Fracarro SIG7120 Instrucciones De Uso página 31

Constellation: QPSK
Guard Interval
1/4
1/2 4.976
2/3 6.637
3/4 7.464
5/6 8.294
7/8 8.706
The various COFDM modulation parameters (number of carriers, constellation, FEC, guard interval) can be set
by the installer to make the system more efficient in critical installation conditions (for example lack of spurious,
several adjacent channels, transmission with errors,...).
IMPORTANT: in standard installation diagrams, we recommend keeping the COFDM modulation settings with
the default values (64-QAM constellation, 7/8 FEC, 1/32 guard interval). How you can see in the tables above,
the default settings guarantee a wider bandwidth.
The modulator programming must be done in order to make it as insensitive as possible to an increase of a
bitrate of one or more programs inserted queue in the output multiplex. The multiplex of the output programs
is organized according to a Last In First Out priority: the last inserted program in the queue is the first program
to be removed if it exceeds the maximum available bitrate threshold. The program's position in the list can be
modified at any moment through the proper TPE menu.
In the event of an overflow alarm, the module continues operating correctly by eliminating one or more programs,
starting with the one that has a lower priority (the first inserted program is the most protected one).
NOTE: carry out a complete reset of the output channel list before inserting other channels.
It is fundamental to distinguish the programming into two typologies according to the transmission mode of
the programs to be distributed, which means in the case of a transmission with a static bitrate (A) or a dynamic
bitrate (B). We recommend referring to the statistics provided by web sources before, alternatively (but this
solution may not be sufficient), monitoring the bitrate measurements provided by the TPE for a few minutes.
A. In the event of channels transmitted with static bitrate (generally channels with standard definition - SD),
programming should be done as follows:
1. reset the bitrate peaks from the TPE menu,
2. check the setting of the modulation parameters,
3. insert the programs in the output multiplex one at a time by inserting the measurement reading of the used
bitrate;
4. after inserting all the desired programs, make sure that the measurement of the used bitrate peak (available
from the TPE MEASUREMENTS menu) does not exceed the maximum available limit.
IMPORTANT: pay attention not to exceed the threshold of the maximum bitrate that varies according to the set
modulation parameters according to the tables shown before. In the event that the overflow event takes place,
the red LED in the front panel of the module flashes rapidly and an alarm FLAG is set in the TPE. This alarm can
be displayed and reset from the MEASUREMENTS menu of the programmer. Furthermore, one or
1/8 1/16 1/32
5.528 5.855 6.032
7.372 7.807 8.043
8.294 8.782 9.050
9.216 9.756 10.053
9.674 10.246 10.554
Constellation: 64QAM
1/4
1/2 14.928 16.589 17.564 18.093
2/3 19.905 22.118 23.416 24.126
3/4 22.393 24.881 26.346 27.143
5/6 24.881 27.647 29.272 30.161
7/8 26.123 29.027 30.737 31.669
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2/3
3/4
5/6
7/8
Guard Interval
1/8 1/16
31
Constellation: 16QAM
Guard Interval
1/4 1/8 1/16
9.952 11.057 11.711 12.064
13.271 14.745 15.612 16.086
14.928 16.589 17.564 18.093
16.589 18.430 19.516 20.104
17.416 19.352 20.490 21.114
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programs