Digital Tv: Measuring Mer - Promax US TV EXPLORER 2 User Manual

Viterbi synchronized
A digital carrier has been detected and the Viterbi algorithm is synchronized, but
too many frames arrive with non correctable errors. It is not possible to quantify
the BER.
MPEG-2
Correct detection of a MPEG-2 signal.

5.14.8 Digital TV: Measuring MER

Once determined the suitable parameters for 8-VSB, QAM Annex-B or
QPSK/8QPSK signal reception, it will be possible to measure MER, press
until it appears the MER measurement screen.
0
FREQ:
CH:
MPEG-2
Figure 41.- Screen of MER measurement of ATSC (8-VSB) signals.
First of all, you will see the modulation error ratio measurement: MER.
Following, it appears the Noise Margin (NM) measurement (in the figure value 8.4
dB). It indicates a safety available margin according to the MER level measured that
allows signal degradation until arriving to the TOV (Threshold of Visibility) limit value.
Analogue and digital carriers are very different in terms of signal contents and
power distribution over the channel. They, therefore, need to be measured differently.
The modulation error ratio (MER), used in digital systems is similar to the Signal/Noise
(S/N) ratio in analogue systems.
The MER represents the relation between the average power of ATSC signal and
the average power of noise present in the constellation of the signals.
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USER'S MANUAL. US TV EXPLORER II
NM: 8.4 dB
10 20 30
57.00 MHz C/N: >21.3
-3 kHz POWER: 55.8
A02 » MER: 19.5
SER: 1.0E-5
VBER: 1.0E-8
[12] key
40
dB
dBµV
dB
10/2007