Can one purchase a fibre-optic or similar insulator
to isolate the input from a TV aerial?
The reason I'm looking for it is slightly complicated.
My aerial is shared with my neighbour,
who gets a microwave feed.
I used to get the same service,
until I turned to Sky,
and now I want just to get local stations directly.
e-mail (<80k only): tim /at/ birdsnest.maths.tcd.ie
There is a TV outlet in my house,
but when I connect a television to it
my neighbour's television is affected.
This is because it used to be part of a shared system,
at which time the feed went into a decoder box.
It seems to me that if I had an optical isolator
then connecting a TV could not affect my neighbour.
I believe it might allow local stations to be received.
I might add that I have a normal input
from a Sky aerial on my roof.
The input I am talking about is entirely separate,
and goes into an attic bedroom.
e-mail (<80k only): tim /at/ birdsnest.maths.tcd.ie
On Wed, 19 May 2004 00:02:27 +0100, Timothy Murphy
I don't think that you will find one at any price that you would be
willing to pay able to handle UHF TV signals (if at all).
The solution is a separate antenna or to find out what the source of
interference is. It is possible that your TV is being overloaded
with signal and is creating an interfering signal or that it has a
Is it possible that you neighbour's equipment is putting a power supply up
the cable and your equipment is d.c. coupled and loading it? A wall-mount
socket that is d.c. isolated (signal fed through a capacitor) may be all
that is needed.
OK, whatever you need it isn't an optical isolator - they are for much
lower frequencies and although the principle could (with difficulty)
be made to work for TV signals it isn't a sensible thing to do.
There are a number of types of signal that could be arriving at your
house and that of your neighbour through that socket, many of which
would end up not working if you simply plugged your TV into the
If you really want to use the socket you need first to find out
exactly what sort of signal it is.
Of all the options the simplest is that it could be a normal TV aerial
that doesn't have all that strong a signal on it and goes to both
sockets. Originally you would have needed some sort of signal booster
or signal splitter to allow it to feed two sets. It is quite likely
that if this is the case then at some point that device became faulty
and the neighbour just tried connecting his TV to the wall socket. As
long as there is only one TV connected this would work. As soon as
you connect your set you have 2 TVs in the circuit and it would no
longer work without the booster/splitter. The easy way to identify
this is to check if there is anything connected between the aerial
socket and either your neighbour's TV or video recorder - if the
aerial cable goes directly to one of these then try getting him to
unplug his aerial lead and have just your TV connected - if this works
you know what is required (but you may need someone that understands a
little about aerial wiring to ensure that the booster/splitter ends up
in the correct place).
The next option is that you have an aerial with a weak signal that is
boosted by an amplifier in the loft or somewhere else near the aerial.
The normal way to supply power to these is to send it up the same
cable as the TV signal coming back donw (yes you can send several
things through the same cable!). What you will find here is that your
TV may well be upsetting this power supply (as a previous poster said
it's DC-coupled) this is a very bad thing as not only will the booster
not work while your set is plugged in you may damage the power supply
for the booster by trying this (depending on how well designed it
is!). The easiest way to tell if this is the case is again to have a
look at the cabling behind your neighbours TV - rather than the cable
going directly from the wall to the TV or video it will go via a box
that is about the size of 2 cigarette packets or a video tape which
itself is plugged into a power socket. The solution for this problem
may well be simple!! The booster will probably give a good enough
signal that you can get away with connecting your set to your aerial
socket with an isolator with AC-coupling. Any decent TV shop will be
able to sell you one, just explain that you need it to allow you to
connect your TV to an aerial connector that also carries power for a
Alternatively the signal may come from a satellite or a cable TV
supply. If this is the case you won't be able to use it at all.
There are some other possibilities (such as a strange distribution
system for running a large block of flats from one aerial or sat/cable
decoder) but these are also not likely to be much use to you.
If either of the last two options seem to be what you have you will
probably need to experiment with an indoor aerial, fit a new aerial
for the bedroom, or get a splitter to allow you to run the signal from
your other TV to the bedroom.
I hope this is some help!!
P.S. When you say you have Sky aerial on the roof I assume you mean a
dish. If this is the case you could consider getting Sky to install
an extra decoder for you - this does cost 10 quid per month, but you
get all the extra channels.
I think the device you are after is an opto-isolator. We use them at work to
keep field wiring apart from the computers they feed into.
I would suggest asking the question in uk.tech.digital-tv as there are many
knowledgeable people in there.
It sounds like the OP has a downlead with both microwave and UHF on
it. The tuner in the TV might load the downlead excessively at
microwave frequencies, bit like plugging a normal phone into an ADSL
line without the filter :)
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