This amplifier for signals in the 2 m range that corresponds to 150 MHz was found in an American documentation from the 1980s. The FET can be a BF245.
This basic Schmitt trigger was found in an American publication from 1968. The circuit uses...
This circuit is from an American 1964 documentation. Transistors of the time are used, but modern...
This simple circuit uses small speakers for both listening and speaking (microphone). The feeding is...