DMT Tool noise margin query

I haven't been using the DMT Tool for long and I'm confused as to how it works regarding the target sound margin.

If I revert back to default SNR (like now with the option ticked as in my screenshot) then my router syncs too high at around 4.4 Mb which isn't enough for a 4 Mb profile as I need at least 4544 and this can't be achieved without lowering the noise margin.

http://i14.tinypic.com/47illx1.jpg


If I reduce the target margin to only 1 or 2 markers above the minimum setting then my SNR stays at 3.5 dB all the time i.e. in the evenings as well where my SNR used to drop at these times

My query is how come the SNR doesn't alter (i.e. drop in the evenings due to increased 'crosstalk') when you manually tweak it as opposed to letting BT's DLM handle it?

p.s. I'm happy with a 3.5 Mb profile and would like to get a sync rate at 4 Mb or slightly above as opposed to the 4.4 Mb+ sync that I have now as this just introduces more noise into the signal without increasing throughput.

From the situation you show in your picture uncheck the default then drop the slider by one division and apply/resync. You may find that the SNR margin drops to 6.0 and your Downstream bitrate creeps high enough (over 4544). If not, repeat with just one more slider division - it really is that sensitive. Alternatively go up a division at a time to get higher SNR margin and lower sync. I find it can take a couple of resyncs a division at a time before I have the exact balance I want. Then click save settings. Sorry if you've tried all of this before, but it works for me - my SNR still varies by 1 or 2 dB over the day but at a slightly different overall level to the default.

Edited by deleted (Sat 10-Feb-07 18:02:58)

In reply to:

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If not, repeat with just one more slider division - it really is that sensitive.

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Thanks that worked.

I still don't understand why the SNR varies much less than when at default but it's not important.