Promax HD Ranger +, User Manual

Page: 71 / 224

December 2014
7-63
7 TOOLS
7.1 Constellation
7.1.1 Description
The constellation diagram is a graphic representation of the digital symbols
received over a period of time. There are different types of constellation
diagrams according to the modulation type.
In the case of an ideal transmission channel without noise or interference, all
symbols are recognized by the demodulator without errors. In this case, they
are represented in the constellation diagram as well defined points hitting in
the same area forming a very concentrated dot.
Noise and interferences cause the demodulator to not always read the symbols
correctly. In this case hits are dispersed and create different forms which can
visually determine the type of problem in the signal.
Each type of modulation is represented differently. A 16-QAM signal is shown
on screen by a diagram of a total of 16 different zones and a 64-QAM signal is
represented by a diagram of 64 different zones and so on.
The constellation diagram shows in different colours the density of hits and
includes features to zoom, move and delete the display on screen.
7.1.2 Operation
The constellation is available to all DIGITAL signals, both TERRESTRIAL and
SATELLITE .
To access the CONSTELLATION tool:
Connect the RF input signal to the equipment.
Tune to a digital signal from satellite or terrestrial band.
Press the key (Tools).
Select CONSTELLATION .
The CONSTELLATION of the tuned signal appears.