This crystal or galena radio uses a germanium diode. C1 is an old radio variable and L1 has 100 turns of 26 or 28 wire in a 1 inch PVC pipe. The antenna must be a long wire.
This circuit was found in documentation from the 1980s. It is powered by the audio signal that must...
Damped oscillators can be used to produce sound from percussion instruments such as the triangle, bell,...
Found in Radio Electronics from the 90s, this circuit produces pulses to test an infrared...