Using a varactor or varicap, this 1969 Electronics World circuit has a modulation range from 75 kHz to 52 MHz. Modern equivalent components can be used.
This is a possible setting for a Colpitts oscillator operating in the audio track. The shunt coil...
We found this circuit in a European publication of the 1980s. The transistor could be the BC549. The...
This programmable circuit emits a signal that can be sensed by the dog at a distance. The circuit is...