The plans for this one-tube–er, I mean one-valve–regenerative receiver appeared 85 years ago this month in the January 1939 issue of Practical Mechanics.

The article begins by noting that “the small receiver is apt to be despised in these days of 7 and 8 -valve superhets, there is still a very wide field of application for the simple one-valver. Many schoolmasters, for in- stance, have asked for details of a set which may be used as a demonstrating model, either for handycraft instruction, or to explain many of the theories underlying modern radio technique.”

The circuit relies upon a pre-made coil, which is no doubt unobtainium these days. But the article does describe how to make a very similar coil, which can be used with slight modification of the circuit. Either way, the set did tune both longwave and mediumwave bands, thanks to a band switch which shorted out the longwave portion of the coil. The set uses a D210, which is a British model, but almost any triode would probably work well.