Constellation Diagram - Promax TV EXPLORER HD+ Manual De Instrucciones

MER represents the relation between the average power of DVB signal and the
average power of noise present in the constellation of the signals.
When measuring MER, it also shows the noise margin in DVB-T, DVB-T2, C, S
and the Link margin in DVB-S2, which indicates the distance from the QEF point at the
current signal.
By example, QAM 64 demodulators require a MER greater than 23 dB to work.
Though it is preferable to have at least a 3 or 4 dB margin to compensate for any
possible degradation of the system. While QAM 256 demodulators require a MER
greater than 28 dB with margins of al least 3 dB. Normally, the maximum MER value
seen in portable analysers is of approximately 34 dB.
Finally it is shown a status line, which displays information about the detected
signal.
5.15

Constellation Diagram

The constellation diagram is a graphic representation, of the digital symbols
received over a period of time.
There are different types of constellation diagrams for the different modulation
modes. With the TV EXPLORER
DVB-T/H, DVB-T2, DVB-C, DVB-S and DVB-S2 signals.
In the case of an ideal transmission channel, free of noise and interferences, all
symbols are recognised by the demodulator without mistakes. In this case, they are
represented in the constellation diagram as well defined points hitting in the same area
forming a clear dot.
Noise and impairments cause the demodulator to not always read the symbols
correctly. In this case the hits disperse and create different shapes that at the end will
allow to determine at a glance the type of noise in the signal
Each type of modulation is represented in a different way. A 16-QAM signal is
represented on screen by a total of 16 different zones and a 64-QAM is represented by a
diagram of 64 different areas and so on.
The constellation shows in different colours the density of hits and includes
zooming, scrolling and clearing functions for a better graph representation on screen.
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USER'S MANUAL. TV EXPLORER HD+
HD+ it is possible to display constellations for
11/2013