Comtech EF Data CRS-200 - Manual (Page 37)

CRS-200 Redundancy Switch Setup Guide
Rev. 1 6–5
6.3 IF Cables And Transponder Switch
Next, the IF carriers of all the modems must be configured. There are two options as to
how these are to be handled. The transmit IF carriers from all the modems may be
combined and sent to a single upconverter, or each modem may be associated with its
own transponder. The setup for these two options are described next.
IMPORTANT NOTE
Comtech EFData does not supply IF cables or IF splitters/combiners with the CRS-200 Redundancy
Switch. It is the responsibility of the User to furnish these items.
6.3.1 Single Transponder
If all modems are to be connected to the same transponder, it is necessary at this time to
configure each modem’s transmit side to the proper data rate, IF frequency and output
power level. Once this is done, the user must combine these carriers together using BNC
cables into a single power combiner. The output of the combiner is then fed to the
upconverter. Both the cables and the combiner must be the same impedance as the
modems to prevent mismatch.
On the receive side, the output of the downconverter must be attached by BNC cables to
a single splitter which in turn feeds all the receive IF ports of the modems. When a traffic
modem is taken offline, its transmit IF will automatically shut down and be replaced by
that of the redundant modem so that no interference occurs.
6.3.2 Multiple Transponders Using Crs-280 Transponder Switch
If, on the other hand, each modem is to be connected to its own transponder, then the
system requires the Comtech CRS-280 Transponder Switch. This connects to the CRS-
200 with a 25-pin control cable. Transmit and receive BNC cables connect to the
modems in use. The CRS-200 automatically senses the presence of the CRS-280 so that
the CRS-200 will no longer suppress the transmit IF output of the offline modem (Tx
Traffic LED stays on). Instead, the Transponder Switch will switch the redundant
modem’s IF in place of the traffic modem being taken offline. This arrangement is shown
in Figure 5.