This circuit covers the bands from 1.8 to 150 MHz, with plug-in coils whose characteristics are given next to the diagram. The FET can be a BF245. We found it in old documentation.
This circuit using an operational amplifier was found in old American documentation. It can be...
If the circuit oscillates, emitting sound, it is because the transistor is good. This simple...
Like the previous circuit, this is used in the analog part of the telephone lines. The same...