General Dynamics 500-0646, Руководство по эксплуатации

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500-0646A 38
Step 4. When the antenna is being peaked to the maximum copolar signal level, it is
necessary to make sure that the antenna is on the main beam and not a sidelobe of
the signal (see Figure 32).
•
If the antenna is on a side lobe the signal on the spectrum analyzer will diminish and
not return or will decrease and return to a higher level as the antenna is rotated in
azimuth and/or elevation (see Figure 33).
•
If the signal diminishes and does not return, position the antenna back to the original
starting point. Rotate the antenna in the opposite direction. The signal will decrease
then increase to a higher level on the spectrum analyzer. The increased signal level
is the main signal beam.
•
Using this higher signal level repeat Step 2 through Step 4 to get the antenna
peaked to the maximum transponder signal level.
Figure 32. RF Pattern
Step 5. When using a linearly-polarized system always check the feed polarity. Rotate the
feed to the optimum polarization setting after the antenna has been peaked on the
satellite.
•
When receiving true vertical polarization the receive port at the rear of the feed
should be in the horizontal position (see Figure 33). This corresponds to 0
°
on an
angular scale relative to the feed support. In this configuration the antenna will
receive true vertical polarization and transmit horizontal polarization. To achieve the
opposite polarization, in both receive and transmit, the feed must be rotated 90
°
by
loosening the feed clamps and rotating the entire feed. This will correspond to 90
°
on an angular scale relative to the feed support.
•
In general, the incoming (Rx) /outgoing (Tx) signal polarization on the antenna will
not always be perpendicular or parallel to the Earth's surface. Because of this it will
be necessary to optimize polarization of the antenna feed by aligning it to the satellite
polarization. This is achieved by carefully rotating the feed until the feed and the
satellite are in the same polarization.