Service manual

RC2000 Service Manual Chapter 4 Common RC2000 Questions 28
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satellite is passing through the earth's equatorial plane). A peakup will be triggered when the time since
the last peakup equals a value that corresponds to a pointing error of Max Track Error dB at the maximum
angular velocity of the satellite as seen by the antenna. The Max Track Error is specified via CONFIG
mode.
If a peakup triggered by the second event is IN PROGRESS when the first event occurs the peakup
position will not be entered into the table. This can occur on the RC2000B AZ/EL and RC2000B POLAR.
This problem can be avoided with the RC2000C model antenna controllers. The RC2000C allows the user
to specify the amount of time that it takes to perform a STEP track peaking operation. The controller will
not allow peakups just before a sidereal time which corresponds to an entry in the track table. See Section
7.3 of the RC2000C manual.
4.6 TRACK Mode PEAK LIMIT Error
The 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 to prevent the antenna from peaking up on an adjacent satellite. PEAK LIMIT errors
may be caused by the following:
1. 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. The calculated
antenna beamwidth is used to determine the maximum allowable movement from the starting
position for a STEP TRACK operation.
2. Specifying too small of a satellite inclination. In STEP TRACK mode, the controller performs
peakups often enough so that the maximum antenna pointing error specified by the Max Track Error
CONFIG mode item is not exceeded. 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.
3. 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 (antenna iooking
at noise) may be above the threshold. In this case the controller would mistakenly assume that the
satellite signal is present and attempt to peak up on the noise.
4. If the error occurs during a peakup operation while the PROGRAM TRACK submode is active it may
be that the Update Check Interval TRACK mode MENU item is set too large.
5. Play or looseness in the mount. This is discussed in the section on mechanical hysteresis. If the
step size used for peaking the antenna is approximately the same as the mechanical hysteresis,
when the antenna is commanded to move the actuator will be energized but the pointing angle of
the antenna may not change. This can lead to PEAK LIMIT errors.
4.6.1 Mechanical Hysteresis in the Mount
If the controller moves the antenna to the correct position (count value) during an automatic move but the
antenna must be peaked manually to peak up the signal there may be some play in the mount or the
actuator. Note that if the error increases as more movements occur it is probably a sensor problem - see
the section on Antenna Position Sense Errors for more information.
When there is play in the mount the antenna will peak up in one position when approaching the satellite
from the west and another when approaching the satellite from the east. To test for this move the antenna
quite a distance west of the satellite and manually move the antenna east at slow speed until the peak is
reached. Repeat the procedure when approaching the satellite from the east. The difference in azimuth
position between the 2 peaks is the mechanical hysteresis.