COBHAM SEA TEL 9711IMA-70, Installation Manual

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9711IMA-70 Optimizing Cross-Pol Isolation
13-1
13. Optimizing Cross-Pol Isolation
Now that all of the other setup items have been checked and changed as necessary, it is time to contact the NOC to arrange
for cross-pol isolation testing and whatever other commissioning the NOC asks for. Read this procedure thoroughly before
you are asked to begin. Assure that you are on the correct satellite and have RX network lock. (the NOC may have you
adjust TX Frequency and/or modem TX level prior to beginning cross-pol isolation). At the appointed time follow the steps
below for the cross-pol isolation testing.
13.1. Optimizing Cross-Pol Isolation
1. Access the Tools - Position Antenna
screen.
NOTE: You will use Skew to optimize polarization
because it drives the feed immediately (Linear
Offset is slower, longer term drive).
2. Record the value in the Skew field in the
upper section of the screen. If this
satellite has a known Skew, it will be
entered in the satellite configuration
displayed here. If this satellite is not
skewed this field will be 0.0.
3. While talking to the technician at the NOC
make adjustments to the Skew value to
adjust polarity of the feed under his/her
direction (minus values are accepted –
type a minus sign before the number
value). It is best to adjust in one degree
increments to get close to best isolation
and then half degree steps and then
tenths as needed. Click “Submit” after
each numeric change is typed in.
4. Record the DIFFERENCE in Skew value
which was required to achieve optimum
cross-pol isolation.
5. Set Skew back to the value recorded in
step 2.
6. Access the Reflector Configuration
screen.
7. Change the “Linear Offset” value by the
amount of difference recorded in step 4.
Examples:
Skew was 0.0, you increased it to 2.5 to optimize
TX polarization. You set Skew back to zero and go
to the Reflector Configuration screen where you
find Linear Offset to be 0.0, so you increase Linear
Offset to 2.5 degrees and click Save.
Skew was 3.0, you decrease it to 1.0 to optimize TX
polarization. You set Skew back to 3.0 and go to
the Reflector Configuration screen where you find
Linear Offset to be 0.0, so you set Linear Offset to
minus 2 (-2.0) degrees and click Save.
EAR Controlled - ECCN EAR99