A Theoretical Analysis of Single-Sideband Operation of Television Transmitters

The effect of detuning a transmitter to suppress partially one sideband and increase the width for the other sideband is investigated. A screen-grid tube driving a simple tuned circuit is assumed. It is also assumed that the tube operates as a class C amplifier and is grid modulated. To establish simple criteria for the performance of the circuit, the voltage amplitude across the tank in response to "unit-function" modulation is studied as a function of the circuit decrement and detuning. The "time of response" is defined as the time required for the tank-voltage amplitude to build up to 0.632 (1-1/e) times its steady-state value. The time of response is found to be a function of the decrement and detuning. It decreases with an increase in decrement or an increase in detuning. The "decay time" is defined as the time required for the tank voltage to drop to 0.368 (1/e) times the initial value and is found to be equal to the reciprocal of the decrement. The effect of detuning on the carrier-power output is considered. It is assumed that the anode dissipation of the tube is limited and that the operating parameters are adjusted to the optimum values consistent with the specified values of decrement and detuning. It is shown that detuning results in a severe reduction in power output.