I've exhausted all other avenues so I have come to hopefully find some people who know more about ADSL than me (I'm an IT Engineer that deals with broadband quite frequently)
Basic information, I am on the Sky Unlimited broadband package and have been for over two years. I have had significant problems with my speed from the start.
To cut a long story short, I am currently synchronising at 1.9 meg with the following line stats:
ADSL Link Downstream Upstream
Connection Speed 1952 kbps 768 kbps
Line Attenuation 62.5db 31.5db
Noise Margin 7.6db 7.0db
Things I have tried so far (all tests done directly into BT Master Socket)
1) Tried 3 seperate routers (Sky provided router/Netgear DG834/Draytek 2830)
2) Multiple different filters on the line
3) Multiple different RJ11 cables
I have raised this multiple times with Sky Broadband (albeit not in the past 6 months). They have tried retraining the line/setting a manual profile on the line.
I am approximately 3km from the exchange according to http://www.samknows.com/broadband/exchange_mapping. This also has an estimated speed of 3.5Mbps. If I run through the broadband checker on Sky's website, they advise a speed between 2.7Mbps to 7Mbps at my address. O2 Broadband reckons around five. I have never had a sync speed over 2.0Mbps.
I also happen to be living directly next door to family (who are 10 metres away). Their line attenuation is 45 and they have a sync speed of just under 7.0Mbps.
It's incredibly frustrating as I quite often work from home and it's like wading through treacle. Knowing that literally 10 metres away from me someone is getting 400% my speed is incredibly frustrating. I suspect the key here is the attenuation. Where the BT line comes into my property I have something additional on the end of my line that none of the other houses in the street have. I've uploaded a diagram here:
I have had BT Openreach out to this issue once. He checked the line over and because the line was stable and his tests didn't show any issues he refused to do anything. He is right (the line is stable) but it is ridiculously slow!
Any help/advice anyone could put my way would be so appreciated.