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(7) Restore the HP-200AB ATTENUATOR
723A/U (used as a vacuum-tube voltmeter)
setting to the position determined as noted
should be not greater than 0.02 volt.
in (4) above.
(7) Reestablish the standard receiver test
(8) Set the RT-505/PRC-25 function switch
conditions; use the HP-200AB to externally
to RETRANS. The test assembly RE-
modulate the 1066A.
TRANSMIT lamp should light and the
(8) Without changing the RT-505/PRC-25
TS-723A/U (used as a vacuum-tube volt-
VOLUME control setting, determine the
meter) should indicate receiver audio
receiver audio output level produced with
output. The RETRANSMIT lamp pro-
modulation frequencies of 300, 500, 2,000,
vides a convenient method of monitoring
and 3,000 cps (at 10-kc deviation). Ac-
operation of the squelch circuit.
ceptable frequency response is +0, 6 db
(9) Momentarily set the RT-505/PRC-25
(from the 1,000-cps reference) at 300 cps,
function switch to OFF then back to
and +3, 6 db at 500,2,000, and 3,000 cps.
RETRANS to verify that the receiver will
c. Limiting Test
unsquelch (RETRANSMIT lamp lighted)
(1) Perform the limiting test with the equip-
with an RF input level of 0.5 microvolt.
ment connected in a standard receiver test
(l0) Slowly decrease the RF input level at the
setup (para 102 and fig. 79.7), except set the
RT-505/PRC-25 coaxial ANT input to
RF signal level at the RT-505/PRC-25
0.35 microvolt. The receiver should re-
coaxial ANT input to 1 microvolt.
main unsquelched.
(2) Adjust the 1066A frequency for minimum
(11) Disconnect the 1066A RF output from the
distortion as checked on the TS-723A/U.
receiver coaxial ANT input. The receiver
(3) Increase the 1066A output to produce 100
should squelch, the lamp associated with
millivolts at the RT-505/PRC-25 coaxial
ANT input.
test cable No. 1 should go out, and the
TS-723A/U (used as a vacuum-tube
(4) Readjust the 1066A frequency for minimum
voltmeter) should indicate no receiver
distortion. The new audio output level
audio output.
on the TS-723A/U (used as a vacuum-
(12) Reduce the 150-cps modulation to zero
tube voltmeter) must be within 3 db of
and increase the 1,000-cps modulation to
the original setting (of 1 volt).
produce l5-kc deviation. Set the RF level
d. Squelch Sensitivity and Retransmit Tests.
at the RT-505/PRC-25 coaxial ANT jack
(l) Perform the squelch sensitivity and re-
to 10 microvolt. The receiver should not
transmit test with the equipment con-
nected in a standard receiver test setup
e. Catching Range Test.
(para 102 and fig. 79.7) except set the RF
(1) Perform the catching range test with the
s i g n a l level at the RT-505/PRC-25
equipment connected in a standard receiver
coaxial ANT input to 0.5 microvolt, the
test setup (para 102 and fig. 79.7), except
R T - 5 0 5 / P R C - 2 5 function switch to
set the 1066A and the RT-505/PRC-25
SQUELCH, and modulate the 1066A
to 31.50 mc. Place the RT-505/PRC-25
simultaneously at 1,000 cps and 150 cps as
upside-down for this test.
described in (2) through (7) below.
Caution: Check to see that the RT-
(2) Set the 1066A SET MODULATION con-
505/PRC-25 is set to a frequency ending in
trol fully counterclockwise.
50 ( XX.50 ) when disengaging the coupling
(3) Use a 10-second count on the AN/USM-
in the procedure in (2) below; otherwise
26 to adjust the output frequency of the
the coupling may become damaged.
HP-200AB to 150 Cps 1.5 cps.
(2) Disengage the mechanical coupling finger
(4) Set the HP-200AB output level to produce
(fig. 3, TM 11-5820-398-20). This dis-
3-kc deviation on the 1066A. Accurately
ables the crystal switching assembly from
determine and record the AMPLITUDE
module A10. To disengage the coupling,
control setting.
fabricate a tool from a piece of sheet metal
(5) Set the HP-200AB AMPLITUDE con-
that measures 1 by 4 inches and is between
trol fully counterclockwise.
0.018 and 0.035 inch thick (20 to 26 gage).
(6) Adjust the 1066A SET MODULATION
Insert one end of the sheet metal tool into
control to produce 10-kc deviation.

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