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User manual
INTRODUCTION
Once the digital terrestrial TV (DTT) is being
broadcasted
in
a
modulation
COFDM, different from the one employed
for satellite and cable, the user must use a
specific receiver (COFDM IRD) to have
access to these new services.
This inconvenience could be solved distribu-
ting the COFDM signal by means of a
COFDM to PAL converter. In this way the
same TV set could be employed to receive
the analogue and the new digital programs,
and the user wouldn't have to buy a new
IRD. But with this method, transmodulating
to an analogue format (PAL), the quality and
the added value services that are offered by
the DTT are lost.
On the other hand the DVB project appro-
ved the ETS300473 norm, which establishes
the QAM modulation format as one of the
formats to distribute digital signals in
SMATV networks, due to the good beha-
viour against the noise and mismatches and
its very high spectral efficiency. In this way,
the digital satellite TV signals are being dis-
tributed in SMATV networks using QPSK-
QAM transmodulators, converting the sate-
llite modulation, QPSK, to QAM format.
DESCRIPTION OF THE PRODUCT
This format conversion method can also be
format,
used to distribute DTT signals in SMATV
networks.
The digital transmodulator COFDM-QAM
ref. 5056 allows the distribution in the
SMATV networks of the new services offe-
red by the DTT (video and audio high qua-
lity, subtitling, different languages, interacti-
vity...). And for the reception, it could be
employed the same QAM IRD used to watch
the transmodulated digital satellite signals.
The COFDM-QAM transmodulator ref. 5056
receives a digital terrestrial channel in
COFDM format, it demodulates this signal
obtaining a MPEG2 transport stream. Then
this MPEG2 transport stream is modulated
in QAM format and converted to RF output
channel using a agile up-converter. The dif-
ferent parameters to configure the COFDM-
QAM (input channel, output channel and
modulation format, mainly) are programmed
using the universal programming unit (ref.
7234).
The COFDM-QAM transmodulator ref. 5056
also allows the preamplifiers powering
through its input. The user can choose bet-
ween no powering, 12V or 24V.
The mechanics of the COFDM-QAM device,
T05, permits the perfect integration with the
rest of the T-05 series range as modulators,
digital and analogue channel processors,
modulators and transmodulators (QPSK-
PAL, COFDM-PAL and QPSK-QAM).
Finally this new transmodulator, has also the
RS485 interface, which will allow its integra-
tion in the headend management system in
the future.
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COFDM-QAM
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