Just for information my adsl is 20CN, which I'm told by the engineers is harder to setup than the later versions. But now its fixed.

Anyway, JL/Plusnet ran some more tests and confirmed that my sync speed was about 6300 and the SNRM was about 12.1. Also that my profile had been set to 5500. This didn't explain the poor throughput of about 2000 so they arranged for an engineer to visit.

He came this morning and tested the line and found no problems but confirmed the poor throughput and the same numbers I'd got as above.

He said the SNRM should have been 6 and since I was set to 12 this explained the lower sync speed and lower profile. He called BT and got this changed to 6, which took some time to do. I'm told its a manual process.

Once done the SNRM became 6 and the sync speed became 7840, which resulted in a higher profile so I should have got a throughput of about 6500. However, we were still seeing around 2000.

He then said that Plusnet also have their own profiles and contacted them and found it was set to about 3000. He requested this be changed but in the meantime he took my router to the exchange and set up a local connection there and eventually got the download speed of over 6500.

When he returned with my router the download speed when using his laptop was still around 2000 but he noticed that the ethernet cable connection to his laptop was a bit loose. We tried a wireless connection and he got the 6500 we were expecting. The cable connection problem was really a red herring because it's a spare and not one I was usiing for any of my tests.

I connected up my main machine and ran tests and its now back where it was three weeks ago - so a result.

There is no explanation of why the SNRM was dropped to 12 and no explanation of why Plusnet had dropped my profile to 3000.

In reply to a post by Spuriousfish:

There is no explanation of why the SNRM was dropped to 12 and no explanation of why Plusnet had dropped my profile to 3000.

(and from previous post)

In reply to a post by Spuriousfish:

FWIW:
Rx Sync speed is 6240kbps when it usually runs just under 8000
RX SNR is 12.1 when it's usualy around 6
Line attenutation 31/16 - cant remember what it usually is.

With ATTN like that, you should be getting sync of 7-8 Meg imo. While your SNR is usually at 6, if line quality allows for it, it can be dropped to 3. See my 'best effort' results image here:

http://www.camieabz.co.uk/broadband

Similar ATTN, but downstream SNR set to 3.

In addition, I would harass PN support to reset the profile, and have interleaving switched off (a.k.a. FastPath). When on older ADSL my profile would be 8192 or 8000. Forget which.

Worth nothing that restarting too often will result in slower connection, so request a profile reset, interleaving off, and if your router allows for it, set downstream SNR to 3. The reset might take a few days, and that will allow for things to settle. If your line isn't up to supporting 3db, it will reconnect at 6db.

Thanks for the reply.

As stated in my previous post, once BT and Plusnet reset noise margin and profiles my sync speed became 7936. This is giving me a download speed of approx 6200, which I'm quite happy with.