Constellation Diagram - Kathrein MSK 115 Betriebsanleitung

CONSTELLATION DIAGRAM

When the measuring instrument has locked on to a DVB-QPSK-modulated carrier, "Constellation" mode is
available via the sub-menu (press the UP button whilst the signal level or carrier-to-noise ratio is displayed).
If no lock-on has been achieved, this option remains greyed out.
Scroll down the sub-menu until "Constellation" is highlighted, then press the RIGHT button. The display will
switch over and will show the QPSK constellation and a list of the current transponder settings.
The graphical display shows the four quadrants of the QPSK signal. A "good" display displays an
agglomeration of dots near the outer corner of each quadrant. The more concentrated the agglomeration,
the better the quality of the signal being received; if dots are scattered outside the agglomeration, these
indicate interference on the signal, phase errors or other undesirable artefacts.
The objective is to achieve the best possible result; this can be achieved by careful alignment of the LNB.
The constellation diagram gives confi rmation that the signal setting is good.
On the right side of the display, a list of the parameters of the currently selected transponder is displayed:
Frequency in MHz: This is the measured frequency after "Synchronisation" by the automatic frequency
regulation of the measuring instrument. This means that the displayed value can easily vary from the value
set in the confi guration fi le;
Symbol rate in kBaud (kSamples/second): The data rate is critical for identifi cation and locking on to the
selected carrier;
FEC (Forward Error Correction) value: Data for the selected carrier match with a value from the short list
of standard FEC values;
IQ Standard shows that the IQ conforms to this and has not been swapped.
The state of charge of the battery pack is shown at the bottom right.
Tip:
The constellation diagram can be used to trace defective components that underlie LNB
problems, cause malfunctions and compromise the quality of the digital signal.
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OPERATING MENU
This diagram displays how a typical QPSK constellation diagram
appears.