This high impedance headphone amplifier was found in American documentation from the 1990s. Any general-purpose FET can be used.
We found this elementary receiver in a 1983 publication, but it can be easily assembled today, as any...
This oscillator was found in a 1976 documentation. The no specified components indicate circuit...
The figure shows how to use a varicap in a conventional tuning circuit. The circuit may be an...