Seventy years ago, the September 1945 issue of Popular Mechanics carried the plans for this “Tom Thumb” crystal set, about the size of a match box. The circuit was very basic, with no variable condenser, instead using a simple slider across the coil to tune. The coil was flattened, and wound on a 5/8 by 1-9/16 by 2-5/8 inch block of wood. It notes that this block is recessed at one end to take a small fixed detector. For a modern replication, a diode could easily be used, with many sources for obtaining it noted on my crystal set parts page.
The article notes that the block should be baked in a moderate oven before winding the coil, presumably to drive out moisture. The slider is made of a partially flattened Fahnestock clip, and the “cabinet” is constructed of cardboard. The outside contains four more Fahnestock clips for the antenna, ground, and headphones. The article notes that in areas with a strong station, about 20 feet of wire tossed on the floor should give adequate reception, with a spring clip attached to a convenient ground.
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