Comtech EF Data CDM-IP 300L - Manual (Page 306)

CDM-IP 300L IP-Centric Satellite Modem Rev. 1
CD/CDMIP300L.IOM
280
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
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.
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
± 8 kHz. 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.
CAUTION
Comtech EF Data is not responsible for incorrect operation if the user
does not adhere to these guidelines when using uncoded operation.