Why is my sync speed changing?

[tehidyman]

My phone line exhibits variable and often excessive noise.  When connection is lost I reconnect at a lower sync level and therefore a lower profile.  In the past, unless I reboot, the sync speed and the profile have not changed.  Recently I have noted that my sync speed has moved up from 2880Kbps to 5056 in several steps over about 12 days.  My Router Statistics indicate that my LAN has been up for over 460hours which I assume means that I have not had any reconnections.  I am delighted that I am currently getting a test download speed over 3.5Mbps, but wonder what causes these changes.  (All information gratefully received)
I am on IDnet's up to 8 meg service, have a Netgear 834Gv3 router and on the Camborne, Cornwall exchange.

As a postscript I should add that over several months I have done everything recommended to reduce noise with no apparent success

[Rik]

LAN uptime is just the amount of time between router reboots, it's the WAN uptime which is more significant.

What we need to know if what your current downstream sync speed, noise margin and attenuation are. Ideally, if you have the same information from before the improvements, that would be very helpful.

Pure speculation, but it may be that BT have renewed some cabling or equipment at your exchange.

[tehidyman]

LAN uptime is just the amount of time between router reboots, it's the WAN uptime which is more significant.

What we need to know if what your current downstream sync speed, noise margin and attenuation are. Ideally, if you have the same information from before the improvements, that would be very helpful.

Pure speculation, but it may be that BT have renewed some cabling or equipment at your exchange.

Current WAN uptime is 290hr+, Download Sync 5056Kbps, noise margin 5-6db, attenuation 53db.

Looking at some earlier notes download sync speeds varied from 1388, 1868, 2880 with noise margins from 0 to 12db, and yes the connection was often maintained at 0 margin.  I was running Routerstats some of the times. Attenuation was 51 to 53 db

Can sync speeds change without rebooting? On Monday it was 4640 on Tuesday 4800 and today 5056Kbps.

[Rik]

Usually a reboot is required. It looks as if BT have lowered your target noise margin from 12db to 6db. That would produce 1-1.4M of extra sync speed, more if the line noise has improved too.