Promax US TV EXPLORER 2 User Manual página 65

USER'S MANUAL. US TV EXPLORER II
TUNER A/D
Figure 32.- 8-VSB reception system.
-7
FREQ:
CH:
MPEG-2
Figure 33.- Screen of VBER measurement (8-VSB signals).
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].
If the input signal is like PRN-23 or a video signal, the BER and VBER
measurement are considered as acceptable when BER/VBER ≤ 3*10E-6 and SER-
ERR/s ≤ 2 being SER value the number of wrong packets taken as reference
measurement.
A signal is considered acceptable when SER-ERR/s ≥ 20 dB. This border is know
as TOV (Threshold Of Visibility) and it corresponds to an error rate after Viterbi of
3.0*10E-6 and a MER of 15 dB. This value is marked on the measurement bar of the
SER and therefore, SER for acceptable signals must be at the left side of this mark.
10/2007
MER BER after Viterbi
8-VSB
VITERBI
DEMOD.
-6 -5 TOV -3 -2
57.00 MHz C/N: >21.3
-3 kHz POWER: 55.8
A02 MER: 19.5
SER:
» VBER:
SER
REED-SOLOMON
-1
dB
dBµV
dB
1.0E-5
1.0E-8
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