Cat5 / 5e / UTF / FTP ..?

[T i m]

Hi All,

I was trying to advise my brother-in-law who is doing an office refir / layout change / building job yesterday and the customer wants some extra network points in the new office while they are there.

This means running new 'cables' from the comms / patch rack, above a corridor, up through some trunking and around the wall trunking to the points (voice and data). The runs will be around 75m.

There seems to be a mixture of cable descriptions round the building from what I would describe as 'straight Cat5' (these seem to be used for shorter runs) to thicker 'Cat5's with additional markings of FTP / UTF (if I've read it right).

Am I right that these are 'foil' screened UTP (so wouldn't that make it STP..?) and am I also right thinking that to make the foil 'work' it would have to be earthed at the patch (or at least only one) end?

Also, if you use the screened type cable to the patch (and the patch panel has the metal surround round the RJ45 sockets) would you also need STP patch cords to continue this concept to the HUB / Switch?

From memory I suggested that Belden cable was good stuff (used some foil screened RG58 at Heathrow terminal 4 when I was Comms Engineer a few years ago) but their electrical supplier suggested it was 'expensive' and no different to cheaper brands (but specified by local councils ..?).

Is it still 'good' or is it all much of a muchness (It's been a long time since I've bveen involved in such stuff) ;-(

All the best ..

T i m

p.s. I hope to use some leftovers for running down to my workshop so that will be the diy link ;-)

[Lurch]

On Thu, 27 May 2004 09:08:47 +0100, T i m strung together this:

Helllo.

Yep, that's pretty much it. Foil Twisted Pair is similar to STP.

Not usually, the STP is generally installed to reduce induced noise in the run. The patch panel itself is usally fairly well shielded. That's not to say you can't fit STP patch cables, it's just not usually neccesary. Unless the run is very noisy, e.g. running by heavy mains cables or through\by large inductive devices, then it is very unlikely that STP\FTP is actually needed. I've seen some people use it just so that they don't have to pay any attention to the proximity of mains cables!

[stefek.zaba]

Yes; and yes - if the existing FTP has been put in for function (as opposed to merely conforming to a spec without the cable installer being bothered about doing the job properly ;-) the patch panel will have a Suitable Means of making off the foil connection close to the normal 8 IDC connectors for the 4 pairs, along with a gert big earthing tag somewhere which will have been appropriately connected to the local metalwork.

No, as the place where the excessive interference is happening is not (we hope!) in/near the comms cupboard where the patch panel is, but somewhere along the 75m run you mention.

Belden-schmelden - it's good stuff, but so are most other "proper branded" cables (Brand-Rex, Molex, ...). I'd prefer not to skimp by getting "I Can't Believe It's A Networking Cable" own-brand gubbins, but it's your (b-i-l's) choice...

No problem, though if each run is actually 75m then you're in pessimal shape for leftovers - yer standard reel is 305m (that's metrick for 1000ft) so your b-i-l will get 4 runs out of each reel leaving you with a paltry offcut of 5m. Now, if he needs 80m for each run, you'll have 65m leftover in each reel. (By "reel" I mean "box", but it's conventional to call it a "reel"). For home use, it's quote OK to leave the shield unconnected.

Hope your b-i-l knows to be gentle in installing it, *not* to let it kink, definitely *not* to pull any kinks tight, or tie knots in it "for strain relief" - the signals it's carrying are a trifle more delicate than 20A of 50Hz ac lumbering through at 240V!

[Peter Parry]

STP, unless considerable care is taken over the overall earthing and bonding of the system, often causes far more interference problems than using UTP.

[Dave Gibson]

Agreed, and also has a lower cut-off frequency (350MHz for Cat 5e UTP) due to increased capacitance to ground (not a problem for 10/100Mbps systems but can be problematic for extended run Gigabit upgrades IME )

Dave

[T i m]

Firstly thanks to all who have replied so far.

Further investigation of the building seems the first (75%) instalation of UTP was done with Cat5 FTP and subsequent additions have been done with straight UTP Cat5.

One end of the building is probably 10m from the boundary of a electric generation station, with all the humming and buzzig clearly heard though an open window?

So foil or not to foil now..?

All the best and thanks again ..

T i m

[T i m]

K ..

Ok .. I was thinking more along the lines of is the shield grounded at the patch or is the shield simply taken to the hub / switch IF an STP path is used and grounded there?

Unless the run is very noisy, e.g. running by heavy mains

Well in this instalation there are loads of cables of all types running around each other and I don't suppose my BIL has been sanctioned to do any separation of the existing stuff?

Where it's in wall trunking it is generally is different sections of the trunking though ..

All the best ..

T i m

[T i m]

On these Krone patch panels there is a little tin box that cobers the back of the punchdown that I assume picks up on the sheild?

Ok, makes sense then.

LOL ;-) Fair enough. But I don't suppose anyone has been fired for buying Belden, Cisco etc ?

Calcs noted ... I was hoping there might be a coplete run spare .. .

Well, he does because I told him .. getting through to his spaks is another matter ... I asked him aboyt earthing my workshop on 20M of SWA from the house and the idea of using an earth rod and isolated earth at the workshop end .. his answer 'as long as you have an RCD you will be alright ..?

All the best ..

T i m

[T i m]

Noted .. Ta.

T i m

[T i m]

Hmm, so, So Cat5e that's good for Gigabit, "isn't" when its FTP Cat5e?

Ok .. I think in this case the sheilding (assuming it works) might be more important than the *possible* gigabit upgrade later?

All the best ..

T i m

[RichardS]

You could be right. UTP suffering interference isn't going to be any good for gigabit either!

If it's an isolated bunch of points that are close to the substation then perhaps a single fibre run to that and a localised switch would be a better solution if they ever do need to u/g to Gigabit.

-- Richard Sampson

email me at richard at olifant d-ot co do-t uk

[Peter Parry]

If the installation is being done by an electrician I'd go for UTP. The chances of the average electrician knowing how to earth and test the RF earthing of STP such that it does its job of minimising interference are zero. In high noise environments the screening, if incorrectly done, simply propagates the noise everywhere within the network cabling.

[T i m]

;-)

Swat I thought and / or making use of the existing cable and run a local switch near the points (still only a 100M cable into each server?)

Wouldn't help the voice points though .. ;-(

All the best ..

T i m

[Ian Stirling]

I wouldn't have expected high amounts of interference from a power station. Can an AM radio be heard without interference?

[T i m]

Hi Ian,

Sorry for not replying .. not been back here for a while ..

Good point re the radio interference and no I haven't checked (although I had thought about it).

I was looking at the patch panels today and nothed they were (mostly) FTP ones with the FTP cable shrouded in the litte tin covers.

I also noticed that there were earthing points on the backs of each of the existing patch panels but no (external) earthing? The same applied to the cabinet itself.

The empty BT cabinet next to it had earth straps on the sides, front and back and each of the modules (there were no modules in there but the earth tags were still there?).

All the best ..

T i m