Seventy years ago, these picnickers were enjoying a favorite radio program while on their outing, thanks to their portable radio. But they would have never thought of it if it weren’t for the foresight of their radio dealer in suggesting one.

The picture appeared in the May 1951 issue of Radio & Television Retailing magazine, which pointed out that most people were not “portable conscious.” The dealer needed to help them out through advertising in the store, especially in connection with summer gift-giving occasions such as graduations and weddings. And while the magazine was gearing up for the summer season, it reminded readers that the fall hunting season or Christmas were just around the corner, and it was a good idea to plant the seed.

The magazine suggested exchange advertising. For example, an excursion boat line might be interested in placing a poster with rates in the dealer’s shop, in exchange for an ad for the radio shop at the ticket office.

This hundred-year-old circuit, from the March 1921 issue of Radio News, initially had me a little mystified, since the accompanying article describes the set as a “C.W. transmitter.” But I searched in vain for the rectifiers in the power supply and found none.

The mystery was solved by loyal reader NM0S who pointed out that it’s not exactly a CW transmitter–it’s actually a modulated CW (MCW) transmitter, which puts out a 120 Hz tone. He points out that this is the same type transmitter employed by Art Collins, 9CXX (later W9CXX and then W0CXX), to make contact with an Arctic expedition in 1925. There’s no rectifier because the tubes plates are hooked directly to the AC. As you can see, one tube is hooked to each end of the transformer winding, meaning that each one of them will be “on” for alternating halves of a cycle. As a result, the output will be modulated with a 120 Hz tone, meaning it can be copied with any receiver, even a crystal set.

The manufacturer of the set is not stated, only that it is an “eastern radio corporation” that had recently entered the market, and had been on display at a recent radio convention at the Hotel Pennsylvania in New York.

The set was designed for operation with two type U.V. 202 tubes, and even though the tubes were rated at five watts each, the set could be run at an overload of 100 percent, for an output of up to 20 watts, at the cost of reduced life of the tubes. The magazine noted that the set would be suitable for places such as summer camps. It reported one notable QSO during the daytime between 1DH in Boston and 1DAC in York Harbor, Maine. This was accomplished with an antenna of only 27 feet, one foot above the roof.

Shown here is a one-tube transmitter for 80 or 40 meters from the May 1951 issue of Radio News.

The 12-watt set’s main feature was its compact size. The author, Leon Wortman, W2LJU, noted that he knew at least one ham who had stayed off the air “because of the apartment shortage.” Whenever that ham expressed a desire to get back on the air from his cramped apartment, he wife protested that there was no room for equipment, nor even room to hang her nylons. The transmitter itself measured only 3 by 5 inches, although it also called for a similarly compact power supply which could be tucked away. The transmitter itself was crystal controlled using a 6V6GT.

Voltage doubler. Wikipedia image.

The power supply employed a 117 volt isolation transformer, but used a voltage doubler circuit to supply the B+. The author noted that the circuit was by no means new, and was employed in many receivers. However, it was rarely used in ham gear, and it was intriguing to think that you could take a voltage and double it without the use of inductors or transformers. It does this by charging a capacitor on each half of the cycle, and then placing those in series. In this case, the unit employed selenium rectifiers.

Eighty years ago today, the May 19, 1941, issue of Life magazine carried this ad for a Zenith portable. While the model number isn’t given, it appears to be model 6G601.  The six-tube set ran from a non-rechargeable battery pack, or from AC power.

The distinguishing feature of the Zetith portable was the Wavemagnet antenna.  This was a loop antenna contained in a cardboard cover that looked like a horseshoe magnet.  It came with suction cups to attach it to the window of a car, train, or building.  The compartment with the antenna also had a storage area for headphones for private listening or for the hard of hearing, although they were an optional extra.

The set retailed for $29.95 with airplane fabric cover, or slightly more for genuine cowhide.  Prices were also slightly higher in the west.  According to this inflation calculator, that works out to the equivalent of $544 in today’s money.

If the set looks familiar, it’s because we’ve featured it previously.

A demonstration of a nicely restored example of this set can be seen in the video below.

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Sixty years ago, the May 1961 issue of Radio Electronics showed how to assemble this four-transistor pocket radio. Many items of this era were billed as being “about the size of a pack of cigarettes,” but this one really was. The cabinet was constructed using a cigarette flip top box.

The magazine gave detailed instructions for constructing it. The first step was to carefully cut off the top where it hinges. Various slots were added, and additional cardboard inserts were placed inside for various compartments. At this point, the cardboard box was painted with two coats of Duco household cement, thinned down to a paintlike consistency with laquer thinner or nail-polish remover.  After this was thoroughly dry, you would paint the box with your favorite color enamel and let it try for a few days. The top would be sanded lightly or steel wooled to allow the top to fit back on snugly. The finishing touch was calibrating the dial with the customary markings of 53 through 16 with a “toy printing or rubber-stamp set.” Each number was held with tweezers, coated by a piece of glass with a thin coat of paint, and pressed to the case.

Blueprints for the cardboard cabinet.

The chassis could be a standard printed circuit board, and the magazine showed the pattern. Or, another option was to build a circuit board using another piece of cardboard treated with the diluted Duco.

After all that work building the handsome cabinet, you wouldn’t want to skimp on the electronics, and this circuit didn’t. It used a Philco AO-1 transistor as the regenerative detector, along with three of the venerable 2N107 transistors as audio amplifier. The receiver was tested by the publisher, and performed quite well. From the test location 20 miles from New York City, the set was able to pull in nine stations with good earphone volume. It noted that it probably could have heard more stations with careful tuning. The loudest station, which was seven miles away, was loud enough to be heard by two persons with the earphone in a small dish on the table between them.

The author reported similar good results at his location. He noted that it was very selective over the entire broadcast band. He reported at night hearing stations 400 miles away, and three stations 1500 miles away. He also reported that on local stations, he could listen with the earphone six feet away.

This utilitarian but handsome receiver graced the cover of the May 1951 issue of the British magazine Radio Constructor. That issue, as well as the June issue, described the circuit and provided details on putting it together. According to the author, the magazine had received numerous requests to design such a set, and those requests asked that the set should be easy to construct, compact, and provide a pleasing symmetrical cabinet.

Those requirements posed a tall order, but with some experimental work, this set, dubbed the “Constant Companion” was the result. The three-tube (including rectifier) circuit tuned the long and medium wave bands, and provided loudspeaker volume with a suitable antenna.