slowly degrading adsl max??

norm · 21 May 2006 at 10:42

csmager said:
Stability's a measure of how long the line remains synced, not a measure of the SNR margin. Even 3dB could be perfectly stable on some lines, but it's hardly a sensible place to start. 6dB is the default setting, and that's what everyone's Max line is set to on Day 1.

Why should 3dB or 6dB be any less stable on other lines? Surely it's dependant on the modem at the other end and how it's able to manage the signal.

My debut on MaxDSL began last Friday and it initially started out at a 7136000 bps sync rate @ ~6dB. Day later I was bumped up to 7168000 bps @ ~5dB. The error rate is significantly higher now but the line hasn't dropped in 24hrs.

So I don't know what the BRAS system at BT will make of that.

csmager · 21 May 2006 at 10:45

norm said:
Why should 3dB or 6dB be any less stable on other lines? Surely it's dependant on the modem at the other end and how it's able to manage the signal.

As an example, my line is unstable at 6dB. This is (most probably) due to the fact my internal wiring runs next to a load of other internal phone wiring, and the master socket is right next to the ring generator for the PABX system. Basically, when the phone rings it creates a load of noise - more noise than a 6dB margin is able to cover up, so the line drops.

norm · 21 May 2006 at 10:50

I guess SNR is fairly meaningless then if you account for random bursts of interference like you are experiencing.

csmager · 21 May 2006 at 11:05

norm said:
I guess SNR is fairly meaningless then if you account for random bursts of interference like you are experiencing.

It is a bit. Same with everyone though - in an ideal situation with no random noise bursts at all, and SNR margin of 0dB would be fine.

It just depends what the noise sources are, and how large they are as to whether your margin is big enough - hence the DLM being there to add more when necessary.