(2) Each input channel of the amplifier/mixer
selects the auto track mode.
(c) Autotrack. The autotrack mode uses a step
contains directional couplers for sampling the SHF
signal. The coaxial switch on the SHF MONITOR
track algorithm to keep the antenna alined to the
section of the front panel can select a sample of each
maximum satellite signal. This method of tracking can
input for measurement after input level adjustment; it can
be considered as a hill-climbing or peak-signal-seeking
also select an unfiltered sample of SHF output.
technique. A step-by-step description of the tracking
Other SHF samples from the SHF drive assembly and
algorithm function is to step the antenna in the elevation
the SHF output assembly are monitored by the RF low-
axis by + 0.020 (0.060), integrate the receiver tracking
power-alarm module. The alarm module lights the front-
video voltage for 0.5 second, return the antenna to the
panel FAULT lamp when RF drive is present, but output
center position, step the antenna in the elevation axis in
is below a predetermined level.
the direction opposite to that of step 1 by 0.020 (0.06),
(3) Two power-supply modules provide low
integrate the inverted tracking video receiver voltage for
voltage dc power to the amplifier/mixer drawer. These
0.5 second, return the antenna to the center position,
voltages, and the TWT beam current, can be monitored
examine integrator value and make a decision on the
at the STATUS MONITOR meter. A third power supply
direction of the scan which gave maximum power, allow
provides power for the TWT amplifier.
antenna to remain still for an average of 4 seconds, and
Antenna Control Unit. The antenna control unit
repeat all of the preceding steps in the cross elevation
can control either of two types of motorized antenna
structures. These structures are the AS-3036/TSC (8-
foot diameter) or AS-3199/TSC (20-foot diameter).
a. Modem. Modem MD-1002 has independent
(1) Angle control. The antenna control unit
transmit and receive circuits which modulate and
controls antenna pointing angles by means of motor
demodulate the IF, utilizing biphase shift keying (BPSK)
drive actuators which provide antenna motion in
and quadraphase shift keying (QPSK). The data rate for
elevation and cross elevation.
The actuators are
each circuit may be selected independently, depending
controlled in the antenna control unit by an amplifier
on the mode of operation.
operating within a closed servo loop. Antenna control is
Multiplex Unit AN/FCC-98
provided in three modes of operation; manual,
consists of three different circuits: the transmit and
acquisition, and autotrack.
signal acquisition and fully automatic tracking of the
and the data circuits. The transmit-receive multiplexing
satellite is provided, using signal strength information
circuits produce a mission bit stream of from 196 kb/s for
from either the beacon signal or from a communication
three-channel operation to 1.5440 Mb/s for 24-channel
signal, both of which are detected by the comm-track
operation. The circuits also produce and accept only
module. A step track algorithm is used for autotracking
NRZ mission bit stream (MBS). The voice circuits
with either of the two antenna systems.
(2) Mode selection. The control modes are
occupy one 64 kb/s time slot. The data circuits are
selected by a front-panel switch on the antenna control
divided into three independent circuits: 0-20 kb/s, 50
unit or from the remote control unit (which when plugged
kb/s, and 56/64/128/256/512 kb/s. The 0-20 kb/s circuit
in disables the similar functions in the antenna control
requires no clock input. The 50 kb/s circuit requires a
unit and so indicates by lighting the REMOTE ON
clock input normally provided by Converter CV-3034.
The 56/64/128/256/512 kb/s circuit require a clock from
(a) Manual mode. The manual mode
the user. The 56/64 kb/s circuit occupies one 64 kb/s
allows the operator to position the antenna by using the
time slot and the 125/256/512 kb/s circuits occupy 2, 4
axis control switch, which selects left, right, up or down
and 8 64 kb/s time slots respectively.
c. Encoder/Decoder. The encoder/decoder unit
(b)ACQ (acquisition). In the acquisition
KY-801 is connected to the modem to provide a better bit
mode, the servo automatically conducts a spatial search,
error rate (BER) while transmitting and receiving the
using a cross elevation bar covering an area 5.6 degrees
mission bit stream.
wide in cross elevation and 0.8 degree in elevation for
d. Line Conditioning Equipment.
the 20-foot antenna and 13 degrees by 0.8 degree for
frequency line conditioning equipment consists of three
the 8-foot antenna. Upon detection of a signal, an
universal shelves and replaceable modules for
acquisition command from the receiver commands the
processing up to 12 user VF channels configured for the
antenna to stop and the track loss lamp to go out. The
following traffic modes:
operator can then optimize the signal, using the axis
control switch. After assurance that the main beam has
been acquired, the operator then