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Noise Margin

Cign
Grafter
Posts: 42
Registered: 17-08-2007

Noise Margin

I have noted various posts regarding difficulties with MaxDSL upgrades quote Noise Margin figures ie. "noise margin 8dB". I have been watching mine over the last few days and note that it fluctuates wildly, as per the graph below:



I thought (probably wrongly) that the noise margin was set by BT. Is the fluctuation something I should be worried about for MAxDSL upgrade. I assume this is being carried out at the moment although I havn't been told about it!

And why is it that my Sync speed stays constant until I start doing something?

Any advice / help much appreciated.

John
12 REPLIES
N/A

Noise Margin

That does seem to be fluctuating wildly. I have never come across one like that before. There are many tips and tricks to stabalise a weary line such as removing the ring wire.

http://www.kitz.co.uk/adsl/lowSNR.htm

Sometimes using a better modem can also help. Obviously if your on a USB device a router would be better (usually). Other than that there is not much you can do unless you can somehow prove it is a fault on your line and have BT come and look at it.
Cign
Grafter
Posts: 42
Registered: 17-08-2007

Noise Margin

phearfactor, thanks.

These figures are for a Netgear DG834GT router. I was on PAYG 1GB and have had no problems for ages. According to the router stats I am synced at about 3GB at the moment although definitely not getting that speed. The Noise Margin figures are at 10s intervals but it varies by the second according to the router stats.

Line attenuation remains steady at 43dB (about 3miles from exchange)
Why doesn't the upstream Noise Margin (21dB) change, after all its using the same wire?

Thanks again...

John
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Noise Margin

Not sure why the upstream never changes. It never changed for me either but the downstream did. I had over a months worth of waiting (its only just changing now) where my sync speed and actual speeds were completely different.

The router is a good one and will give probably the best line stats as any modem on the market.

It sounds like you have only recently been upgraded and BT are still testing the line. As such they can adjust the SNR up and down, if it flucuates like it is doing you might find yourself on interleaving - which will make the line more stable.

They say it takes about 2 weeks from start to finish but it has taken about 5 weeks for me and its still not right. I would suggest looking into the ring wire but other than that it lies flat on BTs head to sort it out. Once they get your line figures back they will change settings etc to make things more stable.

I wouldnt worry too much about it, because your so far from the exchange I guess its unstandable that its struggling to perform at 3MB sync speeds. I think its more likely you will get 2MB with interleaving switched to on. If you dont know what I mean by interleaving try having a search on the forums, its not the easiest thing to explain but it generally just makes unstable lines more stable but effects your latency. So if your a gamer or us latency based software its not a good thing but it does add a lot of stability on the longer lines such as yours.

Good luck Wink
Cign
Grafter
Posts: 42
Registered: 17-08-2007

Noise Margin

I looked at the ring wire article you suggested. I have an ADSL equiped master socket so it probably wont make too much difference. I might though invest in some Cat 5E cabling for the ADSL extension to upstairs rather than rely on the old BT phone cable as at present.

It would be nice though if you got notification of when BT start playing with the line rather than just having to make assumptions!

John
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Noise Margin

ive attempted this ring wire modification (blanked pin 4 too as a precaution, seen as it doesnt do anything) so hopefully thatll cut down internal noise.

unfortunately my cable outside is 2 rather chunky copper cables so i dont think there is much way i can improve that :/ i was hoping i would have twisted pairs comming into the house...

but ill see how my connection goes, connected at 6.3mbps now, which is usually quite unstable, shall see what happens.

Update as i write: the router sucks, going back to the modem, had some solid connections from that
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Noise Margin

Yeah cign I also have an ADSL dedicated faceplate from BT and they work much better than disconnecting the ring wire anyway so dont worry about that.

It may be worth changing the cabling although the best way to check this is simply hooking up your router to the face socket with a short cable. Use wireless and see what sort of speeds etc it is getting, obviously if its alot better maybe a better quality cable will help. Best to try that before you plump for some expensive cabling because there is a good chance it will do nothing.

graz the two copper cables are very old I believe and this will most likely be whats causing the problems. There is only one way I know of for getting BT to replace it, a fault being reported on the line regarding the telephone side of things. Also a router is usually better than a USB modem depending on the quality of it, the more you spend (usually) the better it is.

I would recommend the GT as cign has (see above).
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Noise Margin

Hi cign1,

May I ask.. how did you manage to render a graph like the one you have posted using the stats from you DG834GT?

In reality, the SNR on your upstream does vary - but your modem doesn't see it - it's only the remote end (the DSLAM) that can see the fluctuation in SNR on the upstream (or the downstream channel to the remote end).
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Noise Margin

thanks for the recommendation, but ive already ordered a linksys adsl router modem Smiley

and youre right, it is most possibly the cause, which sucks, but would BT replace the line on request?
Cign
Grafter
Posts: 42
Registered: 17-08-2007

Noise Margin

gotdsl

I used a program called RouterStats that I found whilst browsing:-

http://homepages.nildram.co.uk/~vwlowen/internet/files.htm

This interogates the router and reads off the stats and plots them for you.

You can set the time period and tweak the graphs to your liking, it also keeps a simple log of the figures which you could export to Excel or similar.
I had a little difficulty getting the right html page from the router but the programs built in help pages are quite good.

Cheers
John
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Noise Margin

cheers cign - most useful Smiley
GersFans
Grafter
Posts: 191
Registered: 30-07-2007

Noise Margin

Quote

http://homepages.nildram.co.uk/~vwlowen/internet/files.htm


An excellent little program, great find!!! Cheesy
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Noise Margin

top find that, it will show PN some problems I am having!