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Erratic U/S SNRM and resulting DLM interventions

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jab1
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Erratic U/S SNRM and resulting DLM interventions

The problem described in my last thread on this subject (https://community.plus.net/t5/ADSL-Broadband/High-downstream-SNR/td-p/1590648 ) has returned with a vengance - starting on Saturday and continuing all the way through yesterday - RSL graphs which illustrate this better than I can describe below.

Despite the fact that, as referenced in the linked thread, @Gandalf had set a custom minimum downstream SNR of 6dB, DLM seems to be determined to set it at 3dB (too low for my length of line), at to set the connection speed at anything from 11 to 13 (too high for the length of line).

Any chance this could be investigated/resolved?

For information, the BT engineer I had out in an attempt to resolve the previous problem installed me anew (5C) box and told me (as I already knew) that a reasonable speed/SNR should be 8.5 at 6dB - anything else would be unstable, as the graphs illustrate.The only physical thing not replaced/altered in my set-up is the router, nut I suspect the problem is in the BT infrastructure - unless anyone can convince me otherwise?

 

NoiseMargin-2019Feb02-1124.jpgNoiseMargin-2019Feb02-1424.jpgNoiseMargin-2019Feb02-1724.jpgNoiseMargin-2019Feb02-2024.jpgNoiseMargin-2019Feb02-2145.jpgNoiseMargin-2019Feb03-1050.jpgNoiseMargin-2019Feb03-1350.jpgNoiseMargin-2019Feb03-1650.jpgNoiseMargin-2019Feb03-1950.jpg

 Edit to add - just before I posted this message, I had a phone call of about 40 minutes duration, during which I could hear a faint noise, which produced the kind of effect seen at the beginning of the last graph above, During that call, I also had a re-sync - to 11.8Mb/s, but with a much more respectable D/S SNR of 6.5dB.

Have carried out a QLT - no discernible noise.

John
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Re: Erratic U/S SNRM and resulting DLM interventions

Hi @jab1,

 

Testing the connection is still showing a 6dB target for both the upstream and downstream SNR targets, so it looks like the SNR Target is still pinned there.

 

Although there do appear to be a few drops which seem to match up with the times that the actual SNR has been dropping. As such it may be worth raising a fault report over at http://faults.plus.net if you've already been through standard troubleshooting.

 

I've discussed this with @MatthewWheeler, who thinks this could potentially be an intermittent noise fault of some sort.

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 Harry Beesley
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jab1
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Re: Erratic U/S SNRM and resulting DLM interventions

@HarryB Thanks for picking this up. Sorry got to go out in about 5 minutes for possibly the rest of today, but I will respond properly as soon as possible.

John
jab1
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Re: Erratic U/S SNRM and resulting DLM interventions


@HarryB wrote:

Hi @jab1,

 

Testing the connection is still showing a 6dB target for both the upstream and downstream SNR targets, so it looks like the SNR Target is still pinned there.

 

Although there do appear to be a few drops which seem to match up with the times that the actual SNR has been dropping. As such it may be worth raising a fault report over at http://faults.plus.net if you've already been through standard troubleshooting.

 

I've discussed this with @MatthewWheeler, who thinks this could potentially be an intermittent noise fault of some sort.


@HarryB All the tests requested have been carried out, the only extra one I haven't done is to use the test socket as I don't really want to disturb my connection whilst it appears to be stable.

I have just run a further QLT, which was perfectly clear (using my corded handset, not the DECT phone), and this disturbed both my U/S and D/S margins, but  not not enough to break my connection.

I will post my RSL graphs early tomorrow, in case they help.

John
Plusnet Help Team
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Re: Erratic U/S SNRM and resulting DLM interventions

No worries, let us know when you've raised the fault and we'll be happy to progress this and arrange an engineer.

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 Anoush Mortazavi
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jab1
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Re: Erratic U/S SNRM and resulting DLM interventions

My nice 6dB noise margin/11mB/s speed didn't lat that long - overnight it reverted to 14.4/7.8 RSL graphs from yesterday below:

NoiseMargin-2019Feb03-2142.jpgNoiseMargin-2019Feb04-1051.jpgNoiseMargin-2019Feb04-1351.jpgNoiseMargin-2019Feb04-1651.jpgNoiseMargin-2019Feb04-1950.jpgNoiseMargin-2019Feb04-2150.jpgNoiseMargin-2019Feb04-2150.jpg

I will raise the fault report later, but I'm still a little concerned that the engineer will come, declare 'NFF', and I get hit with a £65.00 charge.

