Found in an old American documentation this FM modulator makes use of a varactor diode. The circuit can be easily implemented given the small number of components used.
This variable power supply circuit was found in a German publication from the 1980s. The circuit is...
This circuit is suggested by Texas Instruments and is based on a relaxation oscillator with...
In the figure we have a typical Wien Bridge oscillator with AGC. The negative waveform is sampled by...