Promax PRODIG-3 Manual Del Usaurio página 122

Figure 26.- Screen of BER measurement (COFDM signals). VBER.
The BER measurement is provided in scientific notation (i.e. 3.1 E-7 means
-7
3.1x10 , that is to say 3.1 average value of 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.
Finally it is shown a status line with information about the detected signal. The
possible messages that can appear and its meaning are showing the following list. The
messages are exposed from less to more fulfilment of the MPEG-2 standard:
No signal received
No signal has been detected.
Timing recovered
Only it is possible to recuperate the symbol time.
AFC in lock
The system automatic frequency control can identify and lock a digital
transmission (TDT) but its parameters can not be obtained. It can be due to a
transitory situation previous to the TPS identification (Transmission Parameter
Signalling) or well to a TDT transmission with an insufficient C/N ratio.
Page 46
-7 -6 -5 QEF
FREQ: 650.00 MHz
-3 kHz
CH: 43
MPEG-2
USER'S MANUAL. PRODIG-3
-3 -2 -1
C/N: >21.3 dB
POWER: 55.8 dBµV
MER: 19.5 dB
CBER: 5.0E-4
» VBER:
5.3E-5
-4
, that is to say
03/2008