BB woes continue

So my BB woes continue. Over the last 3-4 weeks my BB has been glitchy, I've been on a fast path 24M 6BdB profile, it never disconnects but it would just stop. So I contacted CS and they dropped me onto an interleaved 8M 15dB profile.

Not only does my connection speed drop from 7Mb down to 5Mb, the reliability gets even worse, the lines drops and resyncs half hourly but then it sometimes drops and resyncs every minute. I also noticed that after the change my upstream attenuation and snr margin also now drop to 0dB periodically.

So I ring up CS again and they put me onto an 18dB profile, now this does stabilise the line but instead of dropping every half an hour it now stays up for 7-10 hours.

The line shows no faults and CS seem to think that it's quite acceptable to keep on increasing the SNR margin which I'm obviously not happy, even more infuriating is that I've been running at 7Mb for quite a few years until the problems with the line started some 2 years ago.

Back in July last year, I had a new router (replaced my Netgear DG834N with a DGN1000), new face plate (replaced my ADSL Nation with a BT faceplate), new external junction box and a line fault fixed which I'd been trying to get fixed for the previous year fixed.

Anybody got any ideas or words of wisdom especially as why increasing the SNR margin made the line less stable and why now on the higher margin both the upstream attenuation and SNR margin periodically show as being 0 in the router stats , the provider is Talktalk and I have to admit their general BB service has been pretty dire. Never used to have any problems like this with BT.

Try monitoring the line with RouterStats. http://www.vwlowen.co.uk/internet/files.htm

Here's a quick trace I've just done

http://img.photobucket.com/albums/v280/IAmATeaf/snr-...

Noise has got worse? Tested from the test socket? Tried with the old dg834N?

Why the old router, the 834 may perform better, i.e. problem has been there ages, but the 834 handled it better?

My previous problem was that not only was a lot of noise on the line, the 834 when synced would also add to the noise on the line. Had an engineer out who fixed the noise on the line, replacing the 834 with a DGN1000 resolved the noise that the router was introducing.

What I don't understand is why does increasing the noise margin actually make the problem worse?

Looking on the graph the suggestion is that this is not just random noise, as the noise spikes are consistently high, but something that is producing noise perhaps at random times, but of a high amplitude.

A router introducing noise that affects ADSL is rare, how sure are you that this was NOT the problem you have now? It maybe that the problem went away for a while and is now back.

Increasing target margin should make you more immune to noise spikes, but only if the margin is high enough that the spikes leave some usable signal, in your case the spikes are bigger than the target, so its not helping.

Time to power down the house, and have just one mains plug to run the modem and a laptop running off battery to test it. Then see if the situation improves.

Also any chance of a longer plot, as the time shown is just around sunset, at the point where security lights may be flickering on, and they are great RF noise producers, and the sun setting increases the amount of noise affecting ADSL too.

Have you done the basics - i.e. checked for noise on the PSTN line and tested using the test socked with no other equipment connected??

I've checked the basics and this line is only used to ADSL, so there's a faceplate with the router and a single handet (which I forgot to mention but it was also replaced last June) with no extensions.

I'll try and get a longer plot this evening.

I know I'm repeating what I said above but when I was on a 6dB SNR margin, the internet was intermittent but the router never ever resynced and TT could see that there were errors but since increasing the SNR margin which they hoped would get rid of the errors it's just made things a whole lot worse.

I'm currently on a SI158M1M (or something similar) profile which has made the line unusable but I was previously on SF624M1M where I'd have intermittent slow downs and pauses but the router never ever resynced.