Using a common crystal diode and a 741, this circuit can be used to detect microwaves. The circuit is from old documentation and the switch selects the gains.
This 1950's circuit used one of the first commercial transistors and had two stages for audio...
Using integrated circuits from the time, we found this audio compressor in an English publication from...
This is an experimental crystal radio that uses no power source. The antenna must be very long (at...