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[graevine1]

You state I fail to supply any references or link, as you claim to be an oracle on the subject you clearly should be fully apraised of all facts without any assistance before profering advice to others. We believe all can determine the facts by reading this thread. The fact remains that customers who have a line attenuation greater than 10db per kilometer have a line requiring maintenance or an "uplift". QED

[kitz]

I really do believe this has got very much out of hand.

This all started as a result of this thread here
http://forum.kitz.co.uk/index.php/topic,1331.msg46375.html#msg46375

Because I dared to state a reality "The 10dB figure is a "pluck out of the air" figure and bases no reality on the true situation of the vast majority of lines in the UK".

Because I stand by that fact, you seem to be taking every opportunity you can to rant and discredit me.  Spreading rumours and implying that because I stand by that I and others are in the pocket of BTw.  I have heard this fact from several sources and this is downright libellous.

You have a serious issue with BT, I don't know the exact cause of it, but to contact people and spread malicious rumours is something I do take big issue with.

Believe it or not I do actually believe that BT can and should do more for some lines, but Im a realist and know the huge cost of investment.  I still stand by the fact that the vast majority of lines in the UK are more than 10dB. That would appear to be a fact and until you come up with evidence to the contrary, I will let others make up their own mind.

In your vendetta you have obviously called Phil into this.. but I bet you havent told Phil the whole story have you.  You had already been advised earlier this month that it would be better to bring your rants about BT into a separate thread in the tech chat section.  Continuing to rant about BT and the 10dB situation in totally irrelevant thread in which are discussing other issues and taking the subject off topic does nothing to help the original poster as to why they come here in the first place.

I have been fair and given you free rein to rant at BT, the only times I took exception is when it was totally irrelevant to the topic involved and that is why I brought it into this thread.
The fact that I have had several enquiries from users of this forum as to why you are PMing people giving them your phone number and asking them to call you actually has disturbed several people who come to these forums asking for help.
I will not stand by if users who come to this forum are concerned and find it a little strange.. but the audacity to also imply that I and other members of this site are in BTs pockets is libellous. 

You think Im pro-BT... then why would I actually suggest to someone specific that they contact you and see if there is anything that can be done about your "cause", because I cant go down to London.  If that person has contacted you or not I don't know..  I just made the suggestion that maybe someone should to see if it could help further your cause.

The basics of this forum are that we will try to help anyone - who ever their ISP is, but ranting at BT rather than try to investigate some of the basics has taken several threads off topic.. and that is what you have been politely requested not to do.  If you dont agree to the rules then I suggest you find elsewhere to take your rants.

>> Now with reference to the brightly coloured graph in this thread it I believe has little practical relevance to the practical situation in the Uk but is an interesting guide to the overall picture and is of course drawn up by whatever means by a group in Australia.

Please read it again.. I didn't hide the fact that it was done for an Australian company.. but  adsl technology is the same world-wide and runs on the same frequencies.  I also stated that when I had coded the checker that I ran it against every UK line stat I could lay my hands on to see if it also came within acceptable parameters - which it did.  There may be some differences in the amount of copper used.. just like many different areas of the UK uses different amounts of copper in the line too.   

Offensive and incorrect posts such as some of yours do nothing to give you credence.
No-one on this site has ever pretended to be a competent engineer, if I dont know I will say so, and I wont blindly make facts up for the sake of it. 
This site aims to give information to help people diagnose problems and I am not about to let it be destroyed by someone with a huge chip on his shoulder about BT, and then attempts to spread malicious and untrue rumours simply because I dared to state that from my observations the average line length is more like 14dB.

I am entitled to have my own opinions of the running of BT...  and just because it may differ from yours doesn't mean that I am wrong... nor does it mean that I am in BTs pockets (incidentally an insult you would appear to dish out to anyone who disagrees with you).. nor does it give you the right to make up things as you go along.



>> it is not for anyone here or anywhere else to condone a substandard network or suggest to customers that they put up with 15db or 20db,

Please stop twisting facts - what we have done is said that 14-15db for km it appears to be the average and far more realistic than your figure of 10db per mile or km.

I have still yet to see some official evidence to support your claims that adsl attenuation should run at 10dB per mile or km.  I'm aware there are regulations for voice... but afaik nothing for adsl.

[kitz]

/snip /
 - is this at 300 kHz or at a weighted average of the frequencies in use or.....

If longer lines have fatter copper to compensate (on voice) then the dB/km will be lower in any case, I've seen numbers like 62 dB over 10 km on a thick overhead line.

