ADSL intereference - a pattern emerges

After ~2 weeks of recording it seems an ADSL drop consistently occurs around 21:40 +/- 5 mins each night. This has conisistently happened over the last 5 nights or so - this is where my speed will get knocked from a min of 3500 down to ~ 1700, yet within minutes the noise on the line reduces.

So I could be on to something. A colleague suggested a local "balancing pond" - could it be timed pumping activity? Is it when street lights go on (I need to check). Could it just be something at a neighbours on a timeswitch? A local electricty substation? Something in an industrial estate....

one step forward at least !

Accepted for Brittanica online

Just a quick update, but my application (as a publisher) for Britannica online was accepted, so I'm now fully signed up. Will take a look around..

Britannica online

Brittanica have recently announced their "webshare" initiative - an effort to encourage websites to link back to brittanica content. It will be rather interesting to see how this compares the most sites current use of wikipedia (warts and all).

Each source has their pros and cons, so having access to a combination of the two should be somewhat valuable, although I have to admit wikipedia is my favourite.

ADSL interference

Interesting I just came across someone describing a nightly increase in noise with their adsl (see it here)... it reminded me to write about my problem... I'm trying to track down what I think is noise in the 300-550 kHz range .. that's outside traditional LW/MW.

I'm about 5km away & get synced at 3600-4700 normally. This gets worse towards evening with probably a drop in SNR (at fixed speed) of ~4dB tops

But sometimes I get blasted such that my modem will resync to 2800, 2400 or today as low as 1700. This blast lasts anything from a couple of minutes to say 2 hours, although typically is 20-30 mins.

Once this stops I keep the same rate but my SNR shoots up to anywhere in the 15-21dB region.

So annoying -- I know do a nightly dsl reset, but I also noticed the "bin allocation" graph rather than gradually tailing off at higher frequencies I get a very significant (some bins missing) depression at around 300-550 khz which goes away when the interference stops.

I'm already filtering at the master socket, and have eliminated most electrical equip in my house. I'm clutching at straws now and thinking, could it be mains-bourne interference, would some mains filtering help? Should I plug the power adapter in somewhere else... but it's the timing and freq hit that's wierd. So there's a main transformer a few doors down, streetlights outside (but they're on far longer)... it does seem to happen more at weekends and after school. Radio ham perhaps? but presumably their transmissions are well "focussed" RF wise?

You can see an example picture of the depression here whilst an example of normal behaviour is here
Ideas very very welcome!