Table D-2. List of Test Frequencies

(5) Power outpug. Refer to figure 1 and connect

titude. Pressure loss shall not exceed 4 pounds per

the RF Wattmeter to the antenna jack J-13 of the

square inch.

Receiver-Transmitter unit using an approximate

(3) Electrical tests. Interconnect the Receiver-

length of (10 feet of RG-9/V) cable. At each fre-

Transmitter RT-742/ARC-51BX or RT-742B/ARC-

quency listed in table D-2, observe that the frequency

51BX and the control C-6287/ARC-51X for the

selection is symmetrically displayed in the read out

Bench Tests as shown in figure 1, 2, and 3 as re-

windows of the control unit. Key the transmitter

quired. Use a RF Wattmeter AN/URM-43A or equiv-

and observe that the transmitter output as read on

alent in place of an antenna. Unless otherwise

the RF Wattmeter, is at least 16 watts. Also note that

specified use "VOL" and "SENS" controls in the

the average output for the 19 channels shall be at

maximum position only.

least 20 watts.

(4) Transmitter tests. For Receiver-Transmitter

RT-742/ARC-51BX use procedure (a), for Receiver-

Table D-2. List of Test Frequencies

Transmitter RT-742B/ARC-51BX use procedure

(b).

(a) Turn on the radio by setting the power

switch on the control to the T/R position. Allow the

set to warm up for approximately 5 minutes before

beginning the tests.

(b) Connect the equipment as shown in figure 1,

and allow a 5 minute warm up period. The RT-742B/

ARC-51BX has a duty cycle of 5 minutes transmit

and 10 minutes receive. During transmit operation,

(6) Sidetone tests. For Receiver-Transmitter

observe this duty cycle ratio. Connect the VTVM

RT-742/ARC-51BX use procedure (a) for Receiver-

(ME-30/U) on the + 10V scale to A6J2, turn the control

Transmitter RT-752B/ARC-51BX use procedure

head frequency to 399.9 MHz on the power ampli-

(b). Refer to figure 1.

fier. Key the transmitter and adjust C6-Z1, C12-

(a) Using not less than 3 widely separate fre-

Z2 and C18-Z3 on the RF preamplifier for maximum

quencies, key the transmitter and talk into the

voltage on the VTVM. Next connect the VTVM to

microphone. The audio output power is 100 milli-

A6J3 and adjust C5-Z1 trimmer on the power am-

watts. Listen to the sidetone output at the headset

H-101A/U to check for normal audio level charac-

plifier for maximum voltage. Adjust C14-Z2 trimmer

teristics. If questionable, check for proper operation

for maximum power out and unkey. Connect the

by feeding a 100 Hz signal into the DUM MIC Jack

VTVM with the positive lead to A6J7 and the ne-

with Audio Oscillator TS-382D/U, at a level of 3 db

gative lead to A6J6 on the power amplifier with the

below clipping (or 70% of clipping). The sidetone

transmitter unkeyed.

output should be indicated as not less than 14 milli-

CAUTION

watts at 30 percent modulation.

(b) Same as (a) above. When the signal input

There is 420 volts on A6J6 and J7 with re-

level on the audio oscillator is adjusted to 3 db below

spect to ground while the transmitter is

clipping the wattmeter shall read 100 milliwatts.

keyed. The VTVM must be isolated from

If the wattmeter does not read 100 milliwatts, ad-

ground.

just R42 (located on the audio module) until 100

(c) After the connections are made, key the

milliwatts is obtained. The sidetone output should

transmitter and adjust A6R11 V4 bias potentiometer

be indicated as not less than 14 milliwatts at 30

percent modulation.

on the power amplifier for 1.5 volts across A6J6 and

(7) Modulation tests. For Receiver-Transmitter

J7. Unkey and disconnect the VTVM. Starting at in-

RT-742/ARC-51BX use procedure (a), for Receiver-

dent 39 on the ten megacycle control proceed to 22

Transmitter RT-742B/ARC-51BX use procedure (b).

checking for power at each position, go back to 39

(a) Refer to figure 2 and connect the test equip-

and perform the power check for the whole and tenth

ment as shown. Set the function switch of the con-

megacycle position. This checks all transmitter

trol unit to T/R + G position and allow the equipment

Xtals.

to warm up for at least 5 minutes. Adjust the audio