This crystal or galena radio is one of the many versions available on this website. This is from a documentation from the 70s. The coil is formed by 50 + 50 turns of wire 28 in a ferrite rod.
Found in the 1991 Electronics Experimenter Handbook, this circuit detects voltage variations in...
This well-designed 4-transistor JFET audio oscillator circuit was found in the June 1969 issue of...
This filter is intended for 60 Hz noise suppression in amplifiers. We found it in American...