On Sat, 09 Apr 2011 17:28:26 +0100, John Rumm
wrote:

On 09/04/2011 16:21, MM wrote:
That is, the cable from the back of the TV to the wall plate.

I need to watch the TV in the annexe which has no wall plate, so I
could run an extension from, say, the kitchen's wall plate. But what
is the limit to the length and would I need some sort of booster?

This is alas one of those "how long is a piece of string" questions. It
depends on how much signal you have and what quality it is. How much
your TV needs. And what quality of cable you are using to extend it.

All of which are unknowns.

So without any test equipment, the best you can do is try it and see.
Assuming the picture is good now, then dropping in another 15m of decent
quality foil screened co-ax is unlikely to degrade it much. If you
wanted 50m then that will make more difference.

The aerial is currently driving a 14"analogue (CRT) Sony portable, but
will soon be connected to an LCD TV.

And the LCD with probably have a digital tuner, which will open another
can of worms depending on the local reception conditions for digital
channels.

If you have a few minutes to spare, there is another question:

My house is equipped with a Philex SLx6 aerial amplifier in the loft.
This has 6 output sockets, of which only five are connected at present
(kitchen, bedroom 1, bedroom 2, bedroom 3, and living room).

Reception is excellent in four rooms, but in the living room the
picture was grainy. Not too bad, but definitely not as good as in any
of the other rooms, all supplied with the same type of wall outlet.

I have just spent an hour up in the loft tracing the cables from the
amplifier to the various rooms in order to isolate the one going to
the living room and causing the grainy picture. In the process of this
tracing I pulled the cable out from under the loft insulation as I
tracked along it so that I could expose the whole cable and check for
"funnies", like someone may have hit it with a chisel or something.

Then I connected my little portable once more to the living room wall
outlet, went back up into the loft and reconnected the suspect cable
to the amplifier.... Result: Perfect reception!

But why? What gives here? (I am no electrician, although I understand
the basics.) The cable is at present simply laying across the loft, on
top of the insulation (rock wool, not that that makes any difference).

In a nutshell:
Cable routed "neatly" alongside joists under insulation = poor
reception
Cable simply laid across the loft on top - good reception

This cable is very long. From the aerial amplifier to the wall outlet
downstairs it must be 15 metres, perhaps even 17.

I was expecting to have to pull the cable out of the conduit and
possibly replace it, but that now seems superfluous, since I don't
care if the cable simply lays there where it now is.

Any comments (from anyone) most welcome.

Thanks!

MM