This simple circuit for the 3 to 30 MHz range was found in the Electronics Experimenter Handbook Special Projects of 1983. The coils consist of 10 and 50 turns of 32 wire on a 1 M x ½ W resistor.
This automatic control for recording signal level was found in a Radio Electronics from September...
This switched-mode circuit was found in the April 1976 issue of Radio Electronics magazine. The...
This circuit, from a 303 Circuits from the 90s, uses a telephone pickup coil as a sensor to...