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CDM-600 Satellite Modem Revision 7
Offset QPSK Operation MN/CDM600.IOM
8–2
The two consequences of this are:
1. Acquisition may be longer, especially at low data rates.
2. The acquisition threshold is higher than for normal QPSK, although the
demodulator will maintain lock down to its normal levels. For Firmware
Versions prior to 1.3.1, the acquisition thresholds are as follows:
7.0 dB Eb/No for Rate 1/2
5.2 dB Eb/No for Rate 3/4
4.8 dB Eb/No for Rate 7/8
4.0 dB Eb/No for Uncoded operation (No FEC)
Firmware Versions of 1.3.1, or higher, have improved these figures by
approximately 2-3 dB.