Suggested by a 90s Popular Electronics this circuit is intended to receive volleys or whistles from thunderstorms in the wave range below 20 kHz. The coil consists of 300 turns of wire 26 in a ferrite rod.
This circuit was obtained from an English circuit manual. Components are common and LEDs can be 3...
Found in a 90's EDN, this circuit generates signals in the frequency range given by the graph. The...
This circuit can generate signals from 100 kHz to 1 MHz depending on the L1 coil. For the medium...