This circuit was found in an old documentation for radio amateurs. The circuit makes use of an uncommon integrated today. The circuit converts telegraph signals to be used on the computer.
Using a capacitor as a sensor, this circuit can detect signals from 50 MHz to 500 Hz, according to the...
Although MOSFETs of the type indicated are not very easy to obtain, one can have the circuit as a...
Found in Radio Electronics from the 90s, this circuit generates signals in the 60 Hz to 1.4 Hz...