Radio Principles

The pulses at the gate cause pulse currents at the collector and the resulting collector voltage becomes a sine wave due to the action of the tank circuit. When the tank is tuned to the required harmonic of the input it acts as a filter, rejecting all other frequencies. Chaining several of these together can create very high frequencies. Buffer amplifiers (where gain is unity, impedance in is high and out is low) are usually put between the class c amplifiers to prevent loading. The tank circuit is built to high specs to prevent instability. An LC circuit will not have the tolerance of a crystal oscillator but the overall stability comes from the original crystal circuit.