Figure G-15. Configuration | Test Page - Comtech EF Data CDM-760 Installation And Operation Manual

Appendix G
CDM-760 Advanced High-Speed Trunking Modem
Similarly, The Rx ModCod and Local Es/No graph on the read-only Status | Performance |
RxGraph page (Figure G-14, right) logs two pieces of data in time synchronous manner:
•
The left side of the graph has a vertical key of Rx ModCod (blue).
•
The right side of the graph has a vertical key of Local Es/No (red).
The Local Es/No is the Es/No of the local modem. When more than one ModCod is received in
the smallest interval period allowable by the graph, the most common ModCod received in that
time interval is displayed.
In this format, the graph depicts changes in ModCod that occur when the reported Remote
Es/No meets the Es/No trigger points to switch up or down.
Note that the Remote Es/No is the "reported" Es/No of the far end modem as seen by the local
modem. This reported Remote Es/No data can be 250ms to 400ms old as this is the amount of
time it can take for this data to traverse the satellite link for processing by the local modem.
Via Internal BERT Tester: When using the Ethernet IP interface, it is not an easy matter to verify
BER performance. A way to verify that the ACM link is meeting performance is by using the
internal BERT tester provided on the Configuration | Test page (Figure G-15). Not only will the
internal BERT verify BER performance, it is also tolerant of the change in bit rate that
accompanies a change in ModCod. The BERT can be used to confirm that there are no sync
losses or bursts of bit errors when a ModCod changes.
See Chapter 6. FRONT PANEL OPERATION for information about the Test Mode
configuration parameters available on this page:
Web Page Section
Unit
BERT Config
BERT Monitor
The Status | Performance | IQMon page (Figure G-16) provides you with a Constellation /
Spectrum Analyzer feature. If you have access to a bench oscilloscope in X-Y mode, Pins #3 and
#11 on the CDM-760 rear panel J1 | ALARMS connector provide analog voltages to monitor the
constellation. The advantage here is that ModCod changes may be viewed instantaneously.
Chapter 6 Section Reference
6.2.4.1 (TEST:) Mode
6.2.4.2 (TEST:) BERT  Off/On,  Patt
6.2.4.2 (TEST:) BERT  ErrIns,  Restart

Figure G-15. Configuration | Test Page

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