We found this circuit in a Radio Electronics from December 1963. The circuit combines valves and transistors and has a high input resistance. The circuit is powered by two batteries.
This circuit uses an MW radio tuned to around 540 kHz to detect atmospheric signals, for example, from...
This project was found in a 1982 publication. It is a small transmitter that can send signals from...
This circuit is from a 1960 book by Hugo Gernsback. The transistors are germanium from the time....