RF Sensitivity Test.

TM 11-2826-258-24

Readout AN/USM-207, or equivalent, to

(f) PHASE ANGLE SELECTOR to 0.

monitor the test frequency output of Signal

(4) Set Radio Test Set AN/ARM-92B controls as

Generator SG-1A/ARN.

follows:

e. Audio Output Test.

(a) OFF/PWR/TEST to PWR.

(1) Set rf signal generator for a 1000-microvolt

(b) Frequency dial to 114.90 MHz.

output signal at 114.90 MHz modulated 10 percent by

(c) IND TEST to V/L RCVR.

1000 Hz.

(d) BEARING (switch) to BRG.

(2) The audio output meter shall read at least 50

(e) BEARING (control) to 0.

milliwatts.

( 5 ) Set Audio Output Meter TS-585/U

f. Agc Flatness Test.

IMPEDANCE to Xl, 150 and MULTIPLY by 1.0.

(6) Adjust SG-lA/ARM FREQUENCY dial for

(1) Set rf signal generator for a 1000-microvolt

output signal at 114.90 MHz modulated 30 percent by

peak on RF MONITOR meter.

1000 Hz.

(7) Adjust SG-lA/ARN RF LEVEL control for

(2) Note audio output meter reading in db.

redline indication on RF MONITOR meter,

(3) Slowly vary the output the rf signal generator

(8) Adjust SG-lA/ARN MOD LEVEL control for

between 10 microvolt and 10,000 (10K) microvolt.

full scale (30 percent) indication on PERCENT

The audio output meter shall not vary more than k 10

MODULATION meter.

db from noted reading.

(9) Set MD-83A/ARN SPECIFIC SIGNAL

g. VOR Course Width Test.

SELECTOR to 9960FM. The SG-1A/ARN PERCENT

(1) Set up a standard VOR test signal.

MODULATION meter should indicate 30 percent.

(2) Set the radio test set BEARING switch to

NOTE

OBS.

If a 30-percent indication is not obtained in

(3) Set the radio test set OBS control to N (north).

the preceding step, open the potentiometer

door on the MD-83A/ARN front panel and

NOTE

adjust the 9960 FM potentiometer for a 30-

The OBS indicator on the radio test set must

percent indication on the SG-lA/ARN PER-

be an ID-1347C/ARN.

CENT MODULATION meter.

( 4 ) Set the m o d u l a t o r PHASE ANGLE

(10) Set SG-lA/ARN MOD RANGE switch to

SELECTOR for O on radio test set DEVIATION meter,

100%.

Note the PHASE ANGLE SELECTOR setting.

(11) Set MD-83A/ARN FUNCTION SELECTOR

(5) Adjust the modulator PHASE ANGLE

to ODR.

SELECTOR for 150 microampere (positive) deflection

d. RF Sensitivity Test.

on radio test set DEVIATION meter. Note the PHASE

(1) Set rf signal generator for a 5-microvolt output

ANGLE SELECTOR setting.

signal at 114.90 MHz modulated 30 percent by 1000

(6) Adjust the modulator PHASE ANGLE SE-

Hz as follows:

LECTOR for 150 microampere (negative) deflection

(a) Rf signal generator MOD switch to 1000~.

on radio test set DEVIATION meter, Note the PHASE

(b) Rf signal generator MOD RANGE switch to

ANGLE SELECTOR setting.

30%.

(7) Compare the three PHASE ANGLE SELEC-

(c) Adjust rf signal generator MOD LEVEL

TOR readings. The second and third readings must be

control for 30 percent indication on PERCENT

10 2 from the first reading.

MODULATION meter.

h. VOR to/From Ambiguity Test.

(2) Set radio test frequency to 114,90 MHz.

(1) Set up a standard VOR test signal.

(3) Note audio output meter reading in decibels.

(2) Set the PHASE ANGLE SELECTOR on the

(4) Turn rf signal generator MOD switch to EXT.

modulator to 0.

Audio output meter shall read at least 6 db lower than

(3) Set the OBS control on the radio test set to N.

noted reading.

(4) The TO-FROM meter on the radio test set

(5) Repeat steps (1) thru (4) with Radio Test Set,

must indicate between 500 and 1200 microampere to

and rf Signal Generator set to the following fre-

the left of zero.

quencies:

(5) Reduce the output level from the rf signal gen-

106.00

111.30

114.60

117.90

erator to 5 microvolt.

109.10

112.40

117.95

115.70

(6) The TO-FROM meter on the radio test set

110.20

113,50

116.80

must indicate between 500 and 1200 microamperes to

NOTE

If unusual or defective receiver performance

the left of zero.

(7) Reset the output level of the rf signal genera-

has been noted on a specific channel frequen-

cy, perform the rf sensitivity test on that fre-

tor to 1000 microvolt.

(8) Set the PHASE ANGLE SELECTOR on the

quency. Use Electronic Counter, Digital

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