Eighty-five years ago, this young man is making the final tuning adjustments for the one-tube radio he built from plans in the October 1939 issue of Popular Mechanics.

The set was simplicity itself, but it boasted a loudspeaker and AC power, so there was no need to mess around with headphones or a B battery. It was really a crystal set, with a fixed crystal detector. The single tube was a 25A7GT, which combined a pentode AF amplifier with a rectifier. Of course, it had a hot chassis and the familiar “curtain burner” cord to power the filaments.

It was best suited to tune permanently to the same local station. It wouldn’t tune the entire broadcast band without changing the fixed capacitor in parallel with the tuning capacitor, and tuning was very broad. But if you wanted to listen to a local station with loudspeaker volume, the simple design couldn’t be beat.