This circuit for signals up to 30 MHz can improve your reception in the medium and short-wave band. We found it in the Radio Electronics magazine of February 1989.
This oscillator has its frequency controlled by crystal and its frequency can be between 100 kHz...
This small crystal microphone transmitter was indicated in an 80s spy book. The range depends on...
The circuit shown is from the 1994 Linear Applications Handbook by National Semiconductor. The...