Atsc Signals - Promax TV EXPLORER HD ATSC Manual De Instrucciones

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 before FEC of 2.0E-4 BER (2.0x10
bits of every 10,000). This value is marked on the measurement bar of the BER and
therefore, BER for acceptable signals must be at the left side of this mark.
Below the BER analogue bar it is shown the tuned frequency (or channel) and the
frequency deviation in kHz between the tuned frequency and the one, which optimizes
the BER (i.e. 800.00 MHz + 1.2 kHz). This deviation must be adjusted specially from the
C/N measurement in satellite band, by tuning again the channel in frequency mode
[24], to the lower reachable value.
5.14.7.3

ATSC signals

Once determined the parameters of 8-VSB signal, it will be possible to measure
BER.
In a reception system of terrestrial digital signal, after the 8-VSB decoder two error
correction methods are applied. Obviously, each time we apply an error corrector to the
digital signal, the error rate changes, therefore if we measure the error rate at the output
of the 8-VSB demodulator, at the output of the Viterbi decoder, and at the output of the
Reed-Solomon decoder, we obtain nothing more than different error rates. The
TV EXPLORER HD
TUNER
Figure 36.- Screen of BER measurement 8-VSB signals. VBER
Page 58
ATSC provides the BER after Viterbi (VBER).
8-VSB
A/D
DEMOD.
Figure 35.- 8-VSB reception system.
USER'S MANUAL. TV EXPLORER
-4
, that is to say two incorrect
MER BER after Viterbi
VITERBI
HD ATSC
SER
REED-SOLOMON
12/2010