This is something that did actually strike me a couple of days ago..  I still dont know where grapevine has got the figure from that lines should be no more than 10dB per mile... but something that did occur to me is that as we all know voice is transmitted at a lower frequency.. and as such attenuation for the voice frequencies would be much lower than they would be for adsl.
I believe that BT do have regulations as for the provision of voice, but afaik there inst anything regarding the specifics of adsl.

Therefore if this document of "proof" exists somewhere and does relate to voice frequencies, then surely we cant use figures obtained from an adsl modem/router as a comparison measure.

It is a possibility that many,many years ago when laying lines for voice only that they did perhaps use higher gauge copper wire to compensate very long lines and to bring things up to a standard for voice.

I also have grave concerns about people using adsl routers to measure attenuation.. different routers report different figures and its something Ive been stating elsewhere for several years. 

Fore eg

A sample of stats on my own line using different routers.

As the crow flies 160m
Actual cable length 600m

7dB - BT voyager 2100
8dB - Speedtouch 576
9dB - SAR110 (VIK-2.1.040311a)
12dB - Netgear DG834G
21dB - Solwise SAR110 (original firmware)

[setecio]

How could there be regulations for adsl? The wires were designed for voice and adsl over them is a by-product. You can't put regulations on wires that relate to a system that they were never designed for. That just means replacing the old system with a completely new system designed for adsl (ie thicker wires) to meet the new regulations.

[Astral]

That just means replacing the old system with a completely new system designed for adsl (ie thicker wires) to meet the new regulations.

I seem to remember when BT was privatised that the biggest asset they owned, by far,  was the copper cable network. Anyone with an ounce of commonsense would realise that it is not a practical proposition to replace that network over a short timescale.

My feeling is that another transmission technology will be developed long before the copper wire network gets replaced.

[Ezzer]

Stetecio has got it spot on. the cost of providing new cableing for several customers be it for 10,20,50+ plus lines is very expensive, lately much more so with the incredible increase in costs of raw materials. The BT group has to work with a net work originaly designed for voice not data. Doubleing up on pairs in therory can improve a signal, this cannot be done in the network for a number of good reasons. A cable directly feeding one property (the wire from a pole/distribution point to the property) this may be done, but has as much chance or creating problems for broadband (and other issues too long to go into)

The last time I looked from memory the OfCom licence requirement was the ability to provide a data connction to at least 14.5kbps. 64kbps with a mid band connection if avalable on a relavent contract with your telecom provider. Now with the advent of broadband 0.5mb is the minimum reasonable speed, that is assuming that the total cableing is capable of supporting this (which sometimes on the odd occasion isn't possible within reason). I've never heard of any target db loss per set distance so stating any more than 10db/km is substandard at 300khz is a fiction in my opinion.

From my experience any bt broadband engineer would do their best to get the optimum service to any customer. Long line issues you do your best to look at the optimium cableing, sockets etc to get a fair and reliable service.

I thought this string started as a forum to gauge a rough ball park guide. I've never worked to an expected figure per kilometer because of the variables I come across. Just I know typicaly beyond 7-7.5km the line lenght "may" become a real issue. this string is becoming a bit ugly me thinks

[Astral]

A thought has just occurred to me; with the current astronomical price of scrap copper would it not make economic sense to to replace it with  fibre optic over a large part of the network?

[Ezzer]

Something called 21st century network (or 21CN)

It's happening now & the budget is massive. although there's a lot of network to get through so it will take time

[Astral]

>Something called 21st century network (or 21CN)<

There you are, graevine1; BT is addressing the problem, so we won't need to hear anything more from you on this subject.

[roseway]

Doubling-up wires is just as likely to degrade the ADSL signal as to improve it, because the two pairs will have slightly different transmission delays. In the worst case this difference would be such that the two signals would arrive at the end in opposite phase and cancel each other out.

[soms]

Doubling-up wires is just as likely to degrade the ADSL signal as to improve it, because the two pairs will have slightly different transmission delays. In the worst case this difference would be such that the two signals would arrive at the end in opposite phase and cancel each other out.

Thanks roseway and Ezzer for clarifying that. It was just something I have heard done and wondered if it actually did make any improvement.

With regards to 21CN, the first stage is only a converged core network to replace existing seperate platforms.

Unfortunately 21CN in its first phase will not be FTTC or FTTP, although I agree, with the costs of copper and the theft of copper becoming such a cost, fibre suddenly looks like an attractive option.

Apparently Openreach are carrying out consultations and have conducted trials and all that so we will see what happens.

