USER’S MANUAL. PRODIG-5
Page 52 11/2006
3) Enter the parameters relative to the digital signal which appear in the
measurement CONFIGURATION menu, as described previously.
4) Select the option to exit from measurements CONFIGURATION menu.
5.14.5.1 DVB-C signals
Once determined the parameters of QAM signal, it will be possible to measure
BER, press the
[12] key until the BER measurement display appears.
In the BER measurement mode, the monitor will show a display like the following
one:
-6 -5 -4 -3 -2 -1
FREQ:
CH:
MPEG-2
650.00 MHz
-3 kHz
C/N:
POWER:
MER:
» BER:
dB
dBµV
dB
16.5
66.2
24.7
3.4E-4
43
Figure 26.- Screen of BER measurement of QAM signals.
The BER measurement before error correction is shown: BER before FEC
(Forward Error Correction).
In a digital reception system for cable signals, after the QAM demodulator an
error correction method called Reed-Solomon is applied (see following Figure).
Obviously, the error rate after the corrector is lower to the error rate at the QAM
decoder output. This is the reason because this screen provides the BER measurement
before FEC (Forward Error Correction).
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