When it comes to one tube radios, the holy grail is one that produces loudspeaker volume. And 75 years ago, this humble set from the February 1950 issue of Radio Electronics rose to the challenge. The set used a 3B7 ultraudion with some superregeneration. Regeneration was automatic, and no ticker winding was required on the coil, which was a permeability tuner.

The choice of a volume control was interesting, namely, a wire-wound potentiometer right in line with the antenna. The author noted that the inductance formed part of the circuit, and a carbon resistor shouldn’b be used. The author used a surplus 103.5 volt battery for the B-plus, but noted that two 45 volt batteries in series would be adequate. An outdoor antenna was needed. In areas with strong stations, 25-50 feet would work. But in rural areas, 100 feet as high as possible would be needed.

As an added bonus, the set could be used as a code practice oscillator. The plate of the audio section of the tube was connected through the key to a capacitor to ground.