9500 MXC User Manual
3DB 23063 ADAA - Rev 004 July 2007 Vol. III-5-11
4. Use the cross pole discrimination (XPD) measurement provided in the
Performance screen for RAC 40s to measure the actual V and H signal
discrimination from each antenna.
• Where measured XPDs are better than 25 dB no further adjustment is
needed.
• Where less than 25 dB proceed to the next step.
5. Optimize End-End Feedhead Alignment
This procedure corrects for any minor rotational alignment between
antennas at each end.
One antenna is the reference antenna and its feed-head assembly is not
adjusted during this procedure.
6. Determine which end of the link is to provide the reference antenna, and at the
opposite end open windows to the CT performance screens for the V and H
RAC 40s. Adjust screen sizes and position so that you can see the Cross Pole
Discrimination measurements from both RACs
5
.
7. Adjust the feedhead skew angle of the antenna for maximum XPD on both V
and H RAC 40s. If the maximums for each are at (slightly) different angles,
adjust for a mid-point.
The alignment procedures listed under steps 1 and 2 should result in a
discrimination of better than 25dB, as measured in the Diagnostics >
Performance screen for each RAC 40, which is comfortably within the operating
limits of XPIC. However, for best results and greater operating margins during
fading, feedhead alignment should be optimized using the following procedure.
Only check/adjust skew angles on one antenna. If both antennas are adjusted
and re-adjusted there is potential for progressive misalignment to occur. Select
one antenna as the reference antenna.
On long hops and where fading is prevalent there is potential for the V and H
plane paths to be affected differently and to therefore exhibit variable
cross-polarization discrimination. This alignment procedure must be conducted
during periods of known, stable path conditions.
5
Up to four CT screens can be displayed at once. These may be from the same INU (same IP address) or
from different INUs (or IDUs).
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