Promax 26 Mode D'emploi page 89

USER'S MANUAL. PROMAX-26
Figure 10.- Measurement functions menu (ANALYSE).
The template will show the measurements obtained according to the activated
work mode (registered or not registered) for both, the upstream and downstream. For
example, in the previous figure, working in not registered mode on downstream link the
following data appear: channel power 72 dbuV, MER 34 dB, tuning frequency 254.50
MHz in channel S14 which belongs to the CCIR active channel plan. The channel
bandwitdh (BW) is 7.00 MHz and the modulation (MOD) is 64 QAM with a symbol rate
(SR) of 2560 ksym/s. The BER recorded is below 1.0E-8.
a) QAM CONSTELLATION - IQ
Once the power channel and BER & MER measurements are obtained, the
Constellation Diagram graph can be obtained for DVB-QAM digital signals, (see
appendix B ' Principle of QAM digital modulation. Constellation Diagram').
After few seconds the PROMAX-26 shows a screen like the following figure.
This screen features the constellation diagram, the QAM modulation type, the symbol
rate (SR), the bit error rate
measured (see Appendix G 'Measurement the modulation error ratio (MER) for digital
channels') and the IQ quadrants represented (in this case, corresponds to four
quadrants "ALL").
In the display lower margin appears which quadrant is represented (in this case
is showed a graphical representation based on four quadrants, i.e. "ALL").
02/2007
(BER) generated, the modulation error ratio (MER)
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