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Curious about noise margin and line attenuation

Anonymous — Fri, 20 Jan 2023 10:25:36 GMT

I have had a few issues with my line disconnecting over the last few months, the first culprit being a waterlogged underground access hatch.

But after a solid week the drops have returned (17 disconnections yesterday was a new record), so Openreach are due again on Monday, plus I have had a new Smart Hub 2 just in case. Touch wood the connection has settled for the last 17 hours bar a disconnection around 4 hours ago.

I pay for Fibre 2 because I would like to access the higher upload speed which my line is supposedly capable of handling, but alas no one at BT will actually put me on that profile.

As I have had issues I have been looking at the stats I became curious about noise margin because after looking through the forum I'm not sure what is good or bad?

When you look at noise and line attenuation, is the first number in the hub the actual and the second the target or vice versa? Is a higher or lower number preferred?

Just curious and trying to learn because we are not on any FTTP upgrade plans so stuck with copper for many years yet potentially.

Hub Stats

Re: Curious about noise margin and line attenuation

imjolly — Fri, 20 Jan 2023 10:27:21 GMT

I would turn FTTP mode to off and get use of ethernet port 4

The line attenuation give indication of distance from the street cabinet and lower the closer to cabinet the faster your speed. the normal noise margin is 6db. yours is just below that as your actual speed is slightly faster than your attainable speed.

Re: Curious about noise margin and line attenuation

Anonymous — Fri, 20 Jan 2023 11:18:44 GMT

Brilliant, thank you.

I forgot about the FTTP port setting as well so great reminder!

Re: Curious about noise margin and line attenuation

licquorice — Fri, 20 Jan 2023 11:20:59 GMT

The figures are actual for upstream/downstream

Re: Curious about noise margin and line attenuation

Anonymous — Fri, 20 Jan 2023 12:00:46 GMT

@licquoricewrote:
The figures are actual for upstream/downstream

Thanks

So a Noise Margin of 11.5 / 5.1 is:

11.5 on the upstream
5.1 on the downstream

Is that correct?

Re: Curious about noise margin and line attenuation

licquorice — Fri, 20 Jan 2023 12:06:38 GMT

Correct. As your upstream is capped at 10M but your attainable is 17M you have a high noise margin.