Constellation Diagram; Itu-T J.83/B (Qam-Annex B) Signal - Promax TV EXPLORER HD ATSC Manual De Instrucciones

5.15

Constellation Diagram

The constellation diagram is a graphic representation, of the digital symbols
recived over a period of time.
There are different types of constellation diagrams for the different modulation
modes. With the TV EXPLORER
ATSC, 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.
5.15.1

ITU-T J.83/B (QAM-Annex B) signal

Go to the UTILITIES menu by pressing the
CONSTELLATION option.
For example the modulation type: ITU-T J.83/B is showed on screen. Next, the
frequency and channel number corresponding to the channel plan.
Figure 45.- Constellation Diagram. MPEG-2 TS ITU-T J.83/B.
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USER'S MANUAL. TV EXPLORER
HD ATSC it is possible to display constellations for
[22] key, and then select the
HD ATSC
12/2010