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P300H P300 Series Modem Installation and Operating Handbook Page 72
Spectrum Invert [?]
1=Normal 2=Invert
Change, Tx/Rx, Spectrum Invert Menu
AUPC: 1:Mode 2:Max 3:Min 4:Slew rate
5:Target Eb/No 6:Tolerence 7:Loss act'
Change, Tx, Modulator, AUPC Menu
6.6.16 Change, Tx/Rx, Modulator, SPECTRUM INVERT Menu
This menu allows the Tx Spectrum to be inverted, to cope with satellites or frequency conversion equipment
which also inverts the spectrum. Note that apart from the fact that the modem will not lock onto an
inverted spectrum, on a spectrum analyser the carrier is to all appearances unchanged.
The operator is warned if SPECTRUM INVERT is active when SETUP-CHECK is requested.
NOTE ON BPSK SPECTRUM INVERSION
True spectrum inversion does not affect BPSK signals and so in BPSK mode there is no requirement for
a true spectrum invert feature. Instead in BPSK mode (to be compatible with other manufacturers
equipment), the Tx Spectrum Invert option reverses the ordering of the pairs of Tx data symbols from the
FEC encoder to the modulator. The `Normal` option is compatible with other manufacturers BPSK
equipment. The Invert option (ie reverse pairs of Tx symbols) is compatible with earlier Paradise products
such as the P200 (which we consider to have the `correct` symbol pairing !). On the Rx path the symbol
pairing is automatically determined, and so the Rx Spectrum Invert feature has no effect in BPSK.
If interworking with other manufacturers equipment it is worth reading the notes in the section “Interworking
different manufacturers equipment” on page 153 which covers primarily scrambling, but also the
requirements for Spectrum Invert with Viterbi/Sequential in BPSK and QPSK.
6.6.17 Change, Tx, Modulator, AUPC (Software >=V2.12)
This menu is only displayed if the AUPC feature is available. It is advisable to refer to the introduction to
AUPC in section 8.11.1 on page 154 before enabling this facility.
Note that options 2 through 7 only display when the AUPC mode It is set to other than Off or Monitor
Distant, so initially only “AUPC: 1:Mode” may be displayed.