Pagina 74 - TELE-satellite-1205

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TELE-satellite International — The World‘s Largest Digital TV Trade Magazine
— 04-05/2012
Do Not Allow LTE Data
Transmissions To Interfere
With Your DVB-T/T2 Reception
3GPP LTE wireless high
speed data transmissions
for mobile phones and data
terminals may in some cir-
cumstances interfere with
regular terrestrial TV re-
ception. That’s because the
highest part of the classical
terrestrial TV range is to-
day dedicated for LTE rather
than DVB-T/T2. As digital TV
requires much less band-
width than analog TV to
transmit the same number
of TV channels, it became
possible to dedicate part of
its original frequency range
for high speed data trans-
missions. But because most
of the existing antenna in-
stallation pass the whole
frequency range up to 862
MHz, LTE signals may find
their way into your DVB-T/
T2 receiver’s input.
Despite the fact that LTE
data is transmitted in a dif-
ferent frequency range than
DVB-T/T2 terrestrial signals,
if they are strong enough
they can interfere with reg-
ular TV reception. If LTE
signals are strong and you
do not use any filter, some
intermodulation might take
place in your receiver’s de-
modulator. Spurious signals
created due to intermodu-
lation will manifest them-
selves as excessive noise
degrading the quality of the
LTE Filter
component is an amplifier,
a multiswitch, a receiver or
any equipment that requires
electric power to operate.
In simple installations with
no additional components,
you connect the filter any-
where between the antenna
and the receiver. Probably it
will be more practical to put
it next to the receiver. In
more complex installation,
the filter should be inserted
before the amplifier or the
multiswitch whatever hap-
pens first when looking from
the antenna side. One filter
should be enough for the
whole network if only your
signal distribution equip-
ment is well shielded and
the connectors are firmly at-
tached to coaxial cable ends.
If the antenna has a built-
in amplifier, you will have no
choice but to connect the
filter at the antenna output.
The results could be slightly
worse because LTE signals
will have the opportunity to
mix up with terrestrial TV
signals in the antenna am-
plifier and can intermodulate
one another. However, such
not desired intermodulation
should be minimal in well
designed amplifiers hav-
ing high dynamic range. So
even if you have an active
antenna with a built-in am-
desired signals. You can eas-
ily detect this with an analog
signal (unwanted additional
white/black dots and audio
noise). With a digital re-
ceiver you can detect it by
measuring signal quality.
If signal quality measured
by your receiver changes
over time, or worse your
receiver from time to time
looses completely the ability
to process video and audio,
one of possible causes can
be interference created by
LTE signals intermodulating
with your receiver’s input. It
is very easy to confirm such
hypothesis: just connect the
SMA 790 and observe if sig-
nal quality improves.
For the best results, the
SPAUN SMF 790 filter should
be placed before the first
active component of the re-
ception system. An active
SPAUN SMF 790 LTE Filter
Most effective way to block interference
from LTE (3G) mobile networks