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
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It is a regenerative receiver, a somewhat outdated design compared to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.