Comtech EF Data CDM-550T Manual page 80

Forward Error Correction Options
However, if uncoded operation is used, there is no way to recognize a data false lock. The
demodulator will indicate that it is correctly locked, but the data out will not be correct.
CAUTION
As an example, if 64 kbps QPSK uncoded is used, the symbol rate will be half of this
rate, or 32 ksymbols/second. One quarter of this equals 8 kHz. Therefore, the absolute
maximum acquisition sweep range which should be considered is +/- 8kHz. If there is
any frequency uncertainty on the incoming carrier, this should be subtracted from the
sweep width. The problem becomes progressively better with increasing symbol rate.
COMTECH EF DATA CANNOT BE HELD RESPONSIBLE FOR INCORRECT
OPERATION IF THE USER DOES NOT ADHERE TO THESE GUIDELINES WHEN
USING UNCODED OPERATION.
7–8
Comtech EF Data strongly cautions users when using uncoded operation.
If the acquisition sweep width exceeds one quarter of the symbol rate, there
is a very high probability that the demodulator will false lock.
CDM-550T Satellite Modem
Rev. 1.3