Comtech EF Data DT-4500 Series - Manual (Page 99)

81
Appendix C.
Theory of Operation
Applications 81
RF Signal Conversion 82
Monitor & Control 84
Installation, Operation and Maintenance 84
C.1 A
PPLICATIONS
This appendix contains a general description of the theory of operation for the Model DT-
4500 Series Down Converters. The DT-4500 Series Down Converters are used for
SCPC, DAMA AND TDMA, as well as for full transponder HDTV and analog TV,
applications.
The converter operates over the RF frequency range with a typical gain of 35 dB. The
RF output level is +10 dBm at 1 dB compression allowing the capability for longer cable
runs to compensate for splitting networks without adding options such as external line
amplifiers.
The phase noise performance exceeds the Intelsat phase noise mask for IBS and IDR
services by more than 9 dB. This allows high capacity earth stations to add more
demodulators and still meet transmission standards. The close-in phase noise is also very
low make the converter ideal for low bit rate digital circuits such as used in DAMA hub
earth stations.
A selectable RS-232C or RS-485 remote control serial communications connector
interface is provided on the rear of the converter. All configuration control, status
retrieval and adjustments are available as ASCII commands through the serial interface,
or as local operator input command to the converter.
A detachable Input/Output Module (IOM) can be mounted in the rear of the converter
chassis for switching the RF output for single thread operations, or for testing the output
of the unit. The connectors for the IOM are located on the rear panel.
In applications where converters are "Daisy Chained" together to provide distributed on-
line protection switching to a backup Converter, the IOM is replaced with a detachable
Transmit Switch Module (TSM). The TSM contains RF and IF transfer switches. Type
N connectors are provided for the RF loop, and 50 or 75 ohms BNC connectors are
provided for the IF loop.