Figure 5-2. Transmitter Hum Balance Adjustment and modulation Fidelity Test, Equipment Setup.

TM 11-5820-509-35

Figure 5-2. Transmitter Hum Balance Adjustment and modulation Fidelity Test, Equipment Setup.

LOAD controls on the front of the receiver-

c. Procedure.

transmitter for maximum deflection on the

(1) On the RT-671/PRC-47, set the

XMTR OUTPUT meter. Use the OPR-TUNE

KILOCYCLES indicator to 2400; place the CW-

switch to control power amplifier plate power.

FSK/VOICE switch to VOICE, XMTR PWR switch to LO,

Do not permit the power amplifier to operate

and OPR-TUNE switch to OPR.

for more than a few seconds at a time in the

(2) Place the turns-counters of POWER

unloaded condition, serious equipment

AMPLIFIER TUNE and POWER AMPLIFIER LOAD

damage can result.

controls to the settings recommended on the LOAD-

TUNE chart on the front of the receiver-transmitter.

(3) After resonating the power amplifier plate

CAUTION

circuit at the LO setting of XMTR PWR switch, place the

XMTR PWR switch to HI and peak these controls again.

Before making the following measurements

Immediately return the OPR-TUNE switch to OPR

and adjustments, resonate the POWER

AMPLIFIER TUNE and POWER AMPLIFIER

Test

Radio

equipment

control

Test

Performance

Step

settings

procedures

standards

Adjust audio oscillator to

Place CW FSK/VOlCE

Set spectrum analyzer to

Adjust R121 for minimum

2800 Hz and set output

switch to CW-FSK.

2400 kHz and adjust hum

indication at 400 Hz.

level to 0.1 volts.

balance potentiometer

R121 (fig. 3-95).

Return CW-FSK/VOICE

switch to VOICE.

5-6. Transmitter Modulation Fidelity Test

(6) Audio Oscillator TS-382/U

(fig. 5-2)

(7) Primary power source: 115-volt, 400-Hz,

a. Test Equipment and Material.

single-phase, 3 amp.

(1) Spectrum Analyzer AN/UPM-110

(2) Converter, Hewlett-Packard K15-8551B

b. Test Conditions and Equipment Connections.

(3) Dummy Load DA-75/U

(1) Connect the test equipment to Radio

Receiver-Transmitter RT-671/PRC-47 as shown in

(4) Attenuator (see fig. 5-2)

figure 5-2. Do not connect ME-26A/U until instructed to

(5) Multimeter ME-26A/U

do so.

5-3