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Setting the Noise Margin, a catch-22?

fishrow
Grafter
Posts: 67
Registered: ‎31-08-2009

Setting the Noise Margin, a catch-22?

I believe the SNR Margin has one of the higher "weightings" in relation to other stats parameters for influence on stability and speed.
Some recent posts indicate the margin varying and dropping below the "magic"  6db causing issues with sync loss and speed.
I've seen Joanne Pilson mention "setting" the margin for people. I think I'd like mine set to 9db, as some recent sync probs diminished when I saw that figure in my router compared to when it would show 6, then drop lower and lose sync.
But there seems to be a catch involving the DLM at the exchange hinted at in one of the posts.
It _always_ wants to work with a figure of 6db it seems, or, no matter if stability shows up for a decent time with a figure of between 8-12 say, then it re-tries to impose the 6db and the cycle of probs starts again.
As a further thought. I appreciate that some spurious noise burst will upset things perhaps, so what happens there?  Does the router end see that burst and changes the SNR margin and the DLM then makes its changes, or is it the DLM that responds first and makes a change?
Can Joanne or anyone clarify that point and confirm/deny the catch-22?
thanks
3 REPLIES 3
ReedRichards
Seasoned Pro
Posts: 4,927
Thanks: 145
Fixes: 25
Registered: ‎14-07-2009

Re: Setting the Noise Margin, a catch-22?

Quote from: fishrow
I've seen Joanne Pilson mention "setting" the margin for people,,,

No. that cannot be done.  The best Plusnet can do is reset the DLM to retrain, which will cause the noise margin to start at 6 dB in the first instance
Quote from: fishrow
As a further thought. I appreciate that some spurious noise burst will upset things perhaps, so what happens there? 

In principle if that happens enough and is bad enough then the DLM will increase the noise margin to 9 dB and will keep increasing it in 3 dB increments until the problem goes away.  The catch 22 is that if some other or temporary cause is mistaken for a noise burst then the DLM is very quick to increase the noise margin and very slow to decrease it again once the line appears stable.
Epyon
Grafter
Posts: 285
Registered: ‎31-03-2011

Re: Setting the Noise Margin, a catch-22?

Some routers can set the SNR
Heres my rocking at 0.8 Wink
ReedRichards
Seasoned Pro
Posts: 4,927
Thanks: 145
Fixes: 25
Registered: ‎14-07-2009

Re: Setting the Noise Margin, a catch-22?

Quote from: Epyon
Some routers can set the SNR

Only, I think, by telling fibs to the DLM.