Promax TV EXPLORER II Manual De Instrucciones página 168

In a digital reception system for satellite signals (DVB-S2), after the QPSK
decoder other two different correction methods are applied (see following Figure). In this
case, as the previous one, each time we apply an error corrector to a digital signal, the
error rate changes, therefore if we measure in a digital satellite television system, for
example, the error rate at the output of the QPSK/8PSK demodulator, at the output of
the Low Density Parity Check (LDPC) decoder, and at the output of the BCH decoder,
we obtain nothing more than different error rates. This is the reason because the BER
measurement is provided after LDPC (LBER). Also stating the Packet Error Ratio (PER)
as packets non-correctable received by the demodulator during the measurement
elapsed time.
Figure 37.- Digital reception system via satellite. (DVB-S2)
PER: 0
FREQ:
DL-Ku:
CH:
MPEG-2 TS
Figure 38.- DVB-S2 (QPSK/8PSK) signals LBER measurement screen.
The BER measurement is provided in scientific notation (i.e. 2.0 E-3 means
-3
2.0x10 , that is to say two incorrect bits of every 1,000) and through an analogue bar (as
its length is smaller the signal quality will be better). The analogue representation is done
on a logarithmic scale (not linear).
With the aim to have a reference about the signal quality, it is considered that a
system has a good quality when it decodes less than one non-correctable error for every
transmission hour. This border is known as QEF (Quasi-Error-Free) and it corresponds
approximately to a BER after Viterbi of 2.0E-4 BER (2.0x10
the measurement bar of the BER after Viterbi and therefore, BER for acceptable signals
must be at the left side of this mark.
Next it is shown the tuning frequency and the frequency deviation in MHz between
the tuned frequency and the one, which optimizes the BER (i.e. Freq: 1777.0
+ 1.2 MHz).
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USER'S MANUAL. TV EXPLORER II/II+
ELAPSED TIME: 00:00:05
2121.97 MHz C/N:
-1657 kHz POWER:
12722.0 MHz MER:
119 CBER:
» L BER:
16.1 dB
69.8 dBµV
12.6 dB
1.1E-1
2.7E-7
-4
). This value is marked on
12/2013