Shows the technology of Frequency Modulation in action. A slow addition of current to the input capacitor on the oscillator transistor's base, decreases the capacitance of the tank circuit, and hence increases its resonant frequency, to make it output a higher frequency wave. This in effect superimposes the input signal onto the carrier wave, which then needs to be amplified, here by a class A mechanism, to have any useful transmission range.
This one uses the upper end of the official FM radio range, 115 megahertz.
