Sea Tel ST144-21, Installation And Operation Manual

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ST144-21 C/Ku-Band TVRO Setup – Searching
9-3
9.1.3.
If the ship does not have a gyro compass to use as a heading input to the Antenna Control Unit, you may
manually key in the actual heading of the vessel and then re-target the desired satellite, every time you need
to re-target a satellite, or configure the ACU to do a “No Gyro Search Pattern”.
No Gyro Search Pattern
You configure the ACU to use this pattern by using the following settings:
SEARCH INC
- set to the default value for the frequency band that your antenna model is currently
being used for (typically 15 counts).
SEARCH LIMIT
– leave this set to the default value.
SEARCH DELAY – default, or any number of seconds from 1-255 that you would prefer that the
ACU wait before starting an automatic search.
SWEEP INC
– Larger antennas should have slower speeds and smaller antennas should have faster
speeds:
Larger antennas should have slower speeds set to 0047 (= 5 degrees/second) for 2.4M to
3.6M antenna systems).
Mid size antennas can be driven a little faster, set to 0063 (= 8 degrees/second) for 2M
antennas models).
Smaller antennas should have faster speeds, set to 0079 (= 18 degrees/second) for all
0.8M to 1.5M antenna models).
GYRO TYPE
– MUST be set to zero for this search pattern.
SAT REF
mode –
MUST
be
ON
for this search pattern.
Target any satellite longitude value which includes even tenths digit values (ie SAT 101.0 W or SAT 101.2 W).
If the desired satellite longitude includes an odd tenths digit, you must round it up, or down, one tenth to
make the tenths digit EVEN. The Antenna Control Unit calculates the Azimuth, Elevation and Polarization
values it will use to target the antenna. However, without heading input, the ACU cannot target a “true
azimuth” position (relative to true North). It will target the antenna to the calculated elevation and a
repeatable “Start” relative azimuth position. In Series 04 antennas this relative position will be 90 degrees
away from the nearest mechanical stop. In all other antennas it will be 000 degrees relative.
Initially the antenna will go to the “Start” relative azimuth position at the calculated elevation. Then the
antenna will search up 450 degrees in azimuth, search up one Search Increment in elevation, search down
450 degrees in azimuth, search down two Search Increments in elevation, etc until Search Limit is reached.
When the end of the search pattern is reached, the ACU will retarget the antenna back to the start point
shown in the graphic below.
If the desired signal is found (AND network lock is achieved in the satellite modem) at this position, or
anywhere within the search pattern, the ACU will terminate search and go into Tracking mode. If the desired
signal is not found the ACU will wait SEARCH DELAY seconds and then begin the search pattern again. This
cycle will repeat until the desired satellite signal is found or the operator intervenes.