Research Concepts RC2000C - Manual (Page 35)

RC2000C Az/El Tracking Antenna Controller Chapter 4 Inclined Orbit Satellites 27
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factor is entered by the user. The azimuth scale factor can either be specified by the user, or it can be
derived from the position and Longitude data of adjacent geostationary satellites. Scale factors are
discussed in more detail in the next section.
The use of the Intelli-Search algorithm relieves the user of the task of having to specify the controller's
search region. Other tracking antenna controllers limit the search to a box shaped region and force the
user to determine the boundaries of the search region, which is often a trial and error process. Please
refer to figure 4.2. If the box shaped region specified by the user is too small the controller may not
search the entire region where the satellite's apparent motion takes it, and for some segments of the
satellite's movement, the controller may not be able to find the satellite. If the box search region is too
large, the controller may find an adjacent satellite. If the search region is not centered properly, both of
the error conditions described above could occur.
The Intelli-Search algorithm calculates the shape of the search region based on easily determined
physical data supplied by the user, and information derived from the antenna positions and longitudes
of the geostationary satellites in the vicinity of the inclined orbit satellite which is being tracked. In most
cases the search region is shaped like a parallelogram. The long dimension of the parallelogram is
calculated based on the satellite Inclination angle specified by the user when the track is initiated from
SETUP mode. The width (or short dimension) of the parallelogram is specified by the Search Width
parameter entered via CONFIG mode. The Search Width has a range of values of 1 to 10, with 1
specifying the narrowest search window and 10 specifying the widest window. The default value of 3 is
adequate for most situations.
If a satellite signal is found during a search, the controller switches to the STEP_TRACK submode. If a
satellite signal is not found during the search, the unit waits awhile and then performs another search. If
during the wait the sidereal time advances to a value for which there is valid track table data, the
controller will switch to the PROGRAM_TRACK mode. The wait period between successive searches
is determined by the value of the Search Retry Interval parameter. The default value of this parameter
is 10 minutes, but it can be changed to any value between 0 and 999 minutes via the TRACK menu.
The search consists of successive sweeps separated from one another by an angle corresponding to a
2-dB rolloff of the antenna pattern. The antenna pattern is calculated based on the Antenna Size and
frequency Band. The controller will usually sweep in azimuth, increment the elevation angle, and then
sweep again in azimuth. This will continue until the entire search region has been covered. The
automatic search may be enabled or disabled via the Search Enable CONFIG mode item. When the
automatic search is disabled, the user is prompted to manually jog the antenna onto the desired
satellite, and then hit the ENTER key.