Comtech EF Data SDM-9000, Installation And Operation Manual

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SDM-9000 Satellite Modem Configuration
Rev.4 3–9
3.5 Nyquist Filter Configuration
The Nyquist filter (AS/4124) is a 4.5” x 5.0” daughter card that is located on the
modulator and demodulator PCBs. The filters are capable of supporting four data/code
rate and modulation type combinations per card. There is one TX card and one RX card:
Type Part Number Used with
TX PCB AS/4124-1 Baseband Modulator PCB (AS/3969)
RX PCB AS/4124-2 Baseband Demodulator PCB (AS/3970)
The filters include a factory programmable device that contains:
•
Data Rates
•
Coding Rates
•
Symbol Rates
•
Options
This information is programmed into the filter PCB at calibration time. A label indicates
the symbol rates of the populated filters. For example, a Nyquist filter may be required
with four symbol rates as follows:
•
21.376 MHz
•
22.912 MHz
•
29.824 MHz
•
34.560 MHz
Configuration information is recovered from the filter PCBs during system power-up and
initialization. The filter configuration information is available to the user. Refer to
Chapter 4 for the Configuration Modulator, Configuration Demodulator, and Utility
menus.