(1) Check that the POWER circuit breaker is
Under normal operating conditions, the
in the ON position and the associated POWER indicator
amplified RF noise alone from the LNA
is illuminated on the LNA control/translator, the LNA
will cause a mid-scale indication on the
control (of the LNA under test), and the downconverter.
downconverter IF OUT position of the
The FAULT indicator on the LNA control
RCVR FAULT indication will occur if the
will be illuminated when ac power is
IF OUT level drops below 1/4 scale on
applied to a cold LNA.
the MONITOR meter.
approximately 5 to 8 minutes for the
LNA to reach operating temperature and
d. Receive Signal Level Too Low at Modem, but
become stabilized. The HI HEAT switch
No Fault Indication at LNA Control or Downconverter.
may be placed to the ON position to help
(1) Check for antenna pointing error.
speed up the warmup period, if desired.
(2) If a received carrier level as indicated by
(2) If the LNA control FAULT indicator does
the modem MONITOR meter is low or absent, check the
not turn off at the end of the warmup period, proceed to
interconnecting 70 MHz signal cable between the
step b below. If the FAULT indicator does turn off at the
downconverter and the modem.
e. Faulty On-Line LNA Indication (Standby LNA
end of the warmup period, proceed to the appropriate
fault indication of step c, d, and e below.
Downconverter RCVR FAULT Indicator both Illuminated.
The standby LNA may be tested at any
(1) The LNA is probably defective. Switch the
time using the test controls on the LNA
LNA to STBY and test it according to paragraph e below.
If the test shows the performance of the LNA to be
(1) After sufficient standby LNA warm-up time
satisfactory, replace the LNA control module (para 5-42)
(15 minutes desirable), hold the STBY LNA TEST/TEST
and proceed to step (2) below.
switch to the ON position.
(2) Observe that the TEST OSC indicator is
synthesizer OUT OF LOCK indicator is illuminated, test
the downconverter in accordance with the procedures in
(3) Observe that the LNA NORMAL indicator
is illuminated; if illuminated, the standby LNA gain is
(3) If the operation of the frequency synthesizer
is normal, place the MONITOR switch on the
at other frequencies may be accomplished, if desired, by
downconverter to the IF OUT position and note the
tuning the LNA BITE oscillator as described in paragraph
MONITOR meter reading. If the reading is less than 20,
test the downconverter in accordance with the
(4) If the LNA NORMAL indicator does not
illuminate when testing one LNA, but does when testing
c. RCVR FAULT Indication at Downconverter, No
the second LNA, the first LNA is probably defective and
FAULT Indication at LNA Control (On-line LNA Testing).
should be replaced. BITE adjustment checkout should
(1) Test the downconverter in accordance
be made at the antenna (as described in para 5-54) prior
to removing the suspect LNA.
(2) If the performance of the downconverter is
(5) If the LNA NORMAL indicator does not
found to be satisfactory in step (1) above, and the fault
illuminate when testing either LNA, and other LNA
appears to be due to low RF level at the downconverter
control/translator indications are normal, the LNA BITE
input, (see note below) switch the LNA to the STBY
adjustment should be checked as described in
position and test according to e below. If the LNA is
satisfactory, visually inspect the SHF coaxial cabling
BITE may be faulty.
from the SHF output of the LNA (on the antenna) to the
SHF input of the downconverter.
Removal and Replacement of Low Noise