This circuit was obtained from an American documentation from 1976. The circuit can be adapted to modern TTL components and used as a shield.
This metronome can use either a high impedance phone or a crystal phone. You can use a small...
This circuit can switch signals in the 3.5 to 30 MHz band. We found it in a QST magazine from the...
On this 1960s circuit, stations are pre-tuned in trimmers and then selected by a switch. The...