Comtech EF Data CRS-500, Инструкция по установке и эксплуатации

Страница: 91 / 220

CRS-500 1:N Redundancy System
Revision 4
Cables and Connections 5–31 MN-CRS-500
5.4.3 IF Cable Connections – Multiple Transponders (Using ISU)
When Traffic Modems use multiple transponders, the CRS-500’s CRS-280/280L ISU provides
routing, control and isolation of all the modems’ IF signals – all Traffic and Redundant Modem IF
signals are routed through the ISUs.
Because relays on the CRS-280/280L ISU isolate any unwanted signals, non-faulted modems are
always connected to the correct up/down converters (transponders); furthermore, as the CRS-
500 automatically senses the presence of a CRS-280/280L ISU, the offline modem’s Tx IF
remains on.
Each ISU is available as a separate unit by bandwidth, accommodating either 70/140 MHz Band
or L-Band operation. Each ISU has a modular design permits different ISU combinations as
needed to cover multiple transponders operating either on the same IF-Band or on different IF-
Bands.
The table provided under Section 5.1.1.3 IF Switch Unit (ISU) Configurations lists the available
ISU and the pertinent CEFD IF cables. Figures in the sections that follow show 1:N IF cable
connections between Redundant and Traffic Modems and select CRS-280/280L ISU. Cabling
requirements are dependent on the ISU in each configuration.
5.4.3.1 Same Band (Tx/Rx)
One CRS-280/280L is required for all Traffic Modems in the CRS-500 1:N Redundancy System.
Figure 5-13 shows an example of a 70/140 MHz IF-Band same band / multiple transponder Tx/Rx
configuration with a 1:N redundancy setup, using a CRS-280 ISU and CDM-625/A modems.
Figure 5-14 shows an example of an L-Band same band / multiple transponder Tx/Rx
configuration with a 1:N redundancy setup, using a CRS-280L ISU and CDM-625/A modems.
Modem-to-ISU IF Cable
There are two cables per interface, one for Tx and the other for Rx.
•
For 75/140 MHz, 50 ohms, use cable PL/0946-2 (BNC
→ BNC, 8’)
•
For 75/140 MHz, 75 ohms, use cable PL/0813-8 (BNC
→ BNC, 8’)
•
For L-Band, 500 ohms, use cable CA/RF10453-
8 (Type ‘N’ → ‘N’, 8’)