Hugo Nebula wrote:
Please bear with me: My ADSL router is connected via an extension
from the BT master socket in the hall. The distance to the exchange
is high and I've never got a particularly good connection, but it's
been acceptable at 1Mbps. I'm with UKOnline/Easynet LLU.

Over the last few days the speed and the stability have dropped
markedly. It happened between 6:00pm and 8:00pm on Wednesday. On
phoning my ISP, they said that it could be my internal wiring (well,
they would, wouldn't they?).

Well before you go fussing and fiddling, bear with ME.

In my new install drearily documented in anther thread, I have seen
noise levels and connection speeds dropping at precisely the same times
of day ..my conclusion is that the cold weather is affecting either the
lines, or the amount of electrical noise..from a reliable synch at 4800
a few days ago, post last night the best I can get is 3600..

Its probably loads of CH thermostats arcing and clicking in your
neighbourhood.


Now, how to test that? The bits of kit I have available a a
screwdriver for removing the faceplate's screws, a USB DSL modem, DR
Speedtouch, and a Netgear router. So far, the only results I've been
able to establish with any certainty a
1) when plugged into the socket behind the faceplate, the results from
the DR Speedtouch log are Receive Attenuation=54dB & Receive
Margin=13dB;

Sounds about right.

2) when plugged into the socket on the faceplate and to the extension
in the study, Receive Attenuation=54dB & Receive Margin=11dB;

Slightly better, but not much.

3) currently, according to the router, Line Attenuation
Downstream=58dB & Noise Margin Downstream=wobbling around 12 to 14dB;
4) Connection Speed according to the router=1152kbps, speed test
results currently 965kbps.


that should be OK for reliability..it looks like your line is subject to
burst noise tho, as normally you will synch at 6-8dB SDNR.

Looks like BT has (rightly by the sound of it) adjusted you for a high
noise margin. Or if it's LLU then easynet have.


The current connection is OK, but I had to re-boot the router this
morning to get it.


Its a bit warmer today ;-)

The difference between the logs' margins of 11 and 13 doesn't seem
that great, and AIUI anything greater than 10 shouldn't be
detrimental. Does this indicate that the problem is likely to be on
the BT/LLU side of things? If not, how can I test the quality of my
internal wiring?

I think that in reality there is nothing you can do.

The attenuation and noise sounds like you are several miles from the
exchange, and basically there isn't much you can do about it:

Everyone blames microfilters blah blah blah, but the reality is that
long lines are noisy and lossy and that's that.

I am running reliably at the moment at 45DB attenuation and 7.5dB
margin..that means that my noise spike trigger level is equivalent to
52.5dB 'noise floor' for 3.6Mbps.

You are connecting at a third that speed, so given similar noise floors
you should be able to hit 5dB more..57.5dB..In fact you are operating at
70dB..frankly I am amazed you can get THAT much.

Obviously its worthwhile scraping what you can with top quality filters,
but don't expect miracles.


You noise margin is high, which the ISP can (get?) lowered for you,but
you may end up trading speed for unrelaibility. The longer the line the
higher the margin needs to be.

How far from the exchange are you? Attenuation suggests maybe 5 miles or
so..?