(1) Tune the upconverter synthesizer to 8200
coupler and connect the cable to the RF power meter
MHz, and the receiver to 7500 MHz.
and low power head HP-8484A using a UG-29B/U
(2) Connect the limiter assembly, SM-A-
934943, input to the SHF LO output of the upconverter
(8) Set the upconverter to 8399 MHz and the
synthesizer with the 6-foot test cable W401, SMC-
downconverter to 7699 MHz and measure and record
935488-1. Insert a 14 dB attenuator in series with the
the signal level.
loop test cable at the shelter wall.
( 9) Repeat step (8) above at 8200 MHz and
(3) Disconnect the SHF output cable from J8
7500 , MHz.
on the rear of the LNA control/translator drawer and
(10) Repeat step (8) above at 7950 MHz and
connect to the output of the limiter assembly, SMA-
(11) Disconnect the loop test cable from the
(4) Connect the HP-436A power meter, using
power meter and connect it through the 14 dB attenuator
the HP-8481A power head, to the IF output of the
to the LOOP TEST coupler.
downconverter drawer. The IF output level of the
(12) Calculate and record the input levels for
downconverter should be 50 dB minimum above the
each frequency by subtracting 14 dB from the measured
coupler input level. The IF output level may be adjusted
levels of steps (8), (9) and (10) above.
at the 700/70 MHz mixer assembly, A2A1, in the
(13) Connect the power meter with the
downconverter drawer, with the receiver gain adjustment
HP8481A head to the 70 MHz OUTPUT (J4) of the
R5 or MDL gain R6.
downconverter to be measured.
(14) Read and record the measure level. The
b. Test Procedure.
level should be at least 50 dB above the level calculated
(1) Remove the feed-tube from the antenna
in step (12) above.
center section and replace it with a dust cap or aim the
(15) The overall receiver gain may be
antenna at a quiet spot in the sky.
measured for receive frequencies of 7250 MHz and 7699
(2) Loosen the captive screws on the front
MHz by tuning the upconverter synthesizer to 7950 MHz
panel of the upconverter drawer and pull the drawer
and 8399 MHz, respectively. Output levels should be 50
forward on its slides.
dB minimum above input.
(3) Disconnect cable W5 going from the
synthesizer of the upconverter at J2 on module A4 and
downconverters as required.
connect the same to the hard limiter test assembly, SM-
(17) Replace the antenna feed; remove all test
A-934943, through test cable assembly SMC-935488-1,
cables, and restore all normal connections on the
and the SMA adapter provided in the test kit.
drawers to return the shelter to normal operation.
(4) Loosen the screw fasteners on the front
panel of the LNA control/translator drawer, and pull the
8-7. Frequency Accuracy
drawer forward on its slides.
The frequency accuracy tests are intended primarily for
(5) Disconnect connector A2P53 going to
diagnostic purposes in locating malfunctioning units
receptacle J8 (SHF out) at the rear of the LNA control/
which are causing gross frequency error. The test
translator drawer, and connect it to the output of the hard
equipment available at this general support level of
limiter test assembly, SM-A-934943.
maintenance is not sufficiently accurate for adjustment of
(6) Configure the shelter for normal operation
the 5 MHz reference oscillators in the synthesizers of the
and turn the power ON, except that the PA is left on
upconverters and downconverters. For the following
(7) At the antenna mounted assembly,
disconnect the terminal loop test cable from the LOOP