Televes COFDM-PAL, Руководство пользователя

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42
User manual COFDM-PAL
g.- Modulation Parameters
By pressing the button, you enter the
following menu that displays the detected
COFDM
modulation parameters . The digit
on the far left indicates the number of
carriers (8K - 2K). The following menu
displays the constellation (QPSK, 16 QAM
or 64 QAM) according to this table:
4 => QPSK
1 => 16 QAM
6 => 64 QAM
The following digit indicates the guard
interval according to this table:
4 => 1 / 4
8 => 1 / 8
1 => 1 / 16
3 => 1 / 32
The digit that can be found furthest to the
right indicates the Viterbi code rate, using
the following table:
1 => 1 / 2
2 => 2 / 3
3 => 3 / 4
5 => 5 / 6
7 => 7 / 8
“0” will appear as the selected audio and it
will be impossible to carry out any changes.
If the service selected does not dispose of
an audio channel, the following message will
appear on the display:
As is the case for the program selection, this
change takes place immediately but it is not
saved.
f.- CBER
By pressing the button, the CBER
reading or the bit errar rate before Viterbi is
displayed. Since this is only a reading menu,
neither the button nor the and
buttons are in use. The first three digits
correspond to the mantis and the third
corresponds to the exponent. For example:
This indicates an error rate of 2.5 x 10
-4
. A
signal with a typical C/N of around 12 dB
should correspond to an error measurement
of approximately 10
-4
, the minimum for an
acceptable reception being around 10
-2
.
When the demodulator is not linked, this will
be displayed: “9.9-0”.
d.- Program selection
By pressing the button, it is possible to
have access to the program selection , for
example program 5:
The and buttons allow us to select
the desired program between 1 and the
number of available programs in the
multi-
plex . This change takes place inmediately
but it is not saved in the memory.
If it has not been possible to process the
selected service, the following message will
appear on the display:
e.- Audio channel
By pressing the button, the selected
audio channel is displayed, for example
channel 1:
It is possible to select the desired audio
from those available in this service by using
the and buttons. If this service does
not dispose of any audio channel, the figure