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USER'S MANUAL. PROLINK-4
Before measuring the BER or analysing the Wrong Packets in the Transport
Stream MPEG-2 / DVB is necessary to define some parameters concerning the digital
signal, which are described in the following section (see section '4.9.1.5.1. Measuring
BER of QAM Digital Channels (QAM)'). To see its present value or to modify it, being in
the BER measuring screen, press the rotary selector, it will appear a multiple-choice
menu showing the functions relative to the BER measurement on the screen.
Once set-up the necessary parameters for tuning and measuring the digital
signals, depending on used modulation type, the PROLINK-4 offers the possibility of
visualizing the decoded digital TV images (see section '4.9.3 Decoding MPEG-2 / DVB
Channels, access to Digital Services').
4.9.1.5.1
Measuring BER of QAM Digital Channels (QAM)
Press the rotary selector to access the QAM signals parameters that must be
defined by user and that are described below:
1)
Modulations
It defines the modulation type. When selecting this function and pressing the
rotary selector a multiple-choice menu will appear on the screen, this menu
permits to choose one of the following modulations: 16, 32, 64, 128 and 256.
2)
Symbol Rate
When selecting this function and pressing the rotary selector a multiple-choice
menu will appear on the screen, this menu permits to choose one of the
following values: 6900, 6875, 6111, 5000, 4443, 1528, 1500, 1408, 1333, 1266,
1000 kbauds, or well to define any other value by means of the Other option.
When selecting the Other option, a screen titled QAM SYMBOL RATE will appear,
this screen shows present Symbol Rate value, to modify it press key
enter the new value (four figures) and finally press the rotary selector to activate it.
3)
Spectral Inv.
If necessary, activate the Spectral inversion. If the spectral inversion is not
correctly selected, reception will not be correct.
4)
Attenuator
It permits to select attenuation between 0 and 30 dB. It is advisable to activate
the 30 dB attenuator under that measurement conditions where the signal level
is near to the maximum input level (approximately starting from 20 dB under the
maximum level) and it is possible that the tuner becomes saturated. Under no-
saturation conditions, when increasing the attenuation value the BER measure
must to maintain or to increase (insufficient signal level) but never to decrease.
Once you have defined the QAM signal parameters, it will be possible to
measure the BER.
02/2003
[31],
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