Why Does The Hub Canceller Not Lock - Teledyne QMultiFlex-400 Installation And Operating Handbook

QMultiFlex-400™ Installation and Operating Handbook
Under the sub heading Manufacturing, is a Hardware Fitted list. This must contain 2x
DVBS2X Interface Cards, one which provides the Hub canceller functionality. In addition to
the Hardware, a software feature code is necessary (SAF). To verify whether or not you
have the SAF code to run the Hub Canceller feature, navigate to View > SAF menu. An
example is shown below:
Figure 8-21 - QMultiFlex-400™ Hub Modem SAF information
Under the Advanced Operation sub menu, check to see whether you have a Paired Carrier
SAF with a green On label associated with it. If you have then you should have access to
the feature. If there is a red Off label against it, then you don't. Under these circumstances,
please contact your distributor to purchase the necessary SAF code.

8.3.6.2 Why Does The Hub Canceller Not Lock?

The Hub canceller is a complex subsystem. It can take a while to commission it
successfully. By far the best way of bringing up the Hub Canceller is to first ensure it is
disabled and enable one of the inbound links at a time, then enable the outbound carrier
from the hub to all of the remotes. If any link fails to meet expectations in terms of
synchronisation, received signal level, signal to noise ratio, frequency offset etc. then it
won't meet expectations when the Hub Canceller is enabled. Once your links are
operational with the Hub Canceller disabled, you will be in a better position to diagnose any
issues that may exist when the Hub Canceller is enabled. Follow the steps listed in section
4 and onwards for further details on how to commission a Hub Canceller link and how to
configure the canceller's delay sweep parameters used as part of its acquisition process.
The commonest reasons for failure to lock are:
1. Configuration or Frequency Planning Error
Ensure the Hub Canceller delay or geo-coordinates are entered correctly. Check the Hub
Modem configuration and that the outbound carrier occupies the expected space segment
on satellite. Ensure the inbound carriers are all configured correctly in terms of frequency,
amplitude and that they are spaced sufficiently so as not to interfere with neighbouring
carriers. Check these carriers are in the correct space segment on satellite, drop the Hub
outbound carrier to facilitate this.
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