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    Noise Margin plummets in the evening

    This is a discussion on Noise Margin plummets in the evening within the Sky Broadband help forums, part of the Sky Broadband help and support category; I've seen one or two posts on this now but not seen a convincing explanation of the cause. Every evening ...

    1. #1
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      Noise Margin plummets in the evening

      I've seen one or two posts on this now but not seen a convincing explanation of the cause.

      Every evening my downstream noise margin starts to take a nose dive. Like clockwork this starts to happen around 6 - 6:30 and by 8-8:30 is at its lowest (in my case a dive of up to 7db). By 10 it starts to pick up again and by the early hours is back and stable.

      Now this is really aggravating because when the margin drops to about 6db the connection gets flaky and I have to reboot the router. As Sky Max is a rate adaptive service the router re syncs at a lower speed but of course, as the noise margin is still falling, it soon reaches 6db again so another reboot is needed. If I get past 8:30 then the connection stays stable but by morning the noise margin is back up again but the router is synced as though it was still low. This means I'm connected at about 3000kpbs less than I could be.

      So what's the theory about what's going on here?

      I've read it might be external influences such as street lighting - don't think so as I don't have any street lighting within 100m of my house. Also, the margin comes back up way before any street lighting goes off.

      I've read about internal influences such as central heating kicking in - don't think so as mine's not on and I don't have any electrical devices coming on/going off at these times.

      I've read about cross-talk between other users - maybe, but why at these times only? You could imagine that these times are peak Monday to Friday but not at weekends too.

      Any other (informed) theories?
      Last edited by Saturday; 16-09-06 at 08:39 PM.


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    3. #2
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      Re: Noise Margin plummets in the evening

      Did you ever find a solution for your problem? (or even a convincing explanation?). I think you posted your thread in September. Has there been any shift in the time period when the noise margin plummets. At the moment I am seeing the same thing, but between 8 and 9 pm.

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      Re: Noise Margin plummets in the evening

      i think it's where more people turn the internet on when they get home from work/school etc, and this could cause more noise on the network, my noise margin takes a dive as well but i just reboot when it at its lowest and then don't need to reboot for ages after, but thats just my theory.
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      Re: Noise Margin plummets in the evening

      Yes - posted in the early days of Sky BB before I'd got my head around its idiosyncrasies. Since then I've done a lot of reading and I'm still learning.

      There are a lot of factors involved but the two main ones are environmental and crosstalk.

      Environmental is a mixture of things which can cause the ADSL transmission qualities of the line to change. The biggest of these if rf particularly frequencies in the long.medium and short wave radio signal spectrum. This is all to do with the effect of the sun on the ionosphere blah blah blah. In simple terms, wires pick up a lot of rf as it starts to get dark. Other environmental factors include temperature, moisture etc.

      Crosstalk is "leakage" of signal across adjacent wires. Again it's a bit more complicated than that but essentially the more people using Sky's network (mostly we're talking at the exchange level here) the more their use interferes with others'. This isn't anything to do with bandwidth. This is about transmission of the signal and interference.

      So, in simple terms, a falling noise margin is due to electrical interference (noise) caused by the effects of the setting sun and other users.

      HTH

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      Re: Noise Margin plummets in the evening

      I have the exact same issue, going to install an xte-2005 tomorrow and see if that will help.

      Is the issue a problem with the phone cabling itself or is it something that would go away on another ISP?

      Surely the phone companies must try to do something to fix this if they want to promote adsl2+. Rewiring perhaps?

      my CRCs seems to shoot up at night but are acceptable during the day.
      Last edited by dq1; 13-04-07 at 10:05 PM.

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      Re: Noise Margin plummets in the evening

      You're sort of missing the point.

      No it's not inherently a problem with specific phone cabling though a poor quality line will suffer more than a good quality line. Fitting a filtered faceplate will often slightly reduce the size of the noise margin fluctuation. It is inherently a problem with all phone cabling.

      It won't go away with another ISP though it could be argued that Sky have exacerbated the problem by releasing router firmware which negotiates a minimum noise margin level that is inadequate for less than good quality lines. Of course, were SRA implemented then it wouldn't be a problem.

      Your CRCs will go up when your noise margin goes down. Below ~6db they'll really go up. Low in the day, high in the evening simply shows that your line is generating errors. You have a lower NM in the evening.
      Last edited by Saturday; 14-04-07 at 12:19 AM.

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      Re: Noise Margin plummets in the evening

      Quote Originally Posted by Saturday View Post
      It is inherently a problem with all phone cabling.
      And it is a crippling problem which makes the whole service flawed (at least when compared to cable broadband). With plans for virgin media to release a 20meg broadband who are customers with the choice going to choose?

      Someone on another forum pointed out these plans to me BT 21CN - Wikipedia, the free encyclopedia I would expect with the competition they will be accelerated in order to compete.

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      Re: Noise Margin plummets in the evening

      With plans for virgin media to release a 20meg broadband who are customers with the choice going to choose?
      The problem with Cable, is the coverage, I couldn't get it even if I was attracted to their offers. (although at present they have nothing to offer imho)

      I use broadband about 14 hours a day in 2 locations - about 4 miles apart and cannot get Cable at either of them.




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      Re: Noise Margin plummets in the evening

      Quote Originally Posted by NewsreadeR View Post
      The problem with Cable, is the coverage, I couldn't get it even if I was attracted to their offers. (although at present they have nothing to offer imho)

      I use broadband about 14 hours a day in 2 locations - about 4 miles apart and cannot get Cable at either of them.
      I am well aware of this, its the reason I'm now on sky. But consumers aren't going to like getting a second rate service due to their location, and it isn't exactly good business to say 'well you'll just have to move'. They are going to have to advance the network by new means. What happens when 30meg, 40, 50 meg becomes offered?

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      Re: Noise Margin plummets in the evening

      Cannot disagree, and until BT decide to upgrade their network, problem is we are stuck with such varying speeds.

      There is nothing Sky or any other ISP can do about this, unless they develop a new technology that copes well on old copper wires.

      Even VM are resorting to reselling BT's ADSLMAX to compete with Sky and the others, however VM won't be offering 20mb or 50mb to those customers, as they still are in the hands of BT.

      The amount of money BT make, they could easily rewire the streets etc, will they do it? Nope!




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