Re: Re: CAT-5 wiring details

[Nigel Orr <Nigel.Orr@xxxxxxx>]

At 08:15 28/09/00 +0000, you wrote:
>Thanks. How near is nearby?

About as long as a piece of string ( ie it depends on transmitter power,
frequency, antenna directivity, local propagation conditions, orientation
of the cables in the house, absorption by walls, [phase of the moon, your
choice of lottery numbers etc etc]).

A house I rented once was 100m from one of the main MW transmitters in the
area, which taught me more than I ever wanted to know about reducing
interference pickup in electronics... pick up the phone, you heard the
radio, plug a mic lead into a preamp, it picked up the radio, plug a 'scope
probe in and up popped the demodulated RF... I think the only place I
didn't get it was in my fillings!

>I am about 2 miles from the Wrekin
>TV transmitter. Is this likely to cause me any problems?

Probably not.  Though it is a big one- 100kW.  Do you notice interference
from it currently on anything?  You could try a few 'worst case' cable runs
and see what happens before putting any of it under the floor.  I suspect
it will be fine though.  If you were within a couple of hundred metres of
it, it would be more likely a problem.  Audio and Video links, being the
'most analogue', are probably the most likely to be noticably affected, IR,
phones and security sensors shouldn't have a problem, ethernet might
conceivably if you were closer.

To be honest, I find balancing and differential drives are much more
effective at rejecting interference than screening, unless the noise source
is _very_ close (less than a few cable diameters, at which point the 2
wires in twisted pairs don't behave as if they are colinear any more), so
it's probably fine to wire it all in UTP and then add drivers (KATV!)
if/when you find you need them (and Keith finds time to make them!)

Nigel


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