RESEARCH CONCEPTS RC2000C Manual page 74

68 RC2000C Polar Tracking Antenna Controller Chapter 7 Troubleshooting/Alarm Codes
DISABLING RUNAWAY ERRORS
The controller has a provision to only allow the accumulation of position counts when the antenna has
been commanded to move, or movement has just ceased (as defined by the Az/El Fast Deadband and
Az/El Slow Deadband CONFIG mode items). This has the effect of disabling RUNAWAY errors. It is
generally not recommended to disable the runaway error. If necessary, it can be accomplished by setting
the Az/El Fast Deadband CONFIG mode item to a value which ends in '01', i.e. 2001, 2301, etc.
THE PROGRAM TRACK TABLE HAS GAPS EVEN THOUGH THE SATELLITE TRANSPONDER HAS
NOT POWERED DOWN
In the STEP TRACK sub-mode, the controller periodically peaks the antenna. Two events can trigger
a peaking operation. The antenna will peakup at the sidereal times corresponding to entries in the track
table, and store the peak azimuth and elevation antenna positions. A peaking operation will also occur
whenever the controller calculates that the antenna pointing error could exceed the error specified by the
Max Track Error CONFIG mode item because of the satellite's apparent motion. The controller calculates
this time interval by knowing the satellite's inclination, and calculating the antenna beamwidth based on
the antenna size and frequency band.
Since the track table has 48 entries and a sidereal day is 23 hours, 56 minutes and 4 seconds long, a
track table-inspired peakup will occur roughly every 30 minutes. A problem can arise if a Max Track Error
inspired peakup is in progress when the track table peakup should occur - the controller will not perform
the track table peakup, and no azimuth and elevation position data will be stored in the track table. This
causes gaps in the track table data (which may be examined via the TRACK MENU - VIEW function). To
prevent this from occurring, the controller will not initiate a Max Track Error peakup within 120 seconds
prior to a sidereal time which corresponds to a track table entry. The 120 seconds is referred to as the
Peakup Holdoff Interval.
The user can change the Peakup Holdoff Interval by manipulating the value of the Az/El Slow Deadband
CONFIG mode item. If the Az/El Slow Deadband CONFIG mode item is a multiple of 50, the default
value of 120 seconds is used as the Peakup Holdoff Interval. The user can select any Peakup Holdoff
Interval (up to 500 seconds) by selecting a Peakup Holdoff Interval which is not a multiple of 50.
The relationship between these two items is illustrated by way of an example:
Az/El Slow Deadband = 818 milliseconds
818 divided by 50 equals 16 with a remainder of 18. For this case the Peakup Holdoff Interval will be (18
* 10) or 180 seconds.
The Peakup Holdoff Interval should be longer than the worst case time that it takes to perform a peaking
operation. The worst case peakup time will correspond to the portion of the satellite's apparent motion
when the satellite is passing through the earth's equatorial plane.
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