Amplitude-modulated transmitter Class-C output stage. Operating conditions when the load impedance varies over the working frequency band

The mode of operation of the amplitude-modulated transmitter Class-C output stage is discussed, with particular reference to the case where the load impedance varies over the working frequency band; a typical example is that of a long-wave broadcasting transmitter. The impedance presented to the anode must be symmetrical with respect to the carrier frequency if non-linear distortion of the radiated signal is to be avoided. The carrier can be modulated fully at high audio frequencies if the impedance rises symmetrically (but not if it falls symmetrically) on each side of the carrier frequency.