Found in 1965 Radio Shack documentation, this circuit has a crystal phone output in the 14.8 kHz range. The coil consists of 200 turns of wire 25 in a 1.5 m side square.
Varicap or varactor is the basic component used in this circuit of an American 80's documentation. The...
This circuit was obtained from the October 1977 Radio Electronics magazine. The meter is analog, and...
This circuit doesn't use CMOS functions, but instead a bipolar transistor. The main feature for...