Comtech EF Data CDM-625A, Installation And Operation Manual

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CDM-625A Advanced Satellite Modem MN-CDM625A
Front Panel Operation Revision 4
6–23
6.2.1.4 CONFIG: Rx
RxIF Freq FEC Demod Data Descram Eq EbNo
(Data 02048.000kbps,02184.533ksps) (  )
On the top line – Use the ◄ ► arrow keys to select a parameter. Press ENTER .
On the bottom line – Read-only Data/Symbol rate information is provided.
1) When CONFIG: Mode = IP-ACM or V2-ACM, EbNo on the top line of this display
is replaced by SNR.
2) When Sub-Mux is ON, the Data Rate information on the bottom line of this
display is replaced by Composite Rate information.
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 a parameter. Press ENTER .
•
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 you select
±
32 kHz with a data rate of 2.4 kbps, BPSK will result in an
average acquisition time of around 3 minutes.
The Rx symbol rate determines the Sweep Range limits:
Rx Symbol Rate Sweep Range Limit
±1 to symbol rate / 2 (ksps) 18-64 kbps
±1 to 32 kHz 64-389 ksps
±1 to (10% of symbol rate) 389-3000 ksps
±1 to 300 kHz >3000 ksps
Use the
▲▼
arrow keys to edit the setting in 10 kHz increments. Press ENTER .
• Spectrum Invert – Use the
▲▼
arrow keys to set Spectrum Invert as Off or On . Press
ENTER .
SPECTRUM INVERT should normally be in the OFF position. Rx spectrum is
inverted in the ON position (which is the same as reversing the direction of
phase rotation in the demodulator). When in BPSK mode, note that the