I had this problem last winter and bought a new router, never solved the problem, and now this winter it's back. Tiscali say it's my fault, but with a new router plugged into the BT test socket, I still get the line drop. The best SNR I get is 6db, but the new netgear a few weeks ago will hold the line down to SNR of 4 but after that it drops. The problem is worse at night, but the rain seems to be the main cause, getting anyone to listen though is a real problem.

With current rules they can simply say

a) Put up with it
or
b) We will mark the line as not suitable for ADSL

There are no requirements to fix or make good ANY faults that affect ADSL, even under the proposed USC they are likely to be get out clauses, as it won't be a legal right, and BT will not be the sole USC provider.

wow, thanks. basically it was put up, but now emailed them a 3- speed test results taken using this site, and the speed varies from 195Kbps to just over 1100Kbps on a good dry day, same time, just change in weather. Summer is fine, and so is the dry winter, so the line will clearly support an ADSL signal, at a reasonable speed, even though i'm 3.75Km from the exchange

In reply to a post by MrSaffron:

With current rules they can simply say

a) Put up with it
or
b) We will mark the line as not suitable for ADSL

There are no requirements to fix or make good ANY faults that affect ADSL, even under the proposed USC they are likely to be get out clauses, as it won't be a legal right, and BT will not be the sole USC provider.

That's not strictly true. Earlier this year the residents of this road were so fed up with the appalling service that we got with ADSL, which was degrading all the time, that we lobbied the CEO of BT and threatened a lot of bad publicity, and eventually they replaced over 500 metres of faulty cabling in this road. Although this resulted in dramatic speed increases for all the residents, we still get noise fluctuations which pull the speeds down. However, the difference is that I was getting 2M which often dropped down to 1M, and now I'm getting 6.5M which drops down to 5M.

Note the use of can, not will.

In reply to a post by MrSaffron:

Note the use of can, not will.

I agree, but you appeared to give the impression that there was nothing that the OP could do about their problems. What BT want to do, what BT are obliged to do, and what BT will do if threatened with bad publicity are three completely different things.

This week on the Gadget Show (where TBB got a mention incidentally), they had a feature on how to complain, and this included emailing the CEOs of companies, and in my experiences (not just with BT) this appears to work.

Got to agree with Zebedee and Kijoma here, PhilipD is living in cloud cuckoo land if he thinks RF doesn't interfere with ADSL.... We've had about 18 BT engineers and a REINS engineer trying to diagnose our fault for the past 18 months, exactly the same problem it drops out at night, but through the day it's up past 3.3Mbits....

The BT engineers always comment on how loud the MW stations are blasting through on their BAT phones... it's true.... twisted pair does cancel out interference but that is for a perfectly balanced pair... in other words if an spike/amplitude arrives on one leg the opposite amplitude/spike will arrive on the other thereby cancelling it out .... but it's rare for a telephone wire to have "exactly" equal lengths and of course any residual will appear across the terminals for the modem to deal with along with all the pops, cracks and whistles that a phone line receives....

As most of us know ADSL uses frequencies from approximately 26 to 138 kHz for the upstream and 138 kHz to 1104 kHz for the downstream connection although this range is extended for ADSL2 connections, and some VERY powerful transmitters are in that range, plus they are amplitude modulated which would spread them very wide off the centre carrier frequency in comparison to an SSB transmission or CW (morse) transmission...

This is all tied in with what the sun is doing, high levels of solar activity increases reflection, refraction, diffraction, absorption, polarization and scattering, which is why when we did long haul communications on HF (High Frequency) in the Royal Signals, we had to predict what the conditions would be, because even in the 1980's the Army was sending digital signals over both HF and VHF way before digital took off in civvy street ... propagation is highly variable, some days you'll get very little propagation other days you'll hear stuff from the other side of the world.... There isn't a modem on the market that can filter out that kind of variability of interference/signal.

Tune your AM radio to around 612Khz (about mid band for ADSL1 ) and put it next to your modem, you should hear the rhythmical beating of the modem with very little background noise, then try it again when your modem is having difficulty keeping its speed..... you'll be surprised at how different the modem sounds during the night when it's working harder

Btw I'm ex Royal Corps of Signals long haul communications specialist, and 23 years in Analogue/Digital component repair with computer and communications equipment .....what I don't know about interference over communications lines/airwaves you could write on the back of a postage stamp with a bingo marker pen ;¬)