Comtech EF Data CDM-550T Manual page 90

Offset Qpsk Operation
The demodulator must re-align the I and Q symbol streams before the process of carrier
recovery can take place. For various reasons this makes the process of acquisition more
difficult. 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. The acquisition thresholds are as
follows:
8–2
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)
CDM-550T Satellite Modem
Rev. 1.3