Constellation - Horizon Fitness HD-S2 User Manual

Constellation

Provided the meter is locked to a DVB-S QPSK, DVB-S2 QPSK / 8PSK / APSK or DSS modulated carrier
the constellation mode is available from the Sub-menu (press the UP button while the signal level or carrier/
noise display is on screen). If there is no lock, the option will be "greyed out". This type of diagram is almost
meaningless when it cannot display formatted data – as dots would appear randomly in each quadrant, and
there would be no visible pattern.
In the Sub-menu, scroll down to highlight "Constellation", and press the RIGHT arrow. The screen will
change to the QPSK constellation display and a listing of the current transponder settings.
The graphic displays the 4 quadrants of a QPSK signal. A "good" display will show a cluster of dots centred
in each quadrant. The more concentrated the cluster, the better the quality of the received signal; dots
"straying" from the cluster indicate noise on the signal, phase errors, and other unwanted artefacts.
The aim is to achieve the best result possible, which a thorough alignment of the LNB should achieve. With
the constellation diagram, you get reassurance that the adjustments have been done well.
At the right side of the screen is a list of the parameters for the currently chosen transponder:
Frequency in MHz: this is the measured frequency after "pull-in" by the meter's Automatic Frequency Control
(AFC), so the displayed value may differ slightly from the nominated value in the configuration file;
Symbol Rate in kilo Baud (Kilo Symbols / Second): the data rate is critical in identifying and locking to the
selected carrier;
FEC (forward error correction) value: data on the selected carrier will conform to one of a short list of
standard FEC values;
IQ Norm indicates that IQ Swap is not present. Pilots are shown if present.
Tip: The constellation diagram can be used down stream from the LNB to trace problems caused by faulty
components that introduce noise and affect the quality of the digital signal.
11840MHz
22000kBd
QPSK 5/6
IQ Norm
10758MHz
30000kBd
8PSK 2/3
IQ Norm
Pilots
10750MHz
30000kBd
16AP 2/3
IQ Norm
Pilots
32APSK Constellation display is also supported.
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This illustration shows how a typical
QPSK constellation diagram would
be represented.
This illustration shows how a typical
8PSK constellation diagram would
be represented.
This illustration shows how a typical
16APSK constellation diagram
would be represented.