Service manual

STP 11-25R13-SM-TG
U - 2
(2) In short-haul systems, the remodulating system offers comparable performance at a lower cost
and with greater flexibility.
(3) For systems up to 8 to 10 hops, the remodulating system is normally used; while for longer
systems, heterodyne equipment is normally used.
U-3. Basic Remodulating Transmitters.
a. The basic remodulating transmitter consists of:
(1) A video amplifier (with preemphasis),
(2) An oscillator which can be modulated,
(3) A crystal-referenced automatic frequency control (AFC) loop, and
(4) A power amplifier and frequency multipliers when required to reach the desired output
frequency as shown in Figure U-1.
Figure U-1. Remodulating Transmitter Block Diagram
b. Various optional items are available to extend the usefulness of the transmitter. These include:
(1) Off-air demodulators to monitor quality of output at antenna feeder input.
(2) Audio subcarrier modulators for transmitting program audio channels.
(3) A switch for rapidly changing frequency to different channels covering 5 percent or more of the
output carrier frequency.
(4) Output filters (wideband or channel width) to further reduce spurious outputs and operate with
diplexers and duplexers.