Research Concepts RC2500 - Manual (Page 46)

RC2500 Antenna Controller Chapter 4 Inclined Orbit Satellites 39
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'BAND? 0-C 1-K:'. Select the appropriate band for the receiver transponder you wish to initiate the
TRACK function for. The band designation for a hybrid satellite may be changed via the TRACK
menu. The band which the controller assumes is active is displayed in the upper right hand corner of
the display just to the right of the 'TRAK' banner.
11. 'INITIALIZING - PLEASE WAIT' will appear, then the controller will switch to STEP TRACK sub-
mode. The controller will STEP TRACK for 23 hours, 56 minutes, and 4 seconds while building up
the program track table. When program track data is available for the current sidereal time, control
will transfer to the PROGRAM TRACK sub-mode. If the satellite transponder goes down while step
tracking, the controller will switch to SEARCH mode and attempt to require the satellite.
12. The SYSTEM error message at this point indicates that an alarm message is flashing on the bottom
row of the display.
13. If the Search Enable CONFIG mode item is enabled, a good test of the tracking system is to exit
TRACK mode by depressing the MODE key, and selecting the satellite via AUTO mode to reacquire
the satellite. AUTO mode will prompt for the desired polarization and transfer control to the SEARCH
sub-mode of TRACK mode. A search will be performed and when the satellite is found, STEP
tracking will resume.
Please review the description of TRACK mode in chapter 5 for a complete explanation of each of the
TRACK mode submodes and the TRACK mode menu system. Every field of every display screen is
described in that section.
4.4. 4 Tracking Problems
This section discusses problems that can occur while tracking an inclined orbit satellite. TRACK mode
contains an ERROR submode, which displays an error message when it is active. Chapter 7 discusses
all of the possible errors that can occur. This section discusses the most common problems.
The LIMIT error occurs when an antenna limit (either azimuth or elevation) is encountered when tracking
an inclined orbit satellite. This error will only occur while the STEP TRACK or PROGRAM TRACK
submodes are active. The SEARCH submode will not attempt to move outside of the azimuth or
elevation limits. This error generally means that the azimuth or elevation (usually elevation) limits are not
set wide enough.
1. A PEAK LIMIT error indicates that the controller had to move the antenna too far during a STEP
TRACK peaking operation. The maximum movement of the antenna from the starting position for a
STEP TRACK operation is limited. This is to prevent the antenna from peaking up on an adjacent
satellite. This problem can be caused by a number of situations:
2. Specifying too large of an antenna diameter, or specifying Ku band when tracking a C band satellite.
These cause the controller to calculate too narrow of an antenna beamwidth. This beamwidth is
used to determine the maximum allowable movement from the starting position for a STEP TRACK
operation.
3. Specifying too small of a satellite inclination. In STEP TRACK mode, the controller performs peakups
often enough to avoid exceeding the maximum antenna pointing error specified by the Max Track
Error CONFIG mode item. If the specified satellite inclination is too small, the peakups will not occur
often enough, and the antenna may move far enough during a peakup to trigger the PEAK LIMIT
error.
4. The C Band AGC Threshold or the K/L Band AGC Threshold is set too low. If the threshold values
are set too low, when the transponder powers down, the AGC signal of the receiver may be above
the threshold when the antenna is looking at noise. In this case the controller would mistakenly
assume that the satellite signal is present, and attempt to peak up on the noise.
5. If the error occurs during a peakup operation while the PROGRAM TRACK sub-mode is active, it may
be that the Update Check Interval TRACK mode MENU item is set too large.
6. There may not be a sufficient number of position counts-per-degree of antenna movement about one
of the antenna axes. . One ‘count’ is equivalent to 360 / 65,536 = 0.005493°. This number
represents the resolution of the angular measurement system of the RC2500. The RC2500 can
position an antenna to no better than within 0.005493° of the target position If a move of less than
one count is specified the antenna will round the step size up to one count. Note that all systems will
have one count of play or looseness in the antenna - see the next section. A good rule of thumb is