Noise margin has fallen to 3.1db down.

[#1]

Hi All,

My router's noise margin has been falling over the last week to a "good" figure of, currently, 3.1db down. I say "good" as I understood that as it fell to 3db my speed would increase. Not so, as my maximum data rate has been falling too and my speed at the router has remained the same throughout.  How and when do I get to see a higher speed? Am I missing something here?

Any info gratefully received.

John

[#2 · Accepted solution]

If the noise level remains constant then the speed will increase up to the preset maximum limit as the DLM reduces the SNR . When the speed limit is reached the SNR will remain constant. The minimum SNR is generally set to 3dB. 

If the noise level increases then the SNR will again drop. In this case the DLM will reduce the speed to maintain a minimum SNR of 3dB.

Unfortunately it looks like you are suffering from the second scenario.

[#3]

Thank you for that info. I now understand what is happening.

Cheers, John