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[alexxx]

The item reported on line number eight, in all of those images, is the Signal to Noise Ratio Margin. When abbreviated = SNRM.

Thanks for spotting me struggling with the description of that! I had a look online and it says a higher number is better but I feel like I've read that wrong. It was 6/3 is it the first number that should be higher and the second that should be lower for an ideal line?

[WWWombat]

For plain FTTC, the DSLAM and modem use a "target SNR margin" when negotiating the sync speed. They choose sync speeds such that, after synchronisation, the actual margin will be 6dB (*). Afterwards, the modem will display the actual measured SNRM as line conditions (such as noise) vary.

What you want, then, is for the SNRM to be 6dB after a sync, and remain at that forever.

You might not end up at 6dB, though, if either the maximum package speed is reached, or DLM has set you to a lower "banded" speed for stability reasons. In both cases, your actual margin will be above 6dB.

In practice, higher margins mean lower error rates, so are good - but only if you have the full package speed.

(*) - BT have been trialling the use of lower target SNRM values - of 5dB, 4dB and 3dB. They are now in the process of rolling this change out, so you can expect to see target (and actual) margins lower than 6dB.

[WWWombat]

It was 6/3 is it the first number that should be higher and the second that should be lower for an ideal line?

It looks like the first number is upstream, and the second number was downstream.

In fact, downstream was 3.4dB - which is a common result of the new target settings from BT: We call it 5dB, 4dB and 3dB, but the actual values we've seen in practice seem to be 5.4dB, 4.4dB and 3.4dB. No idea why.

Perhaps your line had been switched to the new setup, but DLM swapped back to the standard target as part of the engineer visit.

[alexxx]

Thank you - very helpful indeed

[alexxx]

engineer was a no show. got a text at 6pm saying one had been assigned yet they were meant to be there by 6. that was 2 days ago :/

[alexxx]

Ok so pulling my hair out a bit now.. 3rd engineer who came "oh you line can only support 43mb down..." well it can't as it was 60/18 rock solid for 2 months... for some reason he can't seem to get the noise to go back to 6.0db / 3.0db and its staying at 6.0db/6.0db

Nevermind it going to the 73mb down minimum promised.. It looks like I can't even get back to the 60mb down I had and stuck with 43mb..

They engineers are all really nice guys but they don't seem to be able to tell me much about anything.. all feels a little secretive or like they aren't they right guy for this particular problem.

Any advice on where to go next?!

[j0hn]

Nobody can force the line back to 3dB target SNRM.
DLM should automatically apply this in time if the line remains stable.

That may be all the line is able to achieve now. Almost every single FTTC user sees a drop in speed over time caused by crosstalk. Quite often bigger drops than what you have seen.

[alexxx]

The line was super stable at 60mb/18 though and only changed when the last engineer was fettling so I don't see how thats likely due to crosstalk as it's surely too much of a coincidence? Is there really no way to put it on a fresh port or whatever it'd be called and do a "this is a fresh connection" type setting to hopefully achieve the 60/18 again?

[kitfit1]

This might seem a silly question Alex, but what Modem and router are you using ? When was the last time you did a Firmware update on either ?