I wish I could suggest something else for you NS. Its the induction of some sort of noise that is causing the SNRm to fluctuate and until that noise can be completely eliminated then there's nothing else that could stabilise the SNRm. As far as the mechanics of DSL goes, then anything up to 3dB is classed as acceptable and normal variance. The longer the line then the more anticipated variance, so you'd less likely expect 3dB variance on a short line, but it would be normal on a long line.
Your variance over the course of the day looks pretty damn smooth and to me it looks like just general background type noise. I certainly wouldn't say its REIN/SHINE/PEIN and its now just the typical day swing you'd likely expect to see from
general atmospheric RFI. In fact I'd say your SNRm looks quite nice for the line length. The QLN tells a bit of a story - I dont like the spikes in the last band... but that in itself
could be typical of background noise picked up on long lines. It would at some point be interesting to see if a QLN in the morning is better than a QLN taken in the evening. Usual caution given re performing resyncs. Dont be in a rush to do it as Im not expecting to be around much over the next couple of days.
Your E/S looks quite acceptable now. I have a very strong suspicion that a lot of your damage was done during the early days before monitoring commenced. I suspect that you may have been doubled by the ILQ many times over and therefore you may have to wait longer for the DLM to relent. I dont know how much swing the DLM allows for SNRm before it repents, but I'd consider 1.5dB to be reasonable for any line. Id expect the DLM to only be looking at variance of say more than 3 or 4dB. If I had to take a guess and take a stab at a figure then I'd say DLM would look at less than 3.5dB as being ok. This is based purely on the fact that all DSL theory says 3dB is acceptable.
I so very much wish that the ISPs could request a DLM reset for fttc.. as Im sure your line would now perform quite happily.
Im also unsure about the effects of capping sync.. because if you are going to do it, you'd need to do so and keep it like that for a long time until the line recovers. If the ILQ system is monitoring your line in preparation for a reduction then any artificial capping that causes changes say from 6dB to 10dB and back again could do more harm than good. The DLM will see an SNRm change of 4dB and isnt likely to like it. The DLM will be far happier with a line doing a daily swing between 6dB and 8dB each day. It wont be happy to see a change of 10dB down to 6dB as it will just see a downward loss of 4dB and could class that as unstable.
I really do need to dig further into the ILQ aspect for DLM recovery because thats where Im up to, but Im sorry I honestly dont expect to be able to do that for a while. People are going to have to cut me some slack over the coming weeks as things are only likely to get worse. :/
