. The power supply included a vibrator for DC operation, and included a selenium rectifier.

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This drawing of a well equipped amateur station of a century ago appeared in QST, May 1916. It shows the station of J. Donald Haig of Merchantville, N.J.  The sketch, drawn by Mr. Haig, shows the sending set containing Leyden jar condensers, rotary spark gap, and large oscillation transformer.  The receiver is shown to the left.

QST didn’t give Mr. Haig’s call sign, but according to the 1916 call book, the call was 3QF, and the station was located at 118 E. Maple Avenue in Merchantville.

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Seventy-five years ago, someone looking for an inexpensive radio could get one of these at Walgreen’s for $5.99. This is a bare-bones four tube superheterodyne sold under the Aetna name, which was Walgreen’s house brand, which could have come from a number of factories in the Chicago area. This ad appeared in the Milwaukee Journal, May 28, 1941.

The set appears to be Aetna model 421.  It tunes up to 1700 kHz, meaning it would tune the newly expanded broadcast band, as well as some police calls.  With the war less than a year away and the end of radio production, this set would probably remain in service for the duration.

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In May 1941, the American economy was beginning to boom. Radio Today magazine alerted radio dealers that business indexes were peaking, men were going back to work in increasing numbers, defense jobs were putting money into workers’ pockets. In short, people had money to spend and were earning it.

The magazine showed radio dealers how to go after this money. The magazine noted that extra shoppers were coming to town, and one of the radio man’s jobs was to get them next to bigger radios, like actress Lucile Fairbanks with the GE Musaphonic console shown here.

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