I can assume that more lines have been activated, to date, but is the drastic fall of SNRM normal ?
Unfortunately its something all us have seen
I wasnt one of the first on my cab so I will have escaped the worst jumps, but even so over the past year my experience is that Ive lost circa 20Mbps of headline speed. Most of the dramatic decreases were in the early months and ['sacrifice to the DSL Gods made'] it has levelled off more now. I do still see a slow decline every so often of the loss of another 500kbps or so.
To compound matters I developed a HR Line fault a couple of days after placing my order for fibre, which also affected my first few months on fttc so my early graphs are very messy and hard to see anyhow but my days of max headline being 105 Mbps are long gone
Before I got the Zyxel in March I was down to 86Mbps using the HG612.
The ZyXel took me back up to a few kb short of 90Mb.
Im now at 88.7Mb on the Zyxel [or 82.5Mb on the TD-W9980]
What is it ?
Its called cross-talk or FeXT.
Its not contention, its when other lines cause noise on your line (hence why your SNRm suddenly drops like youve seen).
These lines are known as disturbers... and some lines cause more disturbance than others. Just about everyone of us on here has seen it.. we notice and say to ourselves - there goes another line being added to the cab.