Found on 80's Popular Electronics this circuit operates at 455 kHz. The explorer coil is formed by 10 turns of yarn 26 in a 4 inch shape. The indicator is a microammeter.
This circuit was found in a 90's Electronic Design. The circuit can be adapted to use modern...
This circuit makes a very fast switch when receiving an input signal. The FET can be BF245 and the...
White noise applied to an audio amplifier can be used as a relaxant, since it resembles the noise...