Comtech EF Data CDM-550T Manual page 47

CDM-550T Satellite Modem
(CONFIG, RX) ACQ (Acquisition sweep range)
Rev. 1.3
(CONFIG, RX, FEC, RATE) FEC RATE (TURBO ONLY)
RX TURBO: 3/4(Q) 21/44(B)
5/16(B) 3/4(OQ) (ENTER)
Select Rate 3/4 (QPSK), Rate 21/44 (BPSK ONLY) Rate 5/16 (BPSK ONLY) ,
or Rate 3/4 (OQPSK) decoding rate, using the LEFT/RIGHT arrow keys, then
press ENTER. Note that OQPSK is a new feature added in S/W Version 1.19.
(For further details, see Section 7 - 'FEC Options'.)
EDIT RX ACQ SWEEP RANGE:
+/- 25 kHz (PRESS ENTER)
Edit the acquisition sweep range of the demodulator. This is accomplished by
selecting the digit to be edited, using the LEFT/RIGHT arrow keys). The value of
the digit is then changed using the UP/DOWN arrow keys. The user should then
press ENTER.
The range varies from +/- 1 kHz to +/- 30 kHz.
The value entered here determines the amount of frequency uncertainty the
demodulator will sweep over in order to find and lock to an incoming carrier.
When operating at low bit rates, large values of sweep range (compared to the
data rate) will cause excessively long acquisition times. For example: selecting
+/- 30 kHz with a data rate of 2.4 kbps, BPSK, will result in an average
acquisition time of around 5 minutes.
Front Panel Operation
6–17