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- Analyse the measures :
Signal level
-
V
: represents the received signal level
- VLNB : LNB supply voltage
(13V =vertical polarisation and 18 V = horizontal polarisation)
-
C/N
: means carrier/noise ratio
- ILNB : LNB supply current
Thanks to different colours, a threshold system enables seeing the signal quality easily. On the display digital values and bargraphs
appear.
The thresholds are set up according to reference values. For an digital signal, the transponder measures have to correspond to the next
data.
For a digital signal, the V and C/N measures don’t guarantee the signal quality by themselves. It is imperative to measure the error
rates (BER/MER) to fully characterise the reception quality.
Error rates
To operate the error rate measurements :
Press for the second time the « Measurements » key:
A new window appears on the display : « DVB-S : BER/MER ».
DVB-S : BER/MER window
- Analyse the measures :
The BER (Bit Error Ratio) et MER (Modulation Error Ratio) measures are very important to qualify a DVB-S digital signal.
- CBER : error rate before the Viterbi correction ;
- VBER : error rate after the Viterbi correction ;
- UNC : lost packet number after the Reed Salomon decoder ;
- MER : modulation error rate ( generally equivalent to the C/N measure).
The bargraphs appears in colour according to the measures error :
Signal level at the antenna plug
47dBμV <
V
< 77dBμV
Signal / noise ratio
DVB-S standard :
C/N
> 11dB
Transponder
characteristics
Error ratio
measure
VBER > à 2E-4
(QEF : quasi error free)
Without lost packets
Lost packets (UNC)
Correct error rate
Minimum
threshold
Maximum
threshold
