Q-Flex Satellite Modem Installation and Operating Handbook
6-69
Table 6-73
indicates the circumstances under which modem signal inversions are
required in relation to
Paired Carrier™
operation.
Paired
Carrier
Working?
BUC
LNB
Tx Modem
Inversion
Rx Modem
Inversion
Yes
Non Inverting
Non Inverting
No
No
Yes
Non Inverting
Inverting
No
Yes
Yes
Inverting
Inverting
No
No
No
Inverting
Non Inverting
N/A
N/A
Table 6-73 Paired Carrier™ Spectral Inversion Control
PLEASE READ THE FOLLOWING INFORMATION FOR FIRST-TIME
SETUP OF A PAIRED CARRIER
™
LINK.
In relation to
Paired Carrier™
,
generally there are no restrictions on how
the overlapped carriers are brought up and the satellite link is established.
However, the following guidelines may be useful in proving correct
Paired
Carrier™
operation as part of the overall initial link deployment process.
Once correct operation is established then
Paired Carrier™
can be
switched on and off or reconfigured just like any other modem feature.
You must get each link working correctly as a normal link prior to
switching Paired Carrier™ on! You must ensure that there is no spectral
inversion in the RF chain – if there is then this must be corrected by re-
inverting it for Paired Carrier™
operation to work – see the above table.
1. Ensure
Paired Carrier™
is switched off (via the
Paired Carrier enable
setting on the
Edit->Paired Carrier
menu).
2. Before starting, it is strongly recommended to prepare for a BER data
transparency test, using data test sets connected to each modem, or
using the modem internal PRBS BER test feature, which can be
temporarily enabled if necessary.
3. Configure both modems for identical services, including the same Tx
and Rx frequencies.
Different PRBS test patterns must be used in each direction (e.g. for
Modem 1 Tx to Modem 2 Rx use 2^15-1 and for Modem 2 Tx to Modem 1
Rx use 2^23-1). This ensures that the two signals are sufficiently
different from each other to allow Paired Carrier™ to work.
4. Check the Tx power level setting is correct and bring up the first carrier
(using the selected common transmission frequency) and
•
Check the receive signal level, Eb/No, spectrum and
constellation are as expected.
•
Check the received signal is data transparent.
5. Switch the first carrier off.
6. Check the Tx power level setting is correct and bring up the second
carrier (using the selected common transmission frequency) and