So - just to make sure I have this right. Ideally you want a low attenuation figure (loss over line) but a high Noise Margin figure (headroom between noise and signal levels).
Right ?

Over the day, and using routestat program, I'm averaging 12 or 24 or 15 for RX Attenuation. I phrase it like that because I'm getting a lot of short "noise-bursts" which cause disconnects (and in most cases I by taking the router out of the test socket and replacing with a phone I can hear significant noise which then stops after a while). After each disconnect the router can reconnect but may give a different RX Attenuation figure.

I'm getting 6k to 8k RX Sync, again interrupted by the disconnects.

RX Noise Margin is ALWAYS less than 10, usually less than 6.

So, if I have understood it correctly, the above means that my line is basically ok (based on Sync and Attenuation) but there is a high background noise level and the "noise-bursts" kill the connection on a frequent but irregular basis.

Any comments ?

I'll keep you posted as to what BT say on Thursday and thanks for your help.

Just installed filtered NTE5 faceplate from ADSLNation. No change I'm afraid, well I guess the downstream Noise Margin is a little higher, hovering around 6.5 to 7. Speed test on here shows only 3.3 Mbps.

I think I have enough evidence of line noise to let the BT guy come on Thursday. Will post update then.

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So - just to make sure I have this right. Ideally you want a low attenuation figure (loss over line) but a high Noise Margin figure (headroom between noise and signal levels).
Right ?

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Thats basically it.

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if I have understood it correctly, the above means that my line is basically ok (based on Sync and Attenuation) but there is a high background noise level and the "noise-bursts" kill the connection on a frequent but irregular basis.

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Not in my opinion. The attenuation should not be jumping around so wildy as that.
Is susspect the reason the noise margin stays around the same is because Broadband MAX is allways trying to connect at the best speed, and in order to attain that it tries to connect at around the same target noise margin, which AFAIK is set to 6,9,12 or 15dB.
I am guessing there is an intermittent line fault somewhere, possibly an HR but there maybe other possibilities.

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I am guessing there is an intermittent line fault somewhere, possibly an HR but there maybe other possibilities.

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The fault is probably at (or very close to) the exchange. The stats show that the underlying SNR is rising and falling almost exactly in line with the attenuation, which is only going to happen if the fault is before most of the noise being picked up.

I have a similar problem thats driving me made.

My connection can stay synced solid for weeks then all of a sudden a get strange blips that drop my sync rate down to 500 - 700k (from about 3.5M). add to this that occassionally everytime a use the phone the sync is lost (and i've tried dozens of filters to rule out a fauly one + my filtered faceplate) then suddenly it will go back to normal.

Done all the standard BT tests to no avail. this is driving me nuts.

any thoughts

First - update on my problems. All seems to have settled down over the last two days, which is actually NOT reassuring. That's the problem with intermittent faults - they never show up when the engineer is here. Actually he did a lot of checking around and did find a couple of things. The box where the line comes into the house had a couple of corroded wires which he replaced. He noticed that the overhead line from the house was rubbing a couple of branches, which I'll take off tomorrow. He's also said that there has been a lot of work going on at the exchange and he's going to ask them to check my circuit out for dry joints. All in all - he was pretty good. There was never a hint of charging me a call out fee, even though he couldn't find a fault on the day. In his view, I had done more than enough to prove that it wasn't my equipment. The key was hearing the audible line noises through a standard phone into the test socket with no extensions connected. Pretty satisfied overall.

Your fault is a tricky one and I wouldn't be surprised if it's also intermittent noise. Read the various posts in this thread. Prove to yourself that it is the line and not equipment or wiring inside the house. Use the routerstats program (it's free - plus it has an alarm when the sync drops) to keep logs of when it drops out. When it drops, rush over to the test socket, plug a phone in and see if you can hear anything.

All in all - hat's off to BT. I wouldn't be afraid to call them.

Your sync rate - presumably you mean you get just over 8kbps ? If you're talking about 3.5M you must mean the speed test, right ?

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Your sync rate - presumably you mean you get just over 8kbps ? If you're talking about 3.5M you must mean the speed test, right ?

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No. My line length is very long so the max I can normally sync at is about 3.5 - 4Mbps.

I'm pretty sure my problem is also intermittant, its just a case of catching it and ruling out everything else at the same time.

Good to hear the engineer seems to have no intention of charging you, thats the one part the worries me.

OK. Good luck. As I say as long as you've taken reasonable precautions to identify that the problem isn't caused by your equipment I don't think they will cause a problem.