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Author Topic: ******* Aluminium  (Read 6760 times)

waltergmw

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******* Aluminium
« on: September 18, 2009, 07:05:08 AM »

Hello Everybody,

I'm trying to guage whether Aluminium cabling is a very significant problem or whether most consider it just a nuisance and bad luck.

I expect that it is used quite extensively, especially on the E side, as we see quite a few mentions of it in widely differing parts of the UK.
I have noted Milton Keynes, Belfast, Exeter and Winterbourne Stoke as recent examples.

I would be very grateful if all who know they are affected could post their Exchange Name, County and E for exchange side or D for distribution side of their PSP (Green Cabinet) here. I'd be pleased to have a few PM's from any directly involved !

Thank you all very much in advance.

Kind regards,
Walter
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Tweedman

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Re: ******* Aluminium
« Reply #1 on: September 18, 2009, 07:24:27 PM »

Hi,My first post so be gentle.Aluminium does not greatly increase db on a line as some people would think.The main problem with alu is that it is more susceptible to corrosion than say copper and more so if its a poor grade of alu.The main cause of poor adsl and high db on a line is that a lot of e side cables are 0.4mm conductors and this is just to small.The difference between say a 0.5mm copper and 0.5 aluminium cable would only be a couple of db.
« Last Edit: September 18, 2009, 08:02:40 PM by Tweedman »
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general disquiet

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Re: ******* Aluminium
« Reply #2 on: September 18, 2009, 09:03:26 PM »

If you have two cables of equal length and equal thickness, one copper and one aluminium, there will be greater attenuation on the aluminium cable than on the copper - unless the laws of physics have suddenly changed.  You can compensate for this by increasing the thickness of the aluminium cable.   Add oxidised cable in damaged ducts or cable simply laid into the ground, oxidised joints and aluminium is a nightmare.  Aluminium joints on copper runs also cause problems.  Stir into the mix changes of cable thickness and it all gets really nasty - but the bottom line is that aluminium does not have the same electrical properties as copper and thicker aluminium doesn't always seem to have been used.

Some facts and figures to demonstrate this, based on a real cable around 3-3.5 km in length - figures gleaned from BT:

Aluminium 100/0.5   Attenuation = 57dB @ 300KHz  - existing cable
Copper     100/0.5   Attenuation = 36dB @ 300KHz  - estimates for possible replacement
Copper     100/0.6   Attenuation = 29dB @ 300KHz   - ditto
Copper     100/0.9   Attenuation = 22dB @ 300KHz   - ditto

The difference between copper and aluminium of the same diameter is around 21dB - and not "about 2db".    If you follow the logic of this, an aluminium cable has roughly the line attenuation of a copper cable of twice the length.  Put the other way the attenuation of an aluminium cable suggests it is twice as long as it actually is!

Let's get the data for walter and see what the reality is around the country!
« Last Edit: September 19, 2009, 09:27:26 AM by general disquiet »
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waltergmw

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Re: ******* Aluminium
« Reply #3 on: September 19, 2009, 12:01:36 PM »

Come on you splendid and erudite people - there MUST be many who have heard whispers about aluminum in the area from BT.

Thanks also to the General - when you remember the dB is a logarithmic scale it does show what a vast difference there is in the signal.

I also believe Tweedman is correct in saying some of this brittle rotting aluminium was only 0.4 mm in the first place. It's a pity BT were too shy to provide figures for that.

Kind regards,
Walter
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Tweedman

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Re: ******* Aluminium
« Reply #4 on: September 19, 2009, 12:25:12 PM »

Come on you splendid and erudite people - there MUST be many who have heard whispers about aluminum in the area from BT.

Thanks also to the General - when you remember the dB is a logarithmic scale it does show what a vast difference there is in the signal.

I also believe Tweedman is correct in saying some of this brittle rotting aluminium was only 0.4 mm in the first place. It's a pity BT were too shy to provide figures for that.

Kind regards,
Walter

Hi Walter,The problem is that most cabinets have 0.4 e side conductors which i would say is mainly copper but some aluminium still exsists.I will give you an example of how poor even copper is when its only 0.4.My own line is approx 2.7 km in lenght,1.3km to the cabinet on 0.4 copper with a db of approx 30.The d side is 1.4km on 0.6 copper and has a db of approx 13 giving me a total of 43db,shows what a big difference the conductor size makes.These figures are spot on correct as i have measured them personally.

Hers a copy of my line stats.

Line Mode G.DMT   Line State Show Time 
 Latency Type Interleave   Line Up Time 02:19:38:04 
 Line Coding Trellis On   Line Up Count 1 
   
 Statistics Downstream Upstream 
 Line Rate 7808 Kbps 448 Kbps 
 Noise Margin 11.6 dB 22.0 dB 
 Line Attenuation 43.0 dB 22.0 dB 
 Output Power 19.8 dBm 12.3 dBm 
 K (number of bytes in DMT frame) 245 15 
 R (number of check bytes in RS code word) 20 16 
 S (RS code word size in DMT frame) 1 8 
 D (interleaver depth) 64 4 
 Super Frames 14322485  14322483   
 Super Frame Errors 392  70   
 RS Words 1947858024  121741105   
 RS Correctable Errors 15045289  10764   
 RS Uncorrectable Errors 7633  0   
 HEC Errors 322  0   
 OCD Errors 1  0   
 LCD Errors 0  0   
 ES Errors 0  0   
 
« Last Edit: September 19, 2009, 12:30:00 PM by Tweedman »
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waltergmw

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Re: ******* Aluminium
« Reply #5 on: September 19, 2009, 12:38:55 PM »

Thanks very much Tweedman. If anything this demonstrates that we need FTTC even more desperately than many may think.

