TH-3 Microwave Radio System: 4A FM Transmitter and Receiver

FM terminals perform the initial and final modulation steps in non-remodulating type microwave radio systems. T h e 4A FM transmitter converts the baseband signal to a frequency-modulated signal centered at 70 M H z while the 4A FM receiver performs the function of recovering the baseband modulation from the FM signal. The 4A FM terminal equipment will be used to provide improved performance in the TD and T H - 3 microwave radio systems. Design emphasis was placed on: (i) improved performance and reliability; (u) reduced cost and size. The 4A FM terminal equipment (see Fig. 1) is capable of carrying up to 1800 message circuits comprising three multiplex mastergroups or one N T S C color television 2249 2250 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1971 F i g . 1--4A F M t e r m i n a l p a i r .