SDM-300L3 Satellite Modem
Revision 1
Forward Error Correction Options
MN/SDM300L3.IOM
7–6
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.
