SEFRAM 7805B Manuel D'utilisation page 26

3 - BER/MER (Bit Error Rate)
Please do first:
−
Recall a setup previously saved in a table of
parameters.
Refer to « Parameters »
−
Or choose directly a frequency, in this case the
standard will be QSPK, a high band or a low band, a V
or H polarization as well as a symbol rate corresponding to a transponder (choose first the
band and then the frequency).
In DVB-S and DSS coding, there are 2 successive correction algorithms: Viterbi and Reed
Solomon.
The instrument shows the following measures:
−
Bit Error Rate before Viterbi (on the main display). The typical value is 1.0
means that the error is corrected when 10,000 bits are received.
−
VBER (Viterbi Bit Error Rate) : Error Rate after Viterbi
−
UNC (UNCorrected packets): Error Rate after both Viterbi and Reed Solomon. This rate
corresponds to the packets uncorrected by the 2 successive correction algorithms. For
correct signal, the value must be 0.
−
MER (Modulation Error Ratio): it is similar to the C/N measure and is a good indicator of
the quality of the signal. A value up to 12.0 dB is ideal.
If the words « Sync ? » appear on the display, that means that there is no signal or that the
signal is not locked.
The sign « < » written in front of an Error Rate value means that there has been no error detected
yet.
In DVB-S2 coding there are 2 successive correction
algorithms :
LDPC (Low Density Parity Check)
BCH (Bose Chauhuri Houquenohem).
UNC becomes PER (Packet Error Rate)
In DVB-S2 mode, the power consumption is higher. To guarantee accurate
measurement, the working time should be half of the stand-by time and should
never exceed 20 minutes.
Example: a working period of 15 minutes in DVB-S2 should be followed by 30
minutes stand-by.
– 7805B –
p. 26
E
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