Yes I know the evening drop in normal due to atmospheric conditions, street lights, etc. This is happening at random times during the day so that pretty much rules out the above.

It's nothing in my home and it only started after the openreach visit yesterday.

Trust me I'm a Chartered Engineer, no central heating coming on or going off, nothing else on timers in the house, no dodgy light fittings, not even the bathroom fan. I've literally checked every electrical item right down to my motorcycle trickle charger!

OK well a week on and I'm still seeing random rises and drops in my SNR of exactly 0.7dB at all times of the day and night. My Max Attainable Speed rises and falls in line with the change in SNR.

To make matters worse my max attainable line rate is back up at 51Mbps but my actual line rate is now only 42Mbps and falling along with an average drop of 0.1 to 0.3dB per day still.

Openreach have opened a REIN case with them coming to visit this Friday, I did however speak with the guy who will be visiting on Monday and he is convinced, after some initial investigation that it's not REIN. TBH I'd be surprised if it was as I've been told my line was totally clear of REIN, RFI etc. in the very recent past.

Anyone have any ideas? It's definitely nothing in my house, that I know.

God knows what is going on but at least I have someone looking at possibilities now after rattling a few cages.

Well surprise surprise I had Openreach out again, not that they did much mind and apparently it's not REIN. Not that I ever thought it was as my real problems started with Openreach on 11/04/16, not that the Openreach bloke did much either other than suck on his E cigarette!

He told me he was going to follow the route back to the cabinet looking for REIN, he didn't bother, I quietly followed him and he just left!

Still no further forward and my SNR is slowly degrading each day with sudden 0.7dB changes in the downstream SNR at random intervals still.

In 2 days my downstream SNR fell from 6.2dB to 4.6dB, after a firmware update on my Netgear D7000 the SNR was back at 6.2 and then promptly fell again to 4.7dB over night. There is something going on with my connection and I have absolutely no faith at ain in Openreach rectifying the problems they caused in the first place. It does suddenly jump back up 0.7dB at random times but the overall trend is to lose SNR each day that is never recovered without a reboot of the D7000.

After almost 4 months I'm actually worse off than I was before Openreach got involved, they really are totally incompetent!

Know any amateur radio users? reason being, they might be able to confirm interference; the regular-as-clockwork drop and rise in signal would appear to be due to a timer-controlled device somewhere, and not necessarily near you - the range of some interference from baby monitors, burglar alarms, remote-controlled garage doors and the like can be considerable.

If you do know a friendly 'ham', and he can confirm interference, then you can contact OFCOM, who will send an engineer - to confirm - and try to work with the responsible party to remedy/alleviate the issue.

Just a thought.