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USER’S MANUAL. TV EXPLORER II/II+
12/2013
Page
61
En
g
lis
h
There are different types of constellation diagrams for the different modulation
modes. With the
TV EXPLORER II / II+
it is possible to display constellations for
DVB-T/H
,
DVB-C
,
DVB-S
and
DVB-S2
signals.
In the case of an ideal trnasmission 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
Every modulation type is represented differently. A
DVB-C
16-QAM signal is
represented on the screen by a total of 64 different zones 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
DVB-T/H (COFDM) signal
Activate the
UTILITIES
menu by pressing the
[22] key, and select the
CONSTELLATION
option. Now, on screen will be recorded the hits due to symbols
received during the digital signal transmision.
MODULATION:
DVB-T/H (64 QAM)
F:
CH:
CARRIER:
TYPE: data
66
MHz
794.00
MPEG-2 TS DVB-T
CLEAR
ZOOM:x1
DECAY:
16
0
Figure 41.-
Constellation Diagram. DVB-T/H (
QAM 64
) signal.
By means of the rotary selector [1] and the arrow cursors
[6] key, is possible
to change the frequency, channel or
COFDM
carrier on tune by the instrument.
The
DECAY
option sets the visual persistence for symbol impacts on the screen in
a range from 0 (minimum persistence) to 16 (maximum persistence).
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