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Following up on my previous post, it seems I have now achieved a stable connection. Emphasis on seems as I still want to wait and see how it holds up next weekend because drops are worse on Saturdays.
There was nothing wrong with my cabling as I switched, swapped, shortened and tried everything to improve that last Saturday and still got dc’ed about once every five minutes.
The magic trick turned out to be lowering the downstream in my profile. I’m supposed to have 8Mbit downstream, but at that speed I have a downstream signal to noise ratio of 6dB, which is bottom of the barrel. Add a crappy line, other people using equipment during peak hours and poof, there you go.
However, letting the provider switch the profile and set it back to 4Mbit boosted the SNR up all the way to 24dB. I then told them to set it 6Mbit and seem to get a comfortable 16dB, which should still leave me more than enough of a margin to handle peak hours.
I hope it holds up this weekend, and then I can start complaining about paying too much for a 6Mbit connection. ;)

After our move the adsl internet connection has been less than stable. Sometimes it’s up for a week, sometimes it disconnects 20 times a day. According to the isp this is due to us being 4km from the exchange, which is kinda weird as we only dropped a floor and never had problems before. So now I’m reading into things like line attenuation and dB signal to noise ratio so I actually measure what the hell is going on and if any improvements I make to the indoor cabling have any effect whatsoever. Now if only the cable isp didn’t block certain server ports I’d switch to cable in a heartbeat.

A high SNR (signal to noise ratio) simply means how loud the signal is over background noise. The higher the SNR margin the more stable the connection. You have a strong signal and have plenty of head room to receive faster speeds. Generally you would have a high SNR if you’re on a restricted speed plan eg. 256/64, 512/128 or 1500/256. The faster your connection speed the lower your SNR will be. Generally on unrestricted speed plans like Adsl2+ up to 24mbit the isp will set the SNR margin at which your modem connects generally a range between 6dB to 14dB. This will give you the fastest speed while maintaining a relatively stable connection.
Attenuation on the other hand is a measurement of the resistance to the signal on the line and should never change regardless of speed.

There are many factors which affect both SNR and attenuation. A few are line distance, gauge or thickness of line, quality or age of line, number of bridge taps on line etc.

So now I can start focusing on the latter, one step at a time, as the inhouse cabling is the only thing I can influence myself. And if that doesn’t help… time to start thinking about cable after all.