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If it's stable at 6dB then it should be ok.

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It is now with the SpeedTouch 585 but not with my old Billion hence the reason why I asked to have my SNR raised to 9 dB a while ago!

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Mine runs for weeks at 6dB without dropping sync & has been know to drop to 4dB for days without problems.

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My SNR drops to around 4 dB every evening but always recovers to 6 dB through the day.

If my SNR was lowered automatically to 3 dB by BT's DLM then I know my line would get unstable as the SNR would probably drop to 1 dB or lower in the evenings leading to a dropped connection!

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Disagree all you want. ADSL is my job.

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You also, not surprisingly, appear to know the difference between SNR and SNR Margin which your antagonist failed to do - he showed this by quoting a passage about SNR when he was talking about SNR margin.

An SNR Margin of 0 would be marginal. It is the boundary between a negative value which won't work (by definition) and a positive which will. Having a positive value of 6dB gives a margin or error which is liekly to be enough in most circumstances - it means that the measured SNR is four times the minimum acceptable SNR for the channel.

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It is now with the SpeedTouch 585 but not with my old Billion hence the reason why I asked to have my SNR raised to 9 dB a while ago!

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Since the SNR is a measure of the strength of signal compared with the noise on the channel, you can't change that by a setting, only by increasing the signal or reducing the noise.

I suspect that you are talking about the SNR Margin which is not the same and confusing the two is not a trivial matter, causing most of this thread to be meaningless.

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I suspect that you are talking about the SNR Margin which is not the same and confusing the two is not a trivial matter

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Yes you are right, I was talking about SNR margin. Sorry.

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causing most of this thread to be meaningless.

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However I don't agree with the above.

speed increased but became unstable and has been dropping back to 1mb ever since, my router lost synch several times my noise margin keeps changing from negative to as high as 9db. During the 10 day training period when the MSR is found does that mean that at the end of the training period the MSR is the maximum speed I will get, or is this the minimum.

Whatever your line is syncing at (exchange contention and ISP contention permitting) you "should" get. So if you sync at +6000kbps you'll get around 600kb/s for example.

The problem I've found moving to MAX over fixed (I'm on my 10 days now too) is when it loses sync just once, it automatically drastically lowers your sync rate and it takes absolutely ages for it to go back to the higher rate (if at all).

The reason this is happening for me is that whilst I have a superb line during the day, it gets noiser at night and regardless of speed (it happened when I was on 2mb too) it loses sync occasionally when the router can no longer keep sync.

I initially synced at 7776kbps and was getting 770kb/s, but 4 days and just 3 loss of sync's (which my router did recover from without disconnecting anyway!) later I'm at 6528kbps and getting 650kbps.

I've also discovered my line is interleaved, which means pings to jolt.co.uk are around 40ms instead of the 20ms they were when my line was fixed.

Ideally i'd like my line to just sync permanently at 7776kbps and be on fast mode, regardless of how often the router loses sync, but this being MAX that aint gonna happen.

So am I right in thinking that after the training period speeds become dynamic for instance one day I could get 1.5mb the next could be 3mbs? So long as it does not fall below the fault threshold

It'll fluctuate the sync speed training to maintain the maximum, after 10 days it locks at that sync. That's your maximum speed you'll see. Best time to check it is around 12pm for speed.

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after 10 days it locks at that sync

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Sorry, but that's not true. BT are quite clear on this - the only thing that happens after 10 days is that the system makes a note of the sync speed as a reference for customer service to compare against if speed issues are reported in the future. That's it. The modem continues to sync at the highest speed it can whilst achieving the target SNR margin. Max continues to monitor the line and adjusts the target marging and interleave settings if appropriate. The BRAS IP profile continues to be adjusted in line with the sync speed.

Agree with most of your post, but the target SNR margin is set during training, thus limiting your re-connection maximum sync speed. And:-

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Max continues to monitor the line and adjusts the target marging and interleave settings if appropriate.

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That doesn't seem to be true in practice, even if it is supposed to be. Otherwise, why would we need the DMT, and why do ISPs have to be kicked and dragged to get BT to reset the SNR Margin, and remove Interleave?

Edited by RobertoS (Tue 13-Mar-07 22:20:09)