Comtech EF Data VMS v3.12.x Vipersat - Manual (Page 281)

Chapter 4 - Configuring Network Modems 4-63
MN/22156, rev 12 Devices
ACM Link Adaptation can be enabled for the VersaFEC return path between
the CDM-840 modulator and the CDD-880 demodulator (see section “Network
| WAN | ACM” on page 4-37).
Click in the ACM Enable check box to activate the feature.
Select the desired Target Es/N0 Margin (0.0–4.5 dB) from the drop-down
menu.
Because the switch points for the ACM feature can determine whether or not
ModCod oscillations occur, this is a very important parameter. Increasing
these switch points is recommended, for example, in an environment that
will experience fading. Adding sufficient margin will help to maintain
demod lock and adequate link quality.
Set the Maximum ModCod, based on the site link budget calculations.
Important: After setting the Maximum ModCod parameter for the CDM-
840, this same setting must be entered for the Remote Site for this unit:
• Under the ViperView Network Manager, right-click on the Remote Site
in the tree view and select Properties.
• Select the InBand Return Path ModCods menu item, as shown in
figure 4-40, and set the Default Parameters to match the ACM
Maximum ModCod for the unit.