Config: Rx  Rx-If - Comtech EF Data CDM-625A Installation And Operation Manual

CDM-625A Advanced Satellite Modem
Front Panel Operation
6.2.1.4.1 CONFIG: Rx  Rx-IF
Rx: Acquisition Sweep Range = +/- 032 kHz
SpectrumInvert=Off Rxα=.35(.35,.12)()
Use the ◄ ► arrow keys to select Acquisition Sweep Range, SpectrumInvert, or Rxα (for Rx
Alpha Filter Rolloff Factor), and then press ENTER to continue.
• Acquisition Sweep Range: The Acquisition Sweep Range value 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) cause excessively long acquisition times. For example, when selecting ±32 kHz
with a data rate of 2.4 kbps, BPSK will result in an average acquisition time of around 3
minutes.
Use the
▲▼
The Rx symbol rate determines the Sweep Range limits:
Rx Symbol Rate
±1 to symbol rate / 2 (ksps)
±1 to 32 kHz
±1 to (10% of symbol rate)
±1 to 200 kHz
• Spectrum Invert: Use the
press ENTER.
•
Rxα (Rx Alpha Filter Rolloff Factor): Use the
value of 0.35, and then press ENTER.
arrow keys to edit the setting in 10 kHz increments, and then press ENTER.
arrow keys to set Spectrum Invert as Off or On, and then
▲▼
SPECTRUM INVERT should normally be in the OFF position. When in the ON
position, the Rx spectrum is inverted (which is the same as reversing the
direction of phase rotation in the demodulator). When in BPSK mode, note
that the demodulator will automatically synchronize to either the normal
time-ordering of bits FEC codeword pairs, or the inverted ordering used by
certain other manufacturers.
• If the Txα of the signal being received is 0.25 or 0.35, select Rxα = 0.35.
•
If the Txα of the signal being received is 0.20, 0.15, 0.10, or 0.05, select
Rxα = 0.12.
Sweep Range Limit
18 - 64 kbps
64 - 389 ksps
389 - 2000 ksps
>2000ksps
arrow keys to select 0.12 or the default
▲▼
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Revision 0
MN-CDM625A