Eighty-five years ago this month, the October 1937 issue of Popular Science carried the plans for this simple transmitter for 160, 80, 40, or 20 meters. The rig was designed with portable operation in mind, hence the small cabinet. To keep it small, the tube, coil, and crystal were mounted on top, which meant that the interior wiring was very uncluttered. A type 47 tube was used, along with a type 80 rectifier. All parts were said to be easily obtainable.

In tests, the rig was able to get out over 500 miles, and the quality was said to rival many larger and more expensive sets.

Any receiving antenna could be used, but a “single wire designed for the proper wave length” was recommended. The article included an interested method of calculating the length of a (half-wave) antenna: “To calculate the proper antenna length in feet, simply multiply the wave length to be covered (in meters) by 1.56.”  While I’ve never seen it expressed this way, this is the equivalent of the familiar 468/f formula.

The author was Donald Levenson, W8PIN.