Promax PROLINK-4C Manual De Instrucciones página 165

USER'S MANUAL. PROLINK-4C
The BER measurement is provided in scientific notation (i.e. 3.1 E-7 means
-7
3.1x10 , that is to say 3.1 wrong bits of each 10000000) and through a graphic bar (as
its length is smaller the signal quality will be better). The analogue representation is
done on a logarithmic scale (not linear), that is to say, the bar divisions correspond to
the exponent of the measurement.
With the aim to have a reference about the signal quality, it is considered that a
system has a good quality when it decodes less than one non-correctable error for
every transmission hour. This border is known as QEF (Quasi-Error-Free) and it
corresponds approximately to a BER after Viterbi of 2.0E-4 BER (2.0x10
2 wrong bits of each 10000). This value is marked on the measurement bar of the BER
and therefore, BER for acceptable signals must be at the left side of this mark.
In the lower line of the screen it appears the W. P. counter (Wrong Packets
counter). This counter shows the number of non-correctable packets received after
Reed-Solomon during the measuring time. This counter is automatically activated when
the unit detects an MPEG-2 signal.
If at any time, the received signal stops to satisfy the requirements of the
MPEG-2 standard, this counter will deactivate, that is to say it will keep the number of
non-correctable packets received and the measuring time, later, if an MPEG-2 signal is
received again, it will activate with no reset.
When during any measuring time interval the counter has been deactivated, in
other words the signal has not satisfied the MPEG-2 synchronism, the presentation of this
counter will alternate with another counter titled FAIL. This second counter shows the time
that the detected signal has not fulfilled the MPEG-2 standard requirements (12 seconds
in the example of the following figure) and the number of signal cuts (2 in the example of
the following figure). To reset the counter it is necessary to change any of the detection
parameters, for example tune again the signal or push twice the
Figure 16.- Signalling two MPEG-2 signal cuts with a total length of 12 seconds.
02/2003
-4
, that is to say
[22] key.
Page 45