Sea Tel ST144-21, Installation And Operation Manual

Page: 63 / 142

ST144-21 C/Ku-Band TVRO Setup – Searching
9-1
9. Setup – Searching
9.1. Searching Operation
The ACU will initiate an automated search pattern after AGC falls below the current Threshold setting (indicates that
satellite signal has been lost). The SEARCH DELAY parameter sets the amount of delay, in seconds, that the ACU will
wait after AGC has fallen below the threshold value before it starts a search.
Search can be initiated manually by pressing the
NEXT
key as many times as required to access the SETUP menu, then
press the ENTER Key to access the SEARCH sub-menu and then press the UP arrow key (starts a search from the
current antenna position). While in the SEARCH sub-menu, pressing the DOWN arrow key will stop the current search.
Search is terminated automatically when the AGC level exceeds the threshold value and Tracking begins.
The ACU can be configured to use one of three search patterns. Each of the search patterns are described below.
Each description includes information about the settings involved in configuring the ACU to select that particular
pattern and the values that those settings would be set to, to optimize the pattern for your antenna model and the
frequency band being used.
The dimensions and timing of the search pattern are determined by the SETUP parameters
SEARCH INC
,
SEARCH
LIMIT
,
SEARCH DELAY
and
SWEEP INC
. Search is also affected by the Threshold and the internal receiver
settings under the Satellite menu. To change any one of these parameters, refer to “Changing the Search Parameters”
procedures below.
All three search patterns are conducted in a two-axis pattern consisting of alternate movements in azimuth and
elevation or along the polarization angle. The size and direction of the movements are increased and reversed every
other time resulting in an increasing spiral pattern as shown.
9.1.1.
The factory default search pattern in the ACU is a standard “box” pattern. You configure the ACU to use this
pattern by using the following settings:
Default Standard (Box) Search Pattern
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
– initially set to the default value. After targeting has been optimized, the search
limit can be adjusted if desired.
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 – default value (this parameter is not used in this search pattern).
GYRO TYPE
– must NOT be set to zero.
SAT REF
mode – It is normally
OFF
as long as you have good gyro compass input. It MUST be
OFF
when the elevation angle is greater than 75 degrees. It Must be
ON
if you are experiencing
frequent, or constant, gyro read errors (error code 0001).
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 target the antenna. Initially the antenna will go to a position that is 8 degrees above the
calculated elevation, until Azimuth and Polarization have had time to complete adjustment. Then the
antenna will drive down to the calculated elevation, which is the “Start” of the search pattern in the graphic
below.
The antenna will then search up in azimuth one Search Increment, search up one Search Increment in
elevation, search down two Search Increments 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 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.