This circuit was found in an American 1980s documentation. The transistorized step is the receiver's last IF and the diode is the receiver's existing detector.
This is the simplest setting for lighting an LED. The circuit is from old English documentation that got...
Here we have a signal injector for the medium wave range, which uses only one transistor. This...
We found this circuit in a 1975 circuit manual. The operational amplifier is of the old type and...