0.5dB is not significant in my opinion. Whilst it may be a good percentage of the SNRM at your "full speed" it is little compared to the full noise margin available - if you forced the line to 512Kb then the margin would be a lot higher and 0.5dB would be a small percentage of the total.
A dodgy power connection means it is right to replace the router but the extra 0.5dB in your original post is not going to make a major difference to speed, even 1.5dB as going to be a relatively small improvement.
I strongly disagree.
I'm currently synced at 69129 with my attainable actually reporting 66996 due to currently having 5.7dB SNR.
That suggests that a loss of 0.3dB would reduce my connection by 2Mbit, which implies 1.5dB could be up to 10Mbit, a 1/8 reduction in sync speed if you are right on the edge of the limit. Its pretty much what HAS happened to my connection over the last few years, unfortunately due to crosstalk so not fixable.
Granted its probably not so linear in the real world, but I'd still argue its likely to be far from a "small improvement".
As it stands I'm keeping synced, but a sudden loss of 0.5dB and certainly 1.5dB could cause a resync. That alone is hardly an insignificant impact on your connection.
Edited by alexatkin (Mon 26-Nov-18 15:41:57)