This two-tube circuit, one being a double, was found in Radio Electronics magazine from July 1958. The distance to the microphone depends on noise and losses. The cable must be shielded.
This converter converts a signal in the 200 kHz to 3.8 MHz band into frequency signals that can be...
This is the receiver for the previous circuit. The audio amplifier supports equivalents. The...
This circuit is from Radio Electronics from February 1987. The frequency is given by the crystal that...