USER’S MANUAL. TV EXPLORER II/II+
Page 56
12/2013
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
-4
, that is to say 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.
TPS in lock
The TPS (
Transmission Parameter Signalling
) are decoded. The TPS are carriers
(17 in the 2k system and 68 in the 8k system) modulated in DBPSK, containing
information related to the transmission, modulation and codification: Modulation
type (QPSK, 16-QAM, 64-QAM), Hierarchy, Guard Interval, Viterbi Code Rate,
Transmission mode (2k or 8k) and Number of the received frame.
MPEG-2 TS DVB-T
Correct detection of a DVB-T signal, the demodulator provides a TS MPEG-2.
MPEG-2 TS DVB-H
Correct detection of a DVB-H signal, the demodulator provides a TS MPEG-2.
5.14.7.3
DVB-S/S2 signals
Once determined the parameters of
QPSK
signal, it will be possible to measure
BER
. Following is shown the
BER measurement
before the error corrections
:
BER
before the FEC
:
CBER
.