Kind regards,
Walter
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general disquiet

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Re: ******* Aluminium
« Reply #6 on: October 01, 2009, 08:44:06 PM »

There just have to be more of you with aluminium cables - or else why are BT making such a big deal over mine and Walter's?
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waltergmw

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Re: ******* Aluminium
« Reply #7 on: October 02, 2009, 12:08:38 AM »

I  believe I've read of aluminium in Exeter, Milton Keynes and we've heard about Belfast.
I agree with the General that it almost certainly has to be quite widespread. However how many know to ask the question in response to the "your line's too long" excuse, is another matter. Come on all you budding Sherlocks !

Kind regards,
Walter
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Ezzer

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Re: ******* Aluminium
« Reply #8 on: October 04, 2009, 02:26:53 PM »

in east anglia there is some ali dotted about.the majority of the network is 0.5 copper. I don't come across 0.4 much. 0.63 copper and 0.5ali are the next most common.we can look up the network records on our laptops and see what lies along a route. occasionaly one route can have a mixture of cable types. this complicates things when using a megger to locate some faults.Used to use a pair of circular slide rules for distance/resistance. But know our hawks have a feature where we can enter a list  of distance and cable type along a route to give a final distance if it's differing cable types along a route

One of the things I check for on broadband faults is the network records.most cab's have more than1 e-side cable so I can have an option to change the line to another cable with less loss. the losses to cabs are recorded via something called seam. although this can go out of date, one cab I can think of had part of the e-side upgraded so I look at which cable the dsl is on to that cab and change it straight away.

A real trouble spot with a very long line had problems where a coastal village had line losses in the high 60's. I've been to loads of properties there replacing rf2's with rf3's correcting star wiring fitting dsl front plates and everyone is on a fixed 0.5mb service. This summer with the removal of something called a Gfeller 4.5km of new 100pr 0.9 copper was fitted. 1st time I was happy to get a dsl fault there this august and the new cable was ready, 2.5mb; ("yes!"). God knows how much that cost  ???

Generaly everyone hates working on ali because it's so brittle. Have to be carefull when delving in a joint because it's all to easy to add several new faults when trying to fix the one your working on. The new mechanical joint closures help
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orainsear

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Re: ******* Aluminium
« Reply #9 on: October 04, 2009, 02:37:39 PM »

most cab's have more than1 e-side cable so I can have an option to change the line to another cable with less loss.

I was going to start a topic about this but I'll ask it here instead - when a new cable is wired in what is supposed to happen to the old one?  Is it marked up as faulty and not used again?
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Ezzer

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Re: ******* Aluminium
« Reply #10 on: October 04, 2009, 11:30:38 PM »

if the oldone is useable and not faulty then it stays in situ
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waltergmw

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Re: ******* Aluminium
« Reply #11 on: October 05, 2009, 12:00:35 AM »

@ Ezzer,

Thanks very much for your comments. I can well imagine that an aluminium joint must be an absolute nightmare, but I assume if most of it is on E side cables they don't get disturbed so much. Is there any way of identifying aluminium cables externally, or weren't they marked in the 60s ?

It's very good to hear that some cables are being replaced with thicker copper. A year ago I got a retail quotation for 500 m of 100 pr 0.5 mm catenary at about 3,000, but when I asked about 0.9 there was much sucking in of breath and I think it was about 4 times more expensive due to the lower volumes sold - as well as the extra copper.

Re removing cables, I suppose if there are several in a duct, that's a good reason to leave it alone even if it is faulty. I've seen several around her left with manky ends in the bottom of joint pits and some left dangling in the wet on poles.

Kind regards,
Walter
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general disquiet

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Re: ******* Aluminium
« Reply #12 on: October 06, 2009, 07:51:52 PM »

@Ezzer

OK, can you explain - please!  What on earth is a Gfeller?

Which village got their line upgraded?
« Last Edit: October 06, 2009, 08:30:47 PM by general disquiet »
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Oranged

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Re: ******* Aluminium
« Reply #13 on: October 08, 2009, 11:54:37 AM »

Walter, there's an interesting post re. aluminium today on Thinkbroadband  :lol: :

Quote
I found out what they were doing, shocking.

They laying ali. Ran out of copper pairs as too many faulty pairs, copper too expensive so ali been laid to ease capacity. Was advised by an engineer present to not get a pair swap because of this. A new cabinet is been placed as well which is to shorten the loop length but he advised me the longer copper will still perform better.

http://forums.thinkbroadband.com/o2/3712538-wonder-if-o2-are-joining-in-ftthfttp-trial-i-want-100mbps.html?view=collapsed&fpart=all&vc=1
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waltergmw

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Re: ******* Aluminium
« Reply #14 on: October 08, 2009, 12:54:05 PM »

Thanks very much oranged. I am quite astonished that BT were prepared even to countenance aluminium.
Perhaps the only excuse might be if this is a temporary fix until the fibre is laid ?

Kind regards,
Walter
« Last Edit: October 08, 2009, 01:02:17 PM by waltergmw »
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