Comtech EF Data CRS-500, Installation And Operational Manual

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CRS-500 1:N Redundancy System
Revision 4
Cables and Connections 5–29 MN-CRS-500
5.4 IF Cable Connections
5.4.1 IF Cabling Overview
For hub applications, there are two basic IF configurations – single transponder or multiple
transponders .
For a single transponder configuration , connect all modems to the same Up/Down Converter.
This configuration eliminates the need for an IF Switch Unit (ISU) because the CRS-500 mutes
(shuts off) the offline modem’s Tx IF carrier.
For a multiple transponder configuration , you may group and connect the modems in various
combinations to multiple transponders. This configuration requires the use of ISU.
For either configuration, once all CRS-500 1:N Redundancy System connections have been
made and proper system operation has been verified, you should then connect the user-provided
Up and Down Converters.
To prevent unintended signals from reaching the satellite, do not
connect the IF to any Up Converters until the CRS-500 1:N Redundancy
System is fully cabled and configured.
5.4.2 IF Cable Connections – Single Transponder (No ISU)
To prevent problems resulting from impedance mismatch, ensure that the
impedance for the modem’s cables and combiner are the same.
Figure 5-12 shows an example of a single transponder IF configuration (L-Band operation is
depicted in this example). Connect the user-provided IF cables. Do these steps:
1. Make your Transmit (Tx) IF Connections:
a. Connect the appropriate user-provided IF cables from each modem’s “Tx IF”
connector (BNC for 70/140 MHz, Type ‘N’ for L-Band) to a single user-provided
power combiner.
b. Connect the output of the power combiner to the user-provided Up converter.
2. Make your Receive (Rx) IF Connections:
a. Connect the appropriate user-provided cables from each modem’s “Rx IF”
connector (BNC for 70/140 MHz, Type ‘N’ for L-Band) to the output ports of a
single user-provided signal splitter.
b. Connect the input of the signal splitter to the output of the user-provided Down
Converter.
c. When a modem is taken offline, its Tx IF is automatically muted (shut down) by
the CRS-500.