On Wed, 17 Jul 2013 18:08:49 +0100, RJH wrote:

On 07/06/2013 22:02, tony sayer wrote:
In article om, mick
scribeth thus
On Tue, 04 Jun 2013 20:40:24 -0700, Roy Brophy wrote:

I am running a Cat 5 cable close to a 6mm SWA cable over a 15M run.

Is it worth using shielded Cat 5?

It's supplying a garden studio so there will be the occasional
electric fire / kettle kicking in and out.

Roy


At 15m and if trenching allowed, I'd just bury some hosepipe a minimum
of 12" (preferably 24") away from the armoured & thread cat6 through
it. The pipe lets you pull another through if you need to (include a
draw wire!). You should be able to use gigabit ethernet over that -
something that wifi can only dream about. It's simpler and cheaper
than fibre. OTOH, if you can't allow that sort of spacing, then fibre
is really the only answer.


Why would you need to be 2 foot away from a cable thats very
effectively shielded?.

CAT 5 is a very good balanced transmission system and is inherently
good at rejecting other electric fields, so why so far away?..


I'm running some cat6 alongside mains cable in places - obviously, it's
the easiest route to follow through a house. I did read that it's not
advisable, but thought I'd give it a try and so far, so good. Do you
think that ethernet-next-to-mains-equals-disaster is an urban myth?

It's no urban myth. Although the signal down the network cable is
balanced, that balance can never be perfect. Interference from the mains
cable induces a 50Hz hum in the cat5 - which it can handle most of the
time. The problems tend to arise when you get spikes on the mains -
sometimes the result of dimmers etc. Those aren't always filtered out
completely. As the network is self-correcting it will keep asking for
packets to be repeated if they are corrupted. The overall result is that
the network slows down.

The more current is on the mains supply, and the worse the loads on it,
the more noise it will radiate. Consequently you'll find that in
distribution systems in buildings any data cables will be spaced well
away from power cables.

The risk from shock on the network system is as much as grabbing hold of
the (insulated) mains cable.