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QMultiFlex-400™ Installation and Operating Handbook
broadcast carrier to provide minimal degradation to the broadcast carrier reception at the
remote terminals. Therefore, the remote terminals do not require their own canceller.
In this section, by way of example, the hub Out-Bound (OB) carrier is sized as follows:
DVB-S2X, 8PSK, 23/36, Normal Frame, no Pilots, 10% roll-off, 10Msps (18.961734Mbps),
occupied BW = 10.998MHz. The modem QEF Es/No for this MODCOD is 6.4dB. The hub
carrier was arbitrarily placed at an IF of 140MHz.
The In-Bound (IB) carriers, of which there are five, are all sized as follows: DVB-S2, QPSK,
3/5, Normal Frame, no Pilots, 10% roll-off, 2Mb/s (1.683071Msps), occupied BW =
1.851041MHz. The modem QEF Es/No for this MODCOD is 4.1dB. The five IB carriers are
placed at the following IF's: 136MHz, 138MHz 140MHz, 142MHz and 144MHz. This places
all the IB carriers within the OB carrier BW.
In the example in this section, the In-Bound carriers are wholly contained within the Hub
Out-Bound carrier. However, the system can equally operate with the Inbound carriers not
being wholly contained within the Outbound carrier. i.e. The IB carriers collectively require
more BW than the OB carrier.
The Hub Canceller must be able to receive its own uplink signal, i.e. it doesn't work with
cross-strap transponders. The Link budget analysis will determine link configuration and
estimated overall savings of power and bandwidth with the Hub Canceller enabled.
Figure 8-6 QMultiFlex-400™ Hub Canceller System Diagram
8.3.1
HUB Hardware Configuration
Check within the 'Hardware fitted' information box (View > Unit) that the QMultiFlex-400™
series hub Modem has 2x DVB-S2X interface cards installed. With the Hub canceller
enabled the unit will support up to 14 demodulators, assuming all are enabled within the
feature list.
8-6
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