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Setup
signal, and then record the Azimuth and Elevation positions while peaked on satellite (these are the Peak positions).
Again, assure that it has acquired the satellite that you targeted!
Subtract the Peak Positions from the Calculated Positions to determine the amount of Trim which is required. Refer to
the ACU Setup information to key in the required value of Elevation Trim. Continue with Azimuth trim, then re-target
the satellite several times to verify that targeting is now driving the antenna to a position that is within +/- 1.0 degrees
of where the satellite signal is located.
EXAMPLE: The ACU targets to an Elevation position of 30.0 degrees and an Azimuth position of 180.2 (Calculated),
you find that Peak Elevation while ON your desired satellite is 31.5 degrees and Peak Azimuth is 178.0. You would
enter an EL TRIM value of –1.5 degrees and an AZ TRIM of +2.2 degrees. After these trims values had been set, your
peak on satellite Azimuth and Elevation displays would be very near 180.2 and 30.0 respectively.
5.1.
Sat Skew setting
The Satellite Skew setting in the Satellite – Tracking Receiver sub-menu (prior to NID) is used to enter the skew of the
satellite to optimize polarity angle.
This feature is used in conjunction with POL OFFSET to optimize polarization of the feed. POL OFFSET will serve to
calibrate the feed itself (mechanical calibration) Before adjusting the SKEW parameter, target a satellite that is of your
same longitudinal position (ie from Concord, CA at 38N and 122W we would target a satellite value of 122W). Drive
the reflector to 0 or 5 degrees elevation (this is so you can easily view the feed). And verify that the feed is a pure
vertical. This may be visually verified by placing a level bubble on the LNB itself. During Cross-Pol isolation tests, enter
in the known skew value of the satellite, then as instructed by the NOC to drive the feed assembly, increase or
decrease the SAT SKEW parameter. Each digit represented on this screen represents one whole degree of feed drive.
5.2.
Polarity Angle (POLANG) Parameters
First of all make sure that the polang parameters are set correctly:
1.
POL TYPE – should be set to 0072 (Auto-Pol mode).
2.
POL OFFSET – This is initially set to factory default (0040) but will be incremented, or decremented, to
calibrate the feed to the horizon with a level (bubble or digital).
3.
POL SCALE – Leave this at the factory default setting of 0090.
4.
Go to the TX POLARITY parameter in the Setup menu of the ACU and set this parameter to your assigned
Transmit polarity (2=Horizontal or 4=Vertical).
5.
Target your desired satellite (as provided by you airtime provider).
6.
Verify the system has acquired the correct satellite, else continue searching until the correct satellite is
acquired, and set your satellite modem (or spectrum analyzer) to view its signal level display.
7.
Allow tracking to peak the satellite signal.
8.
SAT SKEW – This setting will be incremented, or decremented, to optimize the polarity to peak the received
satellite signal, and later to do cross-pol isolation with the airtime provider, network operation center or
satellite provider.
5.3.
Optimizing Auto-Polarization Cross-Pol Isolation
During commissioning, under guidance from the network operation center, you will be adjusting to minimize the effect
of your transmission on the opposite polarization which maximizes your Cross-Pol isolation. Contact your satellite
provider to help you (over the phone) to optimize the polarity angle for maximum Cross-Pol isolation (this optimizes
your transmit polarity and is much more accurate than trying to optimize your receive polarity).
1.
Verify that tracking is ON and that the antenna is peaked on your targeted satellite (targeting calculates the
azimuth, elevation and polarization angles).
2.
Follow your service provider technicians instructions to set the modem to begin transmitting a CW (pure
carrier) signal.
3.
Go to the SAT SKEW parameter in the Satellite menu of the ACU.
4.
Press the LEFT arrow to edit the current value.
5.
While under direction of the technician (on the phone), press the UP arrow to increment or the DOWN arrow
to decrement the value and then hit the ENTER key to adjust the feed.
6.
The technician should indicate whether the adjustment you made improved, or worsened, the cross-pol
isolation. If it improved he will have you make another small adjustment in the same direction. If it
worsened he will have you make a small adjustment in the opposite direction.
9797B-70 C-Band TXRX
5-2
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Table of Contents
Troubleshooting
