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QMultiFlex-400™ Installation and Operating Handbook
Degradation position 2: Hub individual stream MODCOD changes and reduces throughput
as necessary to maintain link (other streams stay the same). The remote transmit adjusts
MODCOD to keep the respective demodulator in lock.
Note: VCM can be used in the one-way outbound mode, but for maximum robustness the
bi-directional ACM would be typical in a multiple stream scenario.
8.2.2
Configuring ACM
To use the ACM function, the following procedure should be followed:
1. Prior to switching on ACM, configure the modems at all link sites at the highest
modulation order & code rate allowable (typically based on link budget). Ensure the
satellite link is operating correctly. If VCM is being used, then set up the streams
for the remote modems first and ensure stable operation for each stream.
2. Decide on a one-way or bi-directional scheme. It is possible only one side needs to
adjust to maintain the link in normal operation.
3. Set the remote modem Stream IDs to coincide with the HUB demod. The 'Edit->
IP->Advanced' menu contains the stream ID setting. i.e. Remote 1 feeds back info
to demod 1, Remote 2 to Demod 2 and so on...
4. Set the hub and remote modems to the desired ACM setting in the IP page; 'On' or
'Monitor'.
5. Review the remote Eb/No to confirm that it is being maintained correctly under
different atmospheric conditions. The web user interface status screen and ACM
graphs can be used to monitor performance.
8-4
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