This circuit was found in the July 1986 issue of Radio Electronics magazine. The circuit has a loudspeaker warning system. The sensor is the ceramic capacitor C1 which acts as a transmission line.
This circuit is from an article in the December 1988 issue of Radio Electronics magazine that...
This circuit was found in an American documentation from the 80's. The sensor is a special...
The FET can be a BF245, and the other transistors can be the BC548 and BC558 in this simple AM...