Promax TV EXPLORER HD+ Manual De Instrucciones página 202

It is a very useful measurement in order to analyse systems in which signals of
different types and sources interfere among them, as in the case of the transition from
analogue to digital TV.
In next figure a MER by carrier analysis for a COFDM 8k signal is performed.
As it shows in the following figure, when analysing MER by carrier in this digital
channel appears three degradation areas throughout the channel that make suspect the
presence of an underneath analogue channel.
Analog level
Video Carrier
MER by carrier
Figure 55.- Scheme of interference due to TV analogue signal over a digital channel.
If we compare this graphic with the spectrum analyser of an analogue channel we
realise that in effect the video, audio and colour carriers affect more intensively the MER
of those digital multiplex located at the same frequencies. In this case, the COFDM
channel is strong enough to be affected by this interference.
This interference could not be detected in any other way for it can't be seen on the
spectrum analyser and it is not strong enough to degrade the average MER, CBER or
VBER readings substantially.
Page 78
Figure 54.- MER by carrier function.
Frequency
Colour Audio
Subcarrier Subcarrier
Carrier
USER'S MANUAL. TV EXPLORER HD+
MER
by carrier
Carrier
11/2013