Research Concepts RC2500 - Manual (Page 37)

30 RC2500 Antenna Controller Chapter 4 Inclined Orbit Satellites
Research Concepts, Inc. • 5420 Martindale Road • Shawnee, Kansas • 66218-9680 • USA www.researchconcepts.com
measurement system of the RC2500. The RC2500 can position an antenna to no better than within
0.005493° of the target position. The actual positioning performance will depend strongly on the
mechanical and electrical drive components of the system. The accuracy of the system depends almost
solely upon the accuracy of the resolvers used. The standard resolvers shipped with the RC2500 have +
7 arc-minute accuracy or + 0.11667°.
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 on the following page. 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 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.