Televes DVB-S2 COFDM, User Manual

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DVBS2 - COFDM
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In short, the higher and further to the left the DVB-
T mode selected is, the more powerful this mode
will be in terms of information service output
(Mbits/sg).
On the other hand, the lower and further to the
right the DVB- T mode selected is, the more robust
this mode will be in terms of interferences which
could aff ect the signal.
The terrestrial transmission channel (transmission
aerial - terrestrial atmosphere – receiving aerial) is
very complex, with numerous interferences that
can potentially aff ect the DVB-T signal.
Due to this, in Spain, the DVB- T signal is generally
disseminated with the following features:
(1) Type of modulation: 64QAM
(2) Level of protection against Errors: 2/3
(3) Level of protection against echoes: 1/4
If one looks at the previous chart, one can see that
the information service output of the DVB-T mode
is 19.91 Mbits/sg.
In our case, the DVB-T signal generated by the
DVBS2-COFDM transmodulator, Ref. 563101, is not
going to be transmitted through the terrestrial
transmission channel, but through a channel that
is generally much more benign: the distribution
network of the building.
NOTE: The better the quality of the building´s
distribution network, the better the transmission
channel will be when transmitting signals.
Given that our transmission channel is better,
we can use the DVBS2-COFDM transmodulator,
Ref. 563101, by selecting a higher DVB-T output
mode than that used by terrestrial channels to
disseminate. This will have a greater information
service output (Mbits/sg) and will therefore enable
us to include a greater number of TV and Radio
services.
Therefore, when setting up the DVBS2- COFDM
transmodulators, Ref. 563101, one should follow a
procedure such as the one below:
1 - Select one of the stronger DVB-T output
modes.
E.g. 64QAM-5/6 with GI=1/32, information
service output of 30.16 Mbits/sg.
2 - Check the quality of the signal received at
various points within the building.
If the signal quality is good, the technician can
consider using an even stronger DVB-T mode,
in other words, one with a greater information
service output. On the other hand, in cases where
the signal quality is insuffi
cient, they must consider
using a more robust DVB-T mode.
In most cases, the distribution network within
the building should support those DVB-T modes
that have a lower protection level against echoes.
Therefore, if a more robust mode is necessary,
one should fi rst try using, one at a time, greater
protection levels against errors.