Section III. PRINCIPLES OF OPERATION

TM 11-5820-882-23/TM 06827A-23/2

Sensitivity- . . . . . . . . . . .

.. .

. .0.5 uV for 10 dB

Frequency stability -------------------------------------- 0.005 percent

Spurious and harmonics radiation--------. ----------50 dB below rf car-

SINAD*

rier level

Squelch sensitivity ---------------------------------------0.5 uV

Modulation limiting ------------------------------------- 15 kHz deviation

Selectivity: 6 dB down------------------------------bandwidth greater

(maximum)

than 15 kHz

Squelch tone (2.5--3.5 kHz deviation) -------------- 148 to 152 Hz

60 dB down------------------------------bandwidth less than

50 kHz

Response to spurious signals -------------------------- 60 dB

RECEIVER

Frequency stability -------------------------------------- 0.005 percent

Audio output ---------------------------------------------less than 10 percent

Adjacent channel rejection ---------------------------- 60 dB

distortion at 20

Image rejection ------------------------------------------- 40 dB

q SINAD =

Signal + Noise + Distortion

Noise + Distortion

Section III. PRINCIPLES OF OPERATION

1-9. General Information

When the radio set is in the transmit mode (unit turned

on and PUSH TO TALK switch depressed), the speaker/

The radio set contains eight plug-in modules which pro-

microphone is used as a microphone to apply a voice

vide all the circuitry necessary for receive and transmit

signal to the modulator/mixer. Here the signal is fre-

operation. These operations can be broken down into

quency modulated on a carrier singal determined by the

two basic functions, described below.

synthesizer and voltage controlled oscillator (controlled

1-10. Receiver Opration (fig. 1-3)

by the frequency select switches). The output of the

When the radio set is turned on (PWR OFF/ON/

modulator/mixer goes to the transmitter module where

SQUELCH DIS switch in the ON position), the unit is

it is amplified to 1 watt minimum. The antenna coupler

in the receive mode (squelch is on, no receiver noise pre-

matches the transmitter circuit impedance to the anten-

sent). Signals entering the antenna are routed through

na (long or short) for maximum power transfer.

the antenna coupler to the converter stage. The frequen-

cy synthesizer and voltage controlled oscillator (vco)

1-12. Secure Voice Operation

provide a mixer frequency for the coverter stage. This

Secure voice operation may be utilized on the radio set

mixer signal is determined by the setting of the frequen-

by connecting the secure voice module (svm) to the bot-

cy select switches (three located on the synthesizer

tom of the rt unit. The battery case and battery must be

module and one located on the top panel of the radio

removed first. The svm connector (located next to the

set). After the incoming signal is converted to a 12.0

battery connector) has a small black shorting plug in-

MHz signal, it is routed to the filter/i-f module for

stalled. This plug must be removed to install the svm in

amplification and a second conversion to 6.5 MHz and

its place. If the radio set is not being used with secure

then to the i-f/a-f module. The intermediate frequency

voice equipment, the shorting plug must be installed in

and audio frequency (i-f/a-f) module detects and

the svm connector for normal set operation. The re-

amplifies the signal and connects it to the built-in

tainer (attached to SVM plug) must be wrapped around

speaker/microphone or external handset.

the connector before installation of plug to prevent

1-11. Transmitter Operation (fig.1-4)

damage to retainer line.

1-2