Experimental Transversal Equalizer for TD-2 Radio Relay System

The TD-2 radio relay system 1 employs frequency modulation to transmit multichannel telephony or television. The frequency modulated signal requires a transmission system whose gain and envelope delay are constant over the frequency band, 20 me wide, used to transmit the signal. Deviations from constant gain or delay result in non-linear distortion of the demodulated signal. For television this results in distorted images, and for multichannel telephone transmission this introduces cross modulation among the voice channels. Basic equalization is provided in each repeater. In addition, certain fixed equalizers have been used on a mop-up basis. However, there remains some residual distortion of random shape. This paper discusses the design of an adjustable equalizer to compensate for this distortion.