Comtech EF Data VMS v3.12.x Vipersat - Manual (Page 407)

Appendix B - Antenna Visibility B-5
MN/22156, rev 12 Using Antenna Visibility
Example — Blocking Spectrum Affected by Local Ground
Frequency Interference
In the example shown here, Antenna Visibility is used to block off a portion of a
bandwidth pool at a given remote site due to ground interference on the lower
part of the transponder spectrum.
In this case, assume there is ground interference on the lower end of the tran-
sponder that overlaps into the bandwidth pool, as illustrated in the figure below.
Figure B-6 VMS Bandwidth Pool with Ground Interference
Note that the satellite spectrum view provided by the VMS, as shown here,
displays the transmit (uplink) carriers from the Hub and the remote sites. The
corresponding receive (downlink) carriers are determined by the frequency
offsets but are not visible.
This interference at the remote site may not affect the transmission path, but
could prevent reception in the lower portion of the pool. With no antenna visi-
bility block, the VMS would perform a switch with this remote, resulting in the
carriers being placed as shown below. This places the corresponding receive
carrier within the ground interference frequency range, and could cause a
disruption in communications.
Figure B-7 Transmit Carriers, No Visibility Block