Shielded CAT5 questions

Roady

Roady

Roady

Soldato
Joined
18 Oct 2002
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Hereford
Hi guys, I've been running CAT5 in businesses and homes for a while but I have an installation question (before we do something really wrong!)

We have been rolling out a fibre WAN install over a large site in several stages... One of these stages has us putting a fibre link into a remote building that has a porta-cabin next to it... As the power to the porta-cabin comes from the same building along a route we will want to run CAT5 (from the fibre switch to PC's in the porta-cabin) we have purchased some Shielded (solid-core) CAT5.

Now my question is around the shielding, as the cable will be going outside (and isn't armoured) we want to protect it in some way, it's only travelling a short distance (3-4 feet?) so I was thinking just a length of hosepipe. It would be protected from the environment and would protect the shielding from ever being 'out in the open'?

Now we enter into the grounding aspects of shielding and earth differentials!

It is my understanding that as the porta-cabin is on the same power supply as the building the earth differential is not a problem, but as we are still using shielded CAT5 do we still need to ground it in some way - as the shielding runs the risk of picking up lots of RF interference where is it being laid (right next to a big multi-phase power feed)? As none of the other equipment (patch leads, switches & PC's) will be grounded additionally (than the existing power connections) is this dangerous to leave ungrounded?
 
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Can you not get hold of some galvanised metal conduit / piping to run the cable through?

This will effectively be grounded via the cable trays that are already in place and you are following.

From my understanding (which may not be great) the cat5 cable will be grounded at each end with the RJ45 connectors and switches and any RF picked up by the trunking will be grounded from that.
 
We could, but it wouldn't totally remove the RF interference, hence the use of shielded cable...

Is it as simple as grounding the shield from the cable, which wouldn't happen without using shielded RJ45 ends (which are not standard, but available)?

My understanding is that without shielded RJ45 ends, the shield itself would not be grounded as there is no connection between it and the cores of the cable (which are grounded through the switch/pc's). In some circumstances it can actually be WORSE than using non-shielded as the fact it's there (ungrounded) it can act like an antenna (introducing RF interference)...

Can I just run a grounding wire from one end of the cable's shield to patch cabinet (which is grounded by the switch because it's connected to a power source)?
 
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Sounds feasible

Would still put it in a metal conduit though to provide better protection

Could also throw a couple of rf chokes on each end of the cat5 cable too
 
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