Comtech EF Data CDM-570A - Manual (Page 139)

CDM-570A/570AL Satellite Modem with Optional Packet Processor MN-CDM570A
Front Panel Operation Revision 2
6–35
If you wish to constrain the system to run at a fixed ModCod, set the Min and
Max ModCod values to be equal.
The value of Max ModCod may be limited by other FAST codes installed. For
example, suppose the 4100 ksps FAST option is installed, and the symbol rate
set to 4100 ksps, the theoretical maximum data rate would be 14 Mbps at
ModCod 11. However, if CnC is being used, with a 10 Mbps FAST limit the
ACM Max ModCod will be limited to ModCod 7, or 9.6 Mbps.
(CONFIG: TI) IP-ACM  Unlock-Action
Distant-end loses lock:
Go to Min Tx Modcod(▲ ▼)
Use this submenu to establish the desired action when the remote demod loses lock. This is
important, as the ACM system depends on the feedback of the SNR metric from the remote
demod to determine the optimum ModCod. Use the ▲▼ arrow keys to select Go to min Tx
ModCod (recommended) or Maintain Tx ModCod. Press ENTER.
(CONFIG: TI) IP-ACM  Target-SNR-Margin
Target SNR Margin:
1.0 dB (0.0 – 4.5) (▲ ▼)
Use the ▲▼ arrow keys to select a margin value from 0.0 to 4.5 dB, in 0.5 dB increments. Press
ENTER.
The ACM system is designed to switch based on thresholds that correspond to a
BER of 5 x 10 -8 for each ModCod. However, in order to prevent oscillation around
two ModCods at this exact value, 0.3 dB of hysteresis has been added.