Config: Interface Qdi; Config: Ref - Comtech EF Data CDM-Qx Installation And Operation Manual

CDM-Qx/QxL Multi-Channel Satellite Modem with DoubleTalk™ Carrier-in-Carrier®
Front Panel Operation
When
beyond Channel 6. Use right arrow key
pressed once the selection is made.
CONFIG: Interface
Port#X Line Code:
HDB3
Select HDB3 or AMI using the
HDB3
AMI
CONFIG: Interface
Port#X Bipolar Violation:
Active
Select Active or Masked using the
Masked (i.e., no alarm is generated).
5.4.7

CONFIG: Ref

The modem can accept an externally supplied frequency reference via the REF BNC connector
on the rear panel. However, rather than bypassing the internal reference and substituting the
external signal, the internal reference is used in a low-bandwidth (~2Hz) phase-locked loop
(PLL), so the modem actually phase locks to the reference external signal. There are two distinct
advantages to this scheme:
a. It permits hitless switching between the operation of internal and external reference.
There are no sudden discontinuities of frequency and phase in the transmitted carrier.
b. Due to the very low bandwidth of the PLL, it permits the external reference to have an
inferior phase noise characteristic than the internal reference of the modem. The narrow
loop essentially 'cleans up' the external signal. This is particularly important if the
modem is being used to supply a 10MHz reference to a BUC or LNB.
Edit the configuration and value of the frequency reference using the
when done. Available selections are as follows:
ENTER
•
Internal 10 MHz
•
External 01 MHz
•
External 02 MHz
•
External 05 MHz
Two configuration examples are as follows:
Frequency Reference:
Internal 10 MHz
Frequency Reference:
External 05 MHz
displays, as per this example, this means that there are more channels available
QDI
AMI
Selects High Density Bipolar Three Zeros Substitution line coding.
Selects Alternate Mark Inversion line coding
QDI
Masked
(▲ ▼,ENT)
(▲ ▼,ENT)
to view more, making sure that
1, 2, 3, or 4
(◄ ► ENT)
arrow keys, then press
1, 2, 3, or 4
(◄ ► ENT)
arrow keys, then press
• External 10 MHz
• External 20 MHz
• Out Int. 10 MHz
• Auto
5–36
Revision 7
MN/CDMQX.IOM
ENTER
LineCode
.
ENTER
Alarm
. The default is
ENTER
arrow keys. Press
is