Radio Craft Magazine, December 1936

        

How To Make The World's Smallest 3-Tube Radio Set

The December, 1936 issue of Radio Craft magazine shows a natty gent wearing his new battery-powered radio, complete with stylish antenna hat!

Amusing in retrospect, this radio was cutting-edge for its time, and considerably predated the coat-pocket portables of the late 1940s, shirt-pocket transistors of the 1960s, and Johnny-come-lately devices such as the Sony Walkman or Apple iPod.

This Special Radio-Experimenter Number of Radio Craft includes complete instructions for building the radio.

Portable radios had been around as early as the 1920s. Zenith made its "Companion" in 1924, for example. However, these early portables were the size of a small suitcase, weighed as much as a sack of bowling balls, and could not be played while carried.

By 1936, when the article was published, radio technology was still heavy and bulky. Nothing this small would be commercially available for about another 20 years, when subminiature tubes and more efficient batteries made it practical to sell a tube radio that you could play while walking.

This wearable mini-radio did not involve any technological breakthroughs. It is a regenerative receiver, a somewhat outdated design compared to newer superheterodynes. Simplicity is the advantage of a regenerative set, however. Only one of the radio's three tubes does the receiving. The other two merely amplify the signal.

Considerable ingenuity was needed, along with miniature components, to fit a radio into such a tiny package. Two of the batteries are attached to the listener's belt, while a third is slipped into a trouser pocket. The article describes this as an "unspillable liquid" battery, which probably means it was a lead-acid type containing corrosive acid. Let's hope that those batteries never leaked!

Since the human body acts as a capacitor, antenna construction and location were tricky, and the radio's frequency range was limited.

Nevertheless, the New York author claimed to have received stations from as far away as Cincinatti. The same radio might be hard pressed to duplicate that long-distance feat today, when the airwaves are much more crowded than in 1936.

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