VDSL2, Sync & SNR....

[jm_paulin]

Just curious about SNR reported by my shiny new 2850 when using VDSL2.

Rebooting my modem at 8am, I get a SNR of 70/62 (Upload/download), and a sync of 19999/70510.
Rebooting my modem at 1pm, I get a SNR of 148/61 (Upload/download), and a sync of 19999/70166.

So as I never unlocked the BT Modem, I do not know the values I had, but I would expect a higher SNR to give me a better sync, not a lower sync...

I have no other values to compare with, so I am not sure what to make of these. How does this compare with others?

[Glenn]

It maybe the max your line can support, but is capped at 80/20.

[Steve]

I'm assuming there's a decimal point missing and looking at the figures the increase in upstream SNR is of no benefit as the cap is at 20. The downstream snr has fallen slightly and so has the sync.

[Lance]

The downstream snr has fallen slightly and so has the sync.

Which is the opposite of what would normally be expected. Mind you, given the difference I wouldn't worry about it at all.

[Steve]

I agree the difference is insignificant. In this situation I assume the ambient noise level was slightly raised from previous so the sync was reduced to maintain the same margin.

[Ardua]

My stats from a Fritz!Box 7390 modem/router are attached. The SNR on 40/10 was 15 and it dropped to 11 when I moved to 80/20. Looking at my statistics, the downstream SNR is pretty much a straight line.

[Polchraine]

From 0800 to 1300 I would expect either the SNR to improve, or where there is a dynamic system in place for the sync to increase whilst keeping the SNR constant +/- 0.5 dB.  Mainly because atmospheric noise continues to drop from sunrise through to late morning.

However, yesterday from late morning there were a large number of thunder/storm clouds around - even if there is no lightning or thunder there is intense electrical activity up there and that would force the SNR down - I have seen drops of 3 or 4 dB.   So, what might have happened is that the SNR dropped to say 5.0 dB,  the modem decided a resync was needed, at achieved that with 6.0dB and the 6.1 is just a little drift away.