TM 11-5820-890-30-4
2-3.
RF SECTION.
The RF section consists of five modules.
They are:
Network, Impedance Matching 1A1
lF/Demodulator 1A8
Tuner/Mixer 1A9
Synthesizer, Electrical Frequency 1A10 (synthesizer)
Exciter/Power Amplifier 1A11
The module locations are shown in figure 2-4.
Figure 2-4.
RF Section Module Locations
The impedance matching network provides the impedance matching required for the RT to operate with two
different antenna types.
It provides a 50-ohm impedance when used with a vehicular antenna. To keep the
VSWR below 3.5:1 when used with a manpack antenna, one of the module’s three matching circuits is used. The
module receives frequency data from the control module which is used to select the matching circuit. A detector
in the module checks the VSWR when transmitting with a manpack antenna. If it goes above 5:1, sidetone is
disabled.
The tuner/mixer and lF/demodulator perform basic receive functions. The tuner/mixer filters and amplifies the
received RF signal and mixes it with the local oscillator (LO) signal from the synthesizer. The resulting IF signal is
sent to the lF/demodulator. It demodulates the IF signal to recover the transmitted audio or data signal. The
lF/demodulator detects cue signals during FH operation.
Receive operation is described in paragraph 2-10.
The exciter/power amplifier performs the basic transmit functions. It modulates the RF carrier with the audio or
data signal. It then amplifies it to the required output level. Transmit operation is described in paragraph 2-11.
The synthesizer provides the reference frequencies for the tuner/mixer and the exciter/power amplifier.
2-6
