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Author Topic: Daily DS SNRM Drops  (Read 846 times)

g3uiss

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Daily DS SNRM Drops
« on: October 01, 2018, 05:03:49 PM »

Strange problem arisen over last few weeks.

Most mornings at 0919 my DS SNRM fall to nearly zero on my ADSL line, there is a corresponding drop on my VDSL line but only to about 4db. Until today, the ADSL held sync, but today it fell so much it lost sync. I guess its a big bust of noise at a frequency in the ASDL range.

Strangely it doesn't happen every day but more than others, and more strangely it happens less days on the VDSL .

I have put some current stats at :-

www.west-lodge.com/adsl/index.htm - ADSL line

www.west-lodge.com/vdsl/index.htm VDSL line (Regretfully no snapshots uploaded recently )

There is nothing in the house with a timer or device that triggers at 0919. I suspect it must be external. It was happening when I was away and the house unoccupied and nothing running ?
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kitz

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Re: Daily DS SNRM Drops
« Reply #1 on: October 02, 2018, 10:30:07 AM »

I also have a noise burst which happens each morning that I've never been able to get to the bottom of and has been ongoing for a few years now.
 
It will cause my line to generate quite a few errors - as per the attached you can see throughout most of the day I only get 1 CRC, but the whatever it is will cause a sudden burst to around 2800-3000 which will last for about a minute. 

That spike is the reason why I have to monitor my line, because sometimes the errors will stick until I reboot my modem. If I don't then DLM will penalise me..  which is a PITA because by the time DLM catches up, the errors will have already stopped about 18hrs ago, but will take weeks to recover.  :/
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g3uiss

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Re: Daily DS SNRM Drops
« Reply #2 on: October 02, 2018, 02:24:15 PM »

Interesting. Very similar, I get about 3000 CRC on my ADSL2 when it happens at 0919, I did at first think it might be a new electric train. The cable from my UG DP goes over the railway bridge which you will know was recently electrified, but firstly there is nothing going under the bridge at 0919 and I guess it couldn't just be 1 train. (However Northern cancel more than run  ;D )

I'm going to have to live with it, like you unless it gets so bad that the line syncs every day. This morning the CRC was less and the SNRM dipped to just above 0 so it stayed in sync.

Do you get a similar SNRM drop to match and is the time constant ? Interesting if it is as its just a bit later than me ???

Have sent you a personal PM also

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kitz

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Re: Daily DS SNRM Drops
« Reply #3 on: October 02, 2018, 05:58:19 PM »

No corresponding dip in SNRm which is strange considering the amount of errors.  The only thing I can think of for that is there is a micro-second dip that dsl stats doesnt catch as it only records every 1 min.   In that instance CRCs would still show as they are based on accumulated errors rather than real time.

However that would not account for the fact that the CRC/ErrSec spike will usually last over 2 recordings.  I suppose there could be a couple of spikes, but you would have thought that because it happens daily and has been happening for years, that DSLstats would have caught it at least once.

>>> firstly there is nothing going under the bridge at 0919

Mine isn't always at exactly the same time.  It will usually be between 9.15 to 10:15 but can also happen any time between 8 - 11:30.  Today's was at 10:24 & 10:25.

I have seen similar on a few other lines just not as noticeable and I have in the past wondered if it is something at the DSLAM side.
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Weaver

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Re: Daily DS SNRM Drops
« Reply #4 on: October 06, 2018, 04:33:08 AM »

The question is, what happens at that time. Something getting switched off, or switched on? Heating turned off, or an oven turned on? (By neighbour) if so, something needs interference suppression.

Is there any chance that a mains filter might help? (No, because it is RF, going straight into the DSL line, not coming in by mains.)
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g3uiss

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Re: Daily DS SNRM Drops
« Reply #5 on: October 28, 2018, 03:18:48 PM »

Help !

The issue continued similar to as outlined by @Kitz. Mine was always at the same time, but apart from the spike in CRC and drop in SNRM I didn't until today, get any more re syncs.

Today, exactly 1 hr earlier I got the same, but this time a re sync. I assume whatever causes this is linked to a timer not changed back to GMT perhaps. However at 14:14 another busrt's of noise and a re sync. This time (I assume) the DLM banded me as the SNRM is now 12 (from 6), with consequent speed drop.

I'm really surprised the DLM would do that on a second re sync ?

Do I report to ISP, as they aren't going to see / believe my observation on CRC burst I doubt, but at some time I would need the SNRM resetting ?

(My VDSL line shows a similar bust of CRC but less and a drop of 2db in the SNRM, but to date no re syncs).

Stats at www.west-lodge.com/adsl/index.htm (no snapshots)

Suggestions more than welcome

Added (1626) I also note Iím missing a big batch of tones that were there before, something that has been debated before, but only odd tones,  now a great big gap ! Also QLN looks flat, could this be the balance of the noise burst at that caused the re sync ?

Tony
« Last Edit: October 28, 2018, 05:37:36 PM by g3uiss »
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boozy

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Re: Daily DