TM 11-5895-846-14
(b) There are five downconverters in the
This panel allows control of ac power, selection of
normal or high heat, and control of the parametric
terminal complement. Normally, four downconverters
amplifier and FET stages during testing of the LNA when
are on line and provide four independent 70-MHz or 700-
it is in standby condition. Fault circuitry in the LNA is
MHz IF output signals. The fifth downconverter (No. 1 or
connected to a FAULT lamp on the LNA control panel to
No. 5) is used for tracking or is in standby condition.
indicate failure of the unit out-of-tolerance voltages or
temperature.
receives 70-MHz IF signals from the CSS or 700-MHz IF
(b) LNA BITE assembly. The LNA BITE
signals from an external source by way of the IF patch
assembly switches the output of either LNA to the
panel. The IF signals are converted to a transmit
receiving equipment in the shelter. A second function of
the unit is to generate and detect a test signal for testing
the off-line LNA. When energized by a switch on the
carrier mode or in multicarrier modes using up to four
LNA control/translator, an SHF oscillator in the BITE
carriers. However, the multicarrier modes may be used
assembly generates a test signal. This signal is routed
only with the 20-foot Antenna AS-3199/TSC, since the 8-
through the standby LNA and re-enters the LNA BITE
foot antenna is not controlled for intermodulation product
assembly, where is detected. If the gain of the LNA is at
suppression. In the single carrier mode, either antenna
least 37 dB, the detected output causes the LNA
type may be employed. The RF output from the power
NORMAL lamp on the LNA control/translator panel to
amplifier is routed through a manual waveguide switch to
light.
the antenna feed waveguide, or to a dummy load for test
(2) Received signal distribution.
After
purposes. At the antenna, the RF output is applied
entering the shelter at the receive antenna entry panel,
directly to the antenna feed horn assembly.
(1) Upconverter. The upconverter is the first
the SHF signals pass through a directional coupler
having a minus 8 dB secondary port. Output from the
unit in the transmit chain of the radio subsystem. It
secondary port is routed to downconverter No. 5, while
signals exiting the through-port pass to a 4-way power
subsystem (CSS) or from an external source, and
divider which provides equal signal distribution to
translates it to a transmit frequency between 7900 MHz
downconverters 1 through 4. Downconverter No. 5
and 8400 MHz using double conversion techniques. It
receives approximately the same signal level as the
can also accept a 700-MHz IF and convert it to SHF by
other four. A second directional coupler is placed
single conversion. The output of a single upconverter
between the 4-way divider and downconverter No. 1. The
may be fed directly to a power amplifier (PA) for single
secondary port of this coupler provides a test signal
carrier operation. For multicarrier operation, the outputs
which appears at the RF test patch panel. Antenna
of up to four upconverters are combined in the
tracking through satellite beacon or communications
amplifier/mixer drawer for application to a single PA.
(2) Amplifier/mixer. The amplifier/mixer
signal is selectable at the track patch panel. Beacon
signal tracking requires the exclusive use of one
drawer combines the SHF out-puts of two, three, or four
downconverter, leaving the balance to support the
upconverters onto one single lead and amplifies the
multiple carrier requirement. All downconverters include
combined signal. The combined output is connected
through the transmit patch panel to the input of one of
output ports. Each of the former ports terminate at the IF
the two power amplifiers. The amplifier/mixer drawer
patch panel for routing to the CSS modems, while the
provides isolation between the circuits to be combined,
latter from downconverters No. 1 and No. 5 feed the
amplification of the combined signal, input and output
track patch panel for distribution to the tracking system.
level setting controls, and power monitoring and alarm
(3) Downconverter. The downconverter uses
functions. There are two amplifier/mixer units in the
a dual or single downconversion technique to convert the
terminals.
(3) Power amplifier high voltage power
input SHF frequency (7250-MHz to 7750-MHz) to an IF
frequency of 70 MHz or 700 MHz. The downconverter
supply. The power amplifier (PA) and its power supply
can be tuned through the receive frequency range in l-
(HVPS) are individually packaged units which are
kHz increments by direct- reading front-panel switches.
interconnected by the required cabling.
Although
(a) The downconverter contains a
physically separate, the PA and HVPS operate in the
frequency synthesizer, a power supply, a downconverter
terminal as one functional unit, and are not capable of
mixer module, and BITE circuits.
independent operation.
There are two PA/HVPS
6-10