Atsc Signals - Promax US TV EXPLORER II Manual De Uso

USER'S MANUAL. US TV EXPLORER
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
US TV EXPLORER II provides the BER after Viterbi (VBER).
TUNER A/D
-7
FREQ:
CH:
MPEG-2
Figure 36.- Screen of BER measurement 8-VSB signals. VBER
The BER measurement is provided in scientific notation (i.e. 3.1 E-7 means
-7
3.1x10 , that is to say 3.1 average value of wrong bits of each 10000000) and through
a graphic bar (as its length is smaller the signal quality will be better). The analogue
representation is done on a logarithmic scale (not linear), that is to say, the bar divisions
correspond to the exponent of the measurement.
The BER measurement shown by default (when PRN-23 BER option from
Preferences menu is set to OFF) yields an estimated value calculated using the MER
measurement. In order to obtain a more accurate BER measurement value, the PRN-23
BER option from Preferences menu must be set to ON and a PRN-23 signal pattern
must be used through the RF signal input [30].
11/2013
II
MER
8-VSB
DEMOD.
Figure 35.- 8-VSB reception system.
-6 -5 TOV
57.00 MHz C/N:
-3 kHz POWER:
A02 MER:
SER:
» VBER:
BER after Viterbi
VITERBI REED-SOLOMON
-3 -2 -1
>21.3 dB
55.8 dBµV
19.5 dB
1.0E-5
1.0E-8
SER
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