This converter has coils according to the reception and converted frequency bands. We found it in the October 1989 Radio Electronics magazine in an article that teaches its construction.
This is the normal circuit of a relaxation oscillator using an unijunction transistor such as the...
This super metal detector uses three coils, operating in differential form with two transmitter and...
We found this amplifier with high input impedance and low capacitance, using FET, in a...