Hi and welcome
>> My Netgear DG834 sync's at 8128, sometimes a bit lower at night
>> the BT test says I'm set at 6500 kbps at present
The 6500 profile is based on your lowest sync speed, therefore that implies that at some point your router has synced anywhere in the 7392 - 7936 kbps region
>> best d/l speeds are about 5000 kbps, dropping to about 1400 kbps
Sounds possible Im afraid.. evenings are when adsl experiences the most contention because more people are online and using it.
Ive been through phrases of bad contention myself several times in the past - in fact its probably the reason why I first became so interested in finding out how adsl worked.
Believe it or not, but BTw define anything over 400kbps as acceptable for a home connection because IPStream adsl is a shared resource.
When I first got "maxed" I was seeing speeds in the region of 6-7Mb, since then my speeds have gradually reduced as more users are maxed - in fact at the weekends I was seeing speeds under 1Mb and there was nothing I could do. Aside from the fact that Id carried out BTw speed tests and knew that it wasnt my ISP.
However there is some light at the end of the tunnel, my exchange was evenutally marked "red" a few weeks ago.. and since Monday Ive been getting good speeds again - so BT has hopefully put more bandwidth on the backhaul.
Theres more information about
Acceptable Speeds.
>> it did not make any difference to the Noise Margin but I wlll try it in the evening too
Evenings is when your SNR Margin is most likely to drop for various reasons.. when your SNR Margin is lowest then thats obviously when you will sync at the lower speeds.
>> is the low evening Noise Margin likely to have much effect on speed both actual and the BT configured speed?
Yes it will affect your sync speed, if theres insufficient Margin, then you get a lower sync speed.
Secondly, when the SNR is lowest, its when you are the most likely to get lost packets... therefore your router has to re-request this data, which makes actual throughput slower.
Im not sure if the later is true in your case, but if your router shows lots of CRC/HEC errors then it will be a contributing factor to slower actual throughput speed.
>> Can BT improve the Noise Margin at their end?
Not really* - Noise margin is how well your router and the dslam at the exchange can *hear* each other. If youre on a long line, then there isnt really much anyone can do about that. The further away from the exchange you live then your signal weakens.
There are a few things that you can perhaps try and do to improve SNR Margin on your side. Theres some tips to help try and improve
low SNR here.
*Unless there is an actual fault on your line, such as worn line
If you want to provide your line stats (sync speed, SNR Margin and Attenuation), then someone can perhaps look at that and see if things look normal.
Unfort Im not going to be around for the next few days.. but one of the other guys should hopefully pick up on them.