Found in an American 1980s documentation, this circuit compares signals from two TTL sources, providing an output that depends on the frequency difference. The circuit can be used as a shield.
This circuit was found in a Popular Electronics from the 90's. The circuit has gained 10 to 20 dB...
This simple circuit uses a car ignition coil. The circuit appeared in the 1983 Radio Electronics Annual...
The modified Hartley oscillator seen in the figure can generate signals ranging from 3 MHz to 10...