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www.TELE-satellite.com —
09-10/2012 —
TELE-satellite International —
全球发行量最大的数字电视杂志
tenuated before reaching
the FibreIRS ODU32.
Except for the satellite
signal, the FibreIRS ODU32
accepts also a signal from
DTT/DAB/FM
antennas.
Preferably, the latter one
should come not directly
from terrestrial antennas
but through a DTT proces-
sor of Global Invacom de-
scribed in the previous issue
of TELE-satellite (Pages 16-
21 in TELE-satellite 06-07-
08/2012). In this way, we
can achieve the best possi-
ble performance. FibreIRS
ODU32 has two optical out-
puts as well as a connector
for 20V DC power supply.
GlobalInvacom provides a
suitable plug type power
supply unit. You do not need
a separate power supply
unit for the LNBm. It gets
DC power via the thick coax
cable from the ODU 32.
But the picture is not com-
plete yet. Two optical chan-
nels have to be distributed
among a number of end us-
ers. To do that, you can use
optical splitters like Spit2-
OFpro or Split4-OF – 2 way
or 4 way optical splitters
offered by GlobalInvacom.
At the very end of such sys-
tem, a device called FibreM-
DU should be connected.
The FibreMDU converts the
optical signal back to the
RF domain. It has four out-
puts. So, up to four regular
satellite receivers can be
connected to it and each of
them will be able to receive
any channel from the satel-
lite the dish is directed to.
No matter which sub band
or polarity. That’s because
everything comes down
through the fiber optic ca-
bles to FibreMDU.
We started our tests with
measuring the optical split-
ters. Spli2-OFpro specifica-
tion promises not more than
4 dB attenuation of the sig-
nal (from the input to any of
its two outputs). We meas-
ured that the actual attenu-
ation was only 3.5 dB. The
same story repeated for
Split4-OFpro. Its actual per-
formance was better than
its specifications (6 dB vs.
7 dB). This is the way good
manufacturers specify their
products. Once they prom-
ise something, they deliver
it! It is not a universal rule
these days unfortunately.
We are happy to say that
you can trust GlobalInva-
com.
Then, we decided to test
the whole system. First, we
measured a classical system
with a very good low noise
LNB installed on a 90 cm
offset dish to have a refer-
ence for the optical system.
Our reference system had
about 20 meters of coax-
ial cable. The problem was
which satellite we should
use? A very strong one in
our location - like ASTRA
19.2° East or HOTBIRD 13°
East or rather a weaker one
like TURKSAT 42° East. We
decided to make it hard for
GlobalInvacom and chose
TURKSAT. Some of its tran-
sponders are actually below
the reception threshold of
most contemporary receiv-
ers. Fortunately, our satel-
lite analyzer – SPAROS SAT
HD of SPAUN is an extreme-
TELE-satellite Test Editor
Jacek Pawlowski testing
a setup with rolls of fibre
optic cable imitating a large
distribution system.