SNR Fluctuating a lot.

I have been having a problem for the last few months with speed on ADSL varying from 850Kb to 2.4Mb. The line has been stable at 2.4Mb for the last 7 years.

There have been various Openreach engineers out but they cant find any problems.
Here is a graph of the SNR and Sync speed over the last few days.

SNR Graph

There are sudden drops to 0 SNR and then a resync and the line goes from around 2Mb to 1,0Mb,

The line then continues at this speed with a 9dB SNR until a sudden jump of 5dB takes it back to 14dB SNR and then a resync takes the sync speed to 2.0Mb

I have all equipment at my end disconnected apart from the modem, also a new V3 Openreach master socket was fitted so I can't see any problem at my premises.

Does this look like a common issue that could be easily spotted or is it a nightmare to find?

Have verified that test socket does same and unplugged other electrical devices from mains

Are you using a netgear dg834g or netgear router?

Mine often used to hit 0db noise margin, whereas other makes stayed between 5.5 and 6.5db.

Yes, currently plugged into top outlet of a NTE5 MK3 which has been replaced twice. Nothing else plugged into lower section.

Have even tried plugging the modem into a mains extension socket from another room.

I have tried the TalkTalk DSL-3680, two Thomson 585V6s and a Billion 7800DXL, all with similar results.

I am only able to log the SNR with the Thomson using the DMT software.

I had a similar problem a few years back albeit I have a slightly better top speed than yourself (a massive 4mb).
The SNR graph when plotted was like a sine wave up and down all the time with a 5/6db variation all the time.
After a lot of calls etc I eventually had a BT guy come out and in the end he re-routed my line and it fixed it - it made it slightly longer but was stable - he couldnt figure out what the issue was, just a dodgy bit of wire somewhere in the route.

So I have been having this problem for ages and as soon as I post something on thinkbroadband the problem seems to have settled.

The SNR has been stable at 9dB for 21 Hours and looks like THIS

So if they put me back to a 6dB profile I should be back to where I was in February

Maybe they fixed someone else's problem and it fixed mine as well, there were Openreach engineers in the area on Saturday.

A high chance that a source of random noise has just been switched off, next time its get a battery AM radio and look a bit silly to spot where the noise is worst

http://www.thinkbroadband.com/videos.html video may be about Christmas lights but principle is the same for any interference source really

I spoke too soon

It now looks like THIS

Switched power off the entire house and used a UPS to power the modem, no change, looks like it is external, time to take a drive down the line.

Edited by onthenet (Mon 13-Jul-15 19:44:46)