Comtech EF Data CRS-311 - Manual (Page 61)

CRS-311 1:1 Redundancy Switch Revision 7
Cables and Connections MN/CRS311.IOM
3–13
3.2.6 IF Connections – User to CRS-281x Module to Modems
The CRS‐281x module connects the online modulator's Tx IF signal to your RF Up Converter. It
also passively splits the receive IF signal to provide both demodulators with the same IF signal
coming from the LNB, thus reducing switching time.
For 70/140MHz IF switching, the CDM‐Qx uses the CRS‐281 IF Switch Module with either 50Ω or
75Ω BNC connectors
The CRS‐281A IF Switch Module is intended for use with the CDM‐QxL for L‐Band with Type ‘N’
connectors. This model also switches all of the BUC and LNB interface signals that are
multiplexed onto the transmit and receive coaxial cables, including:
• Tx and Rx L‐Band signals
• 10 MHz reference to BUC and LNB
• DC Power to BUC and LNB
• FSK signaling to the BUC
To prevent problems resulting from an impedance mismatch, ensure that the
impedance for the modem’s cables and combiner are the same.
Referring to Figure 3‐7 and Figure 3‐8, connect and secure the IF cable pairs – PL/0946‐1 50Ω or
PL/0813‐4 75Ω Type ‘BNC’ or CA/RF10453‐4 Type ‘N’ – between your Up/Down Converters,
CRS‐311, and CDM‐Qx/QxL modems as follows:
Traffic Modem Connections:
• From the CDM‐Qx/QxL connector labeled “Rx”, to the CRS‐281x Switch Module
connector labeled “J1 Rx”, and
• From the CDM‐Qx/QxL connector labeled “Tx”, to the CRS‐281x Switch Module
connector labeled “J2 Tx”.
User Connections:
• From your Down Converter, to the CRS‐281x Switch Module connector labeled “J3 Rx”,
and
• From your Up Converter, to the CRS‐281x Switch Module connector labeled “J4 Tx”.