Implications of Phase Precompensation in A Television Transmitter on the Shape of the Radiated Signal

The smears after black-to-white transitions due to phase errors in the receiver can be compensated by an overshoot introduced by a phase-precompensating network in the video-frequency section of the transmitter. In a negative-modulation system this overshoot can only be accommodated in the available modulation space by raising the maximum-white level from 10 per cent, to at least 20 per cent, which is equivalent to a loss of transmitted signal power of 30 per cent. Curvature of the modulation characteristic makes a complete compensation impossible. With a positive-modulation system, the output stage of the transmitter should be capable of delivering pulses, reaching to 22 per cent, over and above the maximum-white level.