Comtech EF Data CDM-425, Installation And Operation Manual

Page: 131 / 744

CDM-425 Advanced Satellite Modem
Revision 0
Front Panel Operation 6–13 MN-CDM-425
Tx
α (Tx Alpha Filter Rolloff Factor) – Use the ▲▼ arrow keys to select the Txα. Press
ENTER .
Valid settings are:
Txα (Tx Alpha Rollout Factor) (%) Default
0.05, 0.10, 0.15, 0.25 0.35
The Rx
α of the corresponding receiver must match the Txα – see Sect.
6.2.1.4.1 for details. To summarize:
•
Set Rx
α = 0.35 if Txα ≥ 0.25
•
Set Rx
α = 0.12 if Txα ≤ 0.20
6.2.1.3.2 CONFIG: Tx

Freq (Frequency)
Tx-IF Frequency: 0070.0000 MHz
(

)
To edit the Tx-IF Frequency, use
the ◄ ►arrow keys to select a digit, and then use the ▲▼
arrow keys to change that digit. Press ENTER. Valid settings are:
IF Frequency Range Step Size (Increment)
70/140 MHz 50-180 MHz 100 Hz
L-Band (FAST Option) 950-2250 MHz 100 Hz
When you use the ODU menus to configure a BUC lockout frequency, this screen displays a
second line of information:
Tx-IF Frequency: 1750.0000 MHz
(LO:12500 MHz Sat:14250.0000 MHz) (

)
As you edit the IF frequency, the Satellite frequency updates accordingly.
Satellite frequency = LO ± IF frequency
,
where the sign ± is determined by the LO mix parameter:
•
High-sided mix [–] (includes a spectral inversion);
•
Low-sided mix [+].