Thus, substitution of standby equipment applies to the
the ON position. Observe that the associated POWER
following redundant groups: transmitter groups 1 and 2
indicator is illuminated.
(2) The FAULT indicator will remain
downconverter groups 1 the antenna-mounted low noise
illuminated until the stabilization temperature is reached
in the standby LNA (approximately 8 minutes). If
(2) Should a failure occur in a downconverter
desired, place the HI HEAT switch to the ON position to
group the lowest priority traffic group is selected to have
speed up the warming cycle (the HI HEAT indicator will
its service discontinued. If necessary, this procedure
can be repeated until the terminal is operating in a point-
(3) Check that the FAULT indicator is not
to-point mode, i.e., only one transmit-receive condition.
illuminated. Momentarily place and hold the STBY LNA
b. Failure of On-Line Transmitter Group. When a
TEST/ON-TEST switch in the ON position. Observe that
the LNA NORMAL (and TEST OSC) indicator is
failure occurs in either the on-line upconverter,
illuminated; release the switch.
amplifier/mixer, power supply, or power amplifier, all four
(4) Place the ON LINE switch to the standby
units are switched off-line as a complete transmitter
LNA position (No. 2 in this example). Observe that the
ON LINE/LNA indicators change state.
on-line by patching. The modem patching must also be
(5) Turn off power to the failed LNA at its LNA
switched to the standby group.
control panel (No. 1 in this example).
d. Failure of the LNA Waveguide Switch or BITE
has just failed. Assume transmitter group 2 is in standby
Unit Coaxial Switch on the 8-foot Antenna. When the
but now will be switched on-line. Proceed as follows:
(1) Disable the audible alarm.
waveguide switch fails to transfer over, either through its
(2) Place the on-line power supply to the
own failure or loss of the on-line control signal, it can be
operated manually. The ON LINE indicator on the LNA
(3) On the power distribution panel, turn off
control/translator will not indicate a transfer. When the
the circuit breaker to the failed, on-line transmitter group.
BITE unit coaxial switch fails to transfer, it can be
(4) Check that the standby upconverter and
bypassed. If the coaxial switch itself is faulty, the ON
PA klystron are tuned to the assigned transmit
LINE indicator will still indicate a valid transfer, but of the
waveguide switch only. This type of failure will crisscross
(5) Check that ac power is on the standby
the two LNA SHF output signals to the BITE unit and the
upconverter, amplifier/mixer and power supply. Check
downconverters and would, no doubt, trigger multiple
that the power supply is in the standby condition and
receiver fault alarms. Manual operation is the same
there are no fault or status inhibit indications.
regardless of the type of failure. Proceed as follows:
(6) Place the transmit waveguide switch to
the PA2 position.
This procedure should not be
(7) Place the standby power supply to the
performed with the transmitter power
on. On both power supplies place
(8) Enable the audible alarm.
the OPERATESTANDBY switches to
(9) Patch the modem from the failed unit to
the STANDBY position.
the standby unit.
(1) On the rear of the antenna center section,
c. Failure of On-Line Low Noise Amplifier (LNA).
loosen the four captive screws on the MANUAL ACCESS
If the on-line low noise amplifier (LNA) fails, the standby
cover of the waveguide switch.
LNA can be switched on-line to replace it. For example,
(2) Using the switching knob, place the
assume LNA 1 is on-line and has just failed and LNA 2 is
waveguide switch to the selected online LNA position.
in standby. If (warmup) power has been applied to the
(3) Remove the cable from the SHF OUT
standby LNA and its associated FAULT indicator on the
connector on the selected on-line LNA.
LNA control panel is not illuminated proceed to step (3)
(4) At the LNA BITE unit remove the coaxial
below. If not, proceed to step (1) below.
cable from the SHF OUT connector and connect it to the
(1) At the LNA control/translator, on the
SHF OUT connector on the selected on-line LNA.
standby LNA (2) control, place the POWER circuit
Step (4) above bypasses the coaxial
switch in the LNA BITE unit.
e. Failure of the Antenna Control Unit, Elevation
Actuator, or Cross Elevation Actuator on the 8-foot