I think a simple way to look at things at present is that 21CN is BT wholesale's realm, with most of the work being done by BT Operate, which makes it a separate infrastructure to the access network, which is down to Openreach to develop as they see fit.

[PhilT]

The fact remains that customers who have a line attenuation greater than 10db per kilometer have a line requiring maintenance or an "uplift".

Another BT official "price point" was the original 3.5 km limit for 2M at 41 dB = 11.7 dB/km.

There is a mechanism built into MaxDSL to counter deterioration in the local loop - during the 10 day "training" period about the only thing that happens different to any other time is that the lowest sync rate achieved is clocked as the "Maximum Stable Rate" or MSR.

If the sync speed subsequently deteriorates below 70% of the MSR (the 70% being the Fault Threshold Rate or FTR) then the ISP can raise a fault due to reduced service speed.

So there is a mechanism in place to counter any tendency to long term neglect of the loop. This wouldn't address any "Day 1" high attenuation issues though.

FWIW the 21CN project doesn't address the local loop or its quality, it starts at the exchange and simplifies systems upstream of there.

Phil

[PhilT]

Some info :-

1. Enhanced spec Openreach tie cable for LLU to approach Cat 5 performance - "Attenuation : 14 dB/km @ 300 kHz, 31 dB/km @ 1 MHz, 103 dB/km @ 10 MHz" from here.

2. CW1308 doesn't define the attenuation spec, but a cable supplier quotes typical values of 45 dB/km at 1MHz which is 45% more loss than the above spec.

If the 45% factor also applies at 300 kHz (bit of a guess, admittedly) then CW1308 would be 10 dB/km. Back to the "5.5 km = 55 dB" BT figure.
[Admin edit:  "If" the 45% factor applied at 300 kHz it would be 21 dB/km*]

If, as I suspect, routers report a weighted average attenuation across the frequency band then the fact that attenuation doubles over the ADSL downstream frequency range is important. A higher speed line using all the frequencies will show higher attenuation per km than a long low speed line struggling with only low frequencies. The bits/bin allocation of routers can also vary, some filling up from the bottom of the frequency spectrum and others spreading across the whole available spectrum.

Phil

[Admin Note]
It has come to our attention persons have been pointing to this post as supposed proof that attenuation on CW1308 cable should be 10dB/km. Hence the need for the edit.
Since CW1308 has more loss than Enhanced spec, this additional loss should be added on to the original figure, not subtracted.
The rest of the post is not disagreed with and is something already stated/discussed elsewhere.

[graevine1]

Thank you Phil, the weakest link in the cable feed is the customers end ie the CW1308 which would be approx 10 dB/km. That cable being the lowest cross-section of copper.

I received confirmation of the 10db per kilometer from the Chairmans office just over a year ago. So I and all others should hold them to that.!!!!! Anyone who says any figure greater is not in need of maintenance or "uplift" is simply missleading the service receiving customer

If any contract has caused a lower grade cable -v- distance to be inserted into a length then the words are  -tough- it just requires an "uplift" ie replacing so as to return an acceptable service to the customers. The problem that is occuring is short lengths being 'let in' to repair faulty runs in cable lengths, hence adding extra joints etc with their attendant losses. Another is "E" side cables (those from the exchange to the CAB) having had water ingress from a faulty joint or for whatever reason not being able to be ever returned to original specification by the passing of the compressed drying air into the length from the exchange.

I get extremly annoyed when individuals profer their opinions (without any formal training or qualifications)  and appear to say accept 15 or even 20db per kilometer line attenuation, with its intendant lower SNR/ crosstalk,'cutting into busy' liability. It does however require certified, calibrated test equipment to establish the figures as routers only give a guide figure.

Its true openreach inherited a "national asset" and as such must maintain it to an acceptable standard

Astral states "I seem to remember when BT was privatised that the biggest asset they owned, by far,  was the copper cable network." Is anyone now suggesting we should accept a degrading local network.?

Astral then states "Anyone with an ounce of commonsense would realise that it is not a practical proposition to replace that network over a short timescale." But we the customers should ensure that no one allows the twisted copper pair network to deteriorate, and that in many instances is the situation today.

We may see FTTC fiber to the cab, but I doubt we will see for many years, other than to 'new build' and then not all, FTTH fiber to the home, IF EVER !!!!! to other than a very few!

[roseway]

I get extremly annoyed when individuals profer their opinions (without any formal training or qualifications)

And I get extremely annoyed when you make such unsupported assumptions about people who disagree with you.

This thread has become no more than a slanging match and is going round in circles now. I'm locking it.