John
jab1
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Re: Erratic U/S SNRM and resulting DLM interventions

As an aside, @HarryB, @Gandalf I have a second PN supplied router (still the TG model) - is there any mileage in substituting that one, or, as I suspect, is the problem outside my premises, and that would just be faffing about for the sake of it?

EDITED TO ADD: An incoming call at 0959 upset the line - again - noise margin down to 6.3dB and an increase in sync speed to 12.033Mb/s. What is going on?

John
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Re: Erratic U/S SNRM and resulting DLM interventions

As an aside, @HarryB, @Gandalf I have a second PN supplied router (still the TG model) - is there any mileage in substituting that one, or, as I suspect, is the problem outside my premises, and that would just be faffing about for the sake of it?

It may be worth trying that just for completeness to try and rule out the router, although I do suspect that it may not resolve the issue.

Although I suspect Matt may be correct with the advice he gave me yesterday, that it's potentially an intermittent noise fault on the line, which could be tricky to pin down.

 

Do all incoming calls cause this? As a trigger that you can replicate if/when an engineer visits could be useful.

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 Harry Beesley
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jab1
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Re: Erratic U/S SNRM and resulting DLM interventions

RE:The router - OK, as things are stable (at the moment), I'll put that idea on the back burner.

RE: Incoming calls - they have not previously done this, only in the last couple of days, literally.Unfortunately (or not) I get very few incoming calls on the landline as most of my contacts use mobiles, but I will keep an eye on it for a couple of days, maybe get someone to call the landline later, just to check.

John
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Re: Erratic U/S SNRM and resulting DLM interventions

Thanks @jab1, let us know how you get on with that.

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 Harry Beesley
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snadge
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Re: Erratic U/S SNRM and resulting DLM interventions

I had this issue (well, very similar), this started once I installed the NTE5C + Mk4 SSFP (Filtered Faceplate) - there are lots of bad reviews about this new NTE5C from Pressac, I thought I would find out for myself so I bought one and installed it, low and behold my sync dropped 2MB, Noise Margin on the Upstream was behaving oddly and a tenfold increase in CRC and HEC error counts (both up and down) - I reverted back to my NTE5A + Mk2 SSFP which resolved the problem.

The NTE5C is poorly built, it no longer has the regular Printed Circuit Board but some type of aluminium/metal plate, the Mk4 Filtered Faceplate is fairly well built but only works on a 5C type Master Socket


This is probably why they are very cheap on eBay, you can get an NTE5C with a Mk4 SSFP for as little as £5, yet the Mk1, Mk2 and Mk3 SSFPs alone sell for as much as £20

Just for reference, the differences between the Mk1-3 SSFPs are below:-

Mk1 SSFP - Fits NTE5A 
mk1.jpg

Mk2 SSFP - Fits NTE5A, has a Common Mode RF Filter in
mk2.jpg

Mk3 SSFP - Fits NTE5A, has a newer smaller Common Mode RF Filter in
mk3.jpg

jab1
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Re: Erratic U/S SNRM and resulting DLM interventions

@snadge Thanks for your reply, comments noted - BUT this problem has been going on for 12 months+, and changing from my old box (4 or 5 y.o. when replaced) has alleviated some, but not all of my issues.

As @HarryB has stated above, this is more than likely a noise issue, but as it is intermittent and (I suspect) downstream of my equipment, it is going to be a right pain to resolve.

John
jab1
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Re: Erratic U/S SNRM and resulting DLM interventions


@HarryB wrote:

Thanks @jab1, let us know how you get on with that.


Harry - just had a 5 minute call on the landline. It didn't break my connection, but did disturb my SNR plot - d/s rate fell from 9dB to 7dB and 'wobbled' a bit around that lower level, similarly, the u/s figure which had been steady at 6.3dB fell to 6.1 and was erratic around the lower level.

I'm not at home tomorrow (Wednesday), but will leave the laptop running and let it monitor the rate.

Further question while it's still in my mind - when I report the problem, do I report it as a phone or BB problem, as DLM intervened at some point after 2030 last night and raised the SNR to 14.5 and dropped the speed to around 7.8 - when nothing was in use?

John
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Re: Erratic U/S SNRM and resulting DLM interventions

Thanks for the update John.

I'd report it as a broadband fault as SFI engineers are generally trained to deal with both phone and broadband issues.

Let us know how your monitoring goes.

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 Anoush Mortazavi
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jab1
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Re: Erratic U/S SNRM and resulting DLM interventions

@Gandalf Cheers, Anoush - wait for the moans on Thursday.Wink

John