Eighty years ago this month, the April 1937 issue of Popular Mechanics carried the plans for this simple 40 meter transmitter employing a single 6L6 tube. The set used an 80 meter crystal, and according to the article, using the crystal on its second harmonic resulted in particularly good keying.

The set called for a power supply delivering 400 volts at about 100 milliamps.

It was said to have a range of about 500 miles.