This circuit responds to frequencies from 100 Hz to 3 MHz. We find it in a 90s Radio Electronics. Transistors are general purpose types.
This anti-bounce circuit was found in a 1967 US documentation. Modern transistors such as the...
This circuit is an improvement over the previous one, using the same capacitor system as a sensor....
This good gain antenna up to 30 MHz was found in an American 1990s documentation. The circuit can be...