Pagina 18 - TELE-satellite-1207

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TELE-satellite International — The World‘s Largest Digital TV Trade Magazine
— 06-07-08/2012
A Set of Brick
Wall Filters
and Signal
Fibre Optic System for DTT
FibreIRS DTT Processor
Delivery perfectly clean DTT signals for any
distribution system
GlobalInvacom is a leading
company in introducing fiber
optics to satellite tv recep-
tion and TV distribution net-
works. Now they introduced
another very useful piece of
distribution system that can
be very beneficial not only
for fiber optics based sys-
tems but also for classical
coaxial cable systems.
GlobalInvacom’s DTT Pro-
cessor is a device installed
between a terrestrial anten-
na and the remaining part
of a distribution system.
Its most important function
is filtering the signal your
antenna picks up. Filter-
ing means passing through
the desired part of the fre-
quency spectrum where
the signals of interests are
transmitted while blocking
everything else from reach-
ing the output.
Why is this that impor-
tant? Thanks to the filtering,
the signal that finally comes
to the input of your DVB-T or
DAB receiver contains much
less noise. The probability
of picture pixelation, video/
audio glitches or complete
loss of reception is greatly
reduced. Starting with a
clean signal is even more
important in a distribution
system based on fiber optic
components. That’s because
we need to convert the elec-
trical RF signal existing in
the initial stages of such
system to modulated light.
GlobalInvacom’s converter
capable of changing electri-
cal currents into light will be
covered in our next test re-
port. Such converter if fed
with very a noisy input sig-
nal might have a problem in
generating well modulated
light. Typically, the rule is:
garbage in = garbage out.
If the signal quality is low
at the input, it will become
even worse at the output.
Fortunately, filtering can be
used to break this rule.
The FibreIRS DTT Pro-
cessor of GlobalInvacom
accepts signals from two
terrestrial antennas: one re-
ceiving terrestrial TV signals
and the other digital audio
(DAB) signals. The output is
one. That’s because DVB-T
TV operates in the 470-862
MHz range while DAB in the
217-230 MHz range. So it is
possible to combine them in
one RF output.
The basic version of the
DTT Processor enables you
to select up to six different
TV channels. You can buy
additional plug-in modules
and extend its functional-
ity to eight DVB-T channels.
Each channel is 8 MHz wide
in accordance with a typical
terrestrial DVB-T-TV chan-
nel plan. Consequently, the
DAB band is treated as one
13 MHz wide channel.
We are used nowadays
that one needs to connect
a notebook PC to configure
a professional system unit.
It is convenient when the
settings we need to do are
complex. But in the case of a
DTT processor, the settings
are quite simple: the num-
ber of a channel you want
to be passed through and
its signal gain. So it is really