pulling radio signals out of thin air as if by magic. Not all crystal sets take this slapdash approach, of course, and some, like this homebrew multiband crystal receiver, aim for a feature set ...

Learning by building a crystal set is ubiquitous. A how-to book from East Germany on radio with a crystal set prominently featured. Get back to basics and make a crystal radio. Learn about ...

The earliest and cheapest radio set for the home was ... to a small piece of mineral crystal such as galena, which received and converted the signal to audio that can be listened to on headphones.