TM 11-5895-846-14
(1) With the antenna properly pointed to the
Side-lobe levels are 15 dB down from the main lobe or
satellite, the terminal receives communications SHF
better.
signals in the frequency band of 7250 to 7750 MHz and
(7) Received communications SHF signals at
converts these to 70 MHz signals. It also receives a
the antenna receive flange are fed to a redundant
beacon signal in the same frequency band which is
receiver section of the terminal (defined as that portion of
converted and detected as a low frequency control signal
the terminal from the receive antenna feed to the 700
for directing the acquisition and tracking function of the
MHz or 70 MHz IF output) consisting of a low noise
antenna system.
amplifier (LNA) and downconverter.
The LNA's are
(2) The antenna group for the AN/TSC-86
mounted on the back of the antenna center section with
terminal consists of an eight foot parabolic reflector and
the other antenna mounted electronics (fig. 2-5).
attached electronic package. The movable part of the
(8) The received signal from the antenna is
antenna is supported in a wide yoke which is controlled
routed through a test directional coupler and wideband
by cross-elevation and elevation actuators. The antenna
preselector to a changeover switch which is used to
is mounted on a double tripod space frame structure.
place LNA #1 or LNA #2 in the on-line mode via controls
Each axis is driven by a linear actuator.
Satellite
on the LNA control/translator unit inside the shelter.
tracking is accomplished by a random step scan using
(9) A Gunn oscillator, located in the LNA BITE
the satellite beacon signal as a data source.
unit and energized from the LNA control/translator,
(3) Antenna
signal
acquisition
is
provides a test input signal for checking the performance
accomplished by placing the MODE switch on the
of the standby LNA. The Gunn oscillator injects a signal
antenna control to the MANUAL position and using the
to the input of the off-line LNA. The off-line LNA can be
axis control switch to scan through the area of
physically removed without affecting terminal operation.
uncertainty while observing the carrier level meter for
(10) After 39 dB amplification in the low noise
signal acquisition. Upon acquisition of the satellite's
amplifier the signal is carried by coaxial cable via a
beacon signal in the manual mode, decrease the MGC
directional coupler and a power splitter to the online
switch to the lowest level that will maintain a track signal.
downconverters in the shelter equipment.
The
This procedure will provide a fine adjustment between
downconverters are dual frequency conversion units.
the satellite and antenna. The final antenna adjustment
The five downconverters are each complete units
will be made by placing the MODE switch to AUTO
containing a frequency downconverter, synthesizer and
TRACK. This will allow the Antenna Control Unit to track
power supply.
on the signal strength automatically. These procedures
(11) The downconverted 70 MHz signal from
may be made using either the Antenna Control Unit
each on-line downconverter is then routed to the
(ACU) or the Remote Control Unit (RCU).
communications subsystem for additional processing
(4) After satellite acquisition, the tracking loop
and the 700 MHz signal is routed to the entry panel.
is closed and a random scan pattern is initiated. The
c. Communications subsystem (CSS). The CSS
scan pattern is a randomly determined series of motions
provides the interface and signal processing functions
of one or two second periods at 0.05 and 0.1 degrees
between the individual field user lines and the RF
which are applied to the elevation and cross-elevation
subsystem of the AN/TSC-86 terminal. Baseband and
axis. The sequence has a 50 percent duty cycle (64
signal conditioning equipment included in the CSS
seconds cross-elevation, 64 seconds off, 64 seconds
provides processing of user VF, teletype and digital
elevation and 64 seconds off).
signals into a single PCM signal. Bulk encryption of this
(5) Half hemispheric (180) coverage is
signal is provided by the TSEC-KG-81 prior to application
provided without vehicle orientation, although limited
to the QPSK/BPSK digital data modem. The 70 MHz
tracking motion of + 12.5 degrees is provided.
This
output from the latter equipment is applied to the
sector can be oriented to any point in space by the
transmitter section of the RF subsystem. A central
setting of the double tripod antenna mount and selection
distribution frame (CDF) included as a portion of the CSS
of the linear actuator drive position.
Both open loop
houses a matrix programming board which provides a
manual control of the drive motors and emergency use
traffic path reconfiguration capability.
of a hand crank at the actuator are provided in the
design. Either of these manual drives can be used for
d. Other Functions. Other functions are provided
the initial acquisition or for emergency manual track.
(6) The reflector-feed arrangement provides a
in the terminal including separate external standard
minimum aperture efficiency of 55% which, for the eight-
interfaces that allow all reference frequencies and local
foot reflector, gives a minimum receive signal gain of
oscillator sources of the transmitter and receiver to be
42.5 dB and a minimum transmit signal gain of 42.5 dB.
derived from external frequency standards.
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