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TM 11-5820-890-30-5
4-2.
POWER SUPPLY. Continued
DC Output
Maximum
Maximum
Voltage (V dc)
Current (A)
Ripple (mV p-p)
6.75 (6.55 to 6.95)
1.5
75
13.0 (12.6 to 13.4)
4.3
75
200 (180 to 220)
0.008
3000
These outputs are short-circuit protected. The power supply will not be damaged if an output is shorted to
ground.
4-3.
AUDIO AMPLIFIER.
The audio amplifier performs the following functions:
Amplifies the audio input to 1 W to drive a loudspeaker.
Amplifies the audio input to 200 mW for the intercom set.
Detects FSK (TACFIRE) tones to generate the required control signal.
Additional filtering of 13 V dc line.
A functional block diagram of the audio amplifier is included in figure 4-1.
a.
One-Watt Audio Amplifier. The analog receive (AR-A or AR-B) signals from the RT are amplified by
the 1 W audio amplifier. The output level is determined by the RT VOL control setting. An input signal of 5.5 V rms
will be amplified to 1 W into 600 ohms. The frequency response is from 300 to 3000 Hz. An analog switch is used
to attenuate the output when either PTT line or the MUTE line is grounded.
b.
Intercom Audio Amplifiers. The analog receive signals from the RT are also amplified by the intercom
amplifiers. AR-A and AR-B are amplified separately to 200 mW. The output level is determined by the RT VOL
control setting. The frequency response is also 300 to 3000 Hz.
c.
FSK (TACFIRE) Detector. The FSK permits using one radio for audio and analog data. The analog data
mode control (ADMC) line at the transmitting RT must be grounded when the analog transmit (AT) signal is
analog data and AD2 is used. The FSK detector does this for the user.
It is a four-stage process. The AT signal is amplified to the required level. A notch filter attenuates all frequencies
outside the 300 to 3000 Hz range. This prevents harmonics from triggering the tone detector. The tone detector
checks for the 1200 and 2400 Hz FSK tones. If both are present and the FSK PRESENT signal passes to the output
processing circuit, the output processing circuit begins when a PTT is received. The ADMC line is held open for
120 ms after a PTT. After 120 ms, the output of the tone detector is checked. If FSK tones were detected, the
ADMC line is grounded until PTT is released. If the tones were not detected in the 120 ms period, the line is held
open until the PTT is released. A separate FSK detector is provided for AT-A and AT-B.
4-4.
MOUNTING ADAPTER CHASSIS.
The mounting adapter chassis provides the basic radio interconnections as shown in figures FO-14 and FO-15.
Several other functions are also performed. The power input is switched on and off by CB1. EMP protection is
provided by CR1 through CR6, VR1, VR2, and E9 through E15. The remote control transformers couple the RT
and control-monitor. The SNAP line driver passes signals between RT A and the SNAP. Q1 and R1 are
electronically part of the voltage regulator on the audio amplifier.
4-2
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