This circuit was found in a 1965 General Electric documentation. It is intended for reception of the aviation strip, but inside an aircraft or nearby (which is now prohibited).
Found in a 1965 Radio Shack documentation this oscillator can be used with modern general purpose...
In the figure we have the way to use a single control voltage to act on two varicaps...
Found in a 90s documentation, this switch that is also sensitive enough to operate capacitively uses...