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Topic Title: Telecommunications question.
Topic Summary: A request for info?
Created On: 05 November 2017 07:52 PM
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 05 November 2017 07:52 PM
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MHRestorations

Posts: 40
Joined: 22 October 2017

I am not sure if this is permitted as it's not related to the regs directly, but IS related to conforming to British Standards.

I have been installing phone and data wiring since long before cat5 became 'the catch all'. But I've never been able to find a copy of BT spec CW1308 (or any of the specification). All the cable I've used till recently that was CW1308 was twisted pair TACW (tinned, annealed, copper wire) with a fairly low number of twists (around 50 per metre).

Recently purchased some cable claiming to be 1308, but it basically seems to be cat5, printed with 'cw1308'! (variable lay to the twists, striped colour codes rather than dotted, if that makes sense).

So in short, is anyone able to point me at a definitive copy of 1308?
 05 November 2017 09:03 PM
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AncientMariner

Posts: 717
Joined: 14 December 2004

I don't have a copy of a definitive CW1308 spec, but can advise of another cable which is out there in the field.

This is marked on the drum as CW1308 and also has CCS mentioned. Found to my horror that this cable is magnetic and then realised that CCS is Copper Coated Steel. Yes, a copper plated steel conductor. Besides corrosion issues, I am not sure what affect it has on ADSL or VDSL. I know that some coaxial cable is silver-plated copper over steel, but arguably for the frequencies involved for that cable's intended usage, skin effect would keep the current flow on t5he copper and silver rather than the steel. I don't think that the same could be said for CCS CW1308 and the frequencies used by ADSL and VDSL.

Clive

-------------------------
Clive S Carver GCGI IEng MIET MITP
 05 November 2017 10:16 PM
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MHRestorations

Posts: 40
Joined: 22 October 2017

Thanks Clive, indeed I've also come across the CCS stuff... i too worried about the effect of the self inductance from the steel core on ADSL frequencies. At least that has the decency not to be labelled 'cw1308'. That's what 'miffed' me. I sought out a cable claiming to be 1308, and got cat5 with a white jacket?

With reference to the co-ax with steel core, I believe you're correct that the skin effect would keep it out of the core at the frequencies of cable/terrestrial/satellite tv (even FM radio). I also have seen that used as an overhead drop in the USA, where the steel would be an advantage for strength.

Another consideration is potential lifespan. I've seen the older GPO dropwires (not sure of the number, maybe dw no.3) with copper clad steel conductors, where the conductor rusts out at a nick in the insulation (usually near the front door, so no tension on the cable) leaving an ultrathin coating of copper over rust. The source of MANY noise complaints on landlines!

let's not mention the cca mains flexes coming in from china!
 06 November 2017 12:38 PM
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Angram

Posts: 652
Joined: 23 March 2009

I think you should specify a good UK manufacturer. Or at least check with them. I have found CW 1308 to be a much abused label.

It should be tinned copper conductors with a solid colour and striped insulation: then a clear plastic wrapping before a PVC sheath.

That is my current drum but I have found them without the clear wrapping as well.

I guess CAT5 is fine for voice as well as data, so why have CW1308?

Another point is that voice only needs two wires these days, not four.
There are two wire (one pair) versions of CW1308 manufactured.

Having only two wires avoids any interference being picked up on broadband frequencies.

It can be hard to be certain what online suppliers are actually offering

Angram.
 06 November 2017 01:35 PM
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davezawadi

Posts: 3895
Joined: 26 June 2002

The old twin grey coloured dropwire was an experiment to cut costs which failed horribly. Drop wire no 10 is much better with round cross section, steel strength wires and 2 twisted pairs, and a black polythene sheath. It is very strong when tensioned, and using the correct springy twisted cable strainers makes a long lasting install.

CW1308 is being misused by some, but essentially covers multipair PVC voice cables, it is rather lossy when used for ADSL, hence the filters being included in the master socket nowadays.

CAT5 etc. is used everywhere, which makes it inexpensive, but beware of either CCS or CCA (copper coated aluminium) versions which will not last as well as copper types. It is fine for short telephone connections and of course Ethernet.

-------------------------
David
BSc CEng MIET
david@ZawadiSoundAndLighting.co.uk
 06 November 2017 06:35 PM
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gkenyon

Posts: 4954
Joined: 06 May 2002

Originally posted by: davezawadi
CAT5 etc. is used everywhere, which makes it inexpensive, but beware of either CCS or CCA (copper coated aluminium) versions which will not last as well as copper types. It is fine for short telephone connections and of course Ethernet.
But do check particular CCS / CCA cable compatibility for PoE applications ... heat calcs at present I believe are for copper-only?

-------------------------
EUR ING Graham Kenyon CEng MIET TechIOSH
G Kenyon Technology Ltd

Web-Site: www.gkenyontech.com
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