The November 1937 issue of Popular Science carried the plans for this midget one-tube regenerative receiver for the broadcast band using a dual-grid type 49 tube.  The notable feature of the tiny set was that it employed only a single battery, a 3 volt “A” battery that powered the filaments as well as supplying the modest B+ voltage.

The low power requirement apparently meant that the set was just a bit finicky, since the article cautioned that many of the parts had to be exactly as specified in the article.  But when done, the midget tube set was said to produce good headphone volume with 10-20 feet of insulated wire tossed on the floor as the antenna.

The modest battery requirement meant that the set was ideal of hikers and campers, or for use in isolated areas without electric power.

Midget tube receiver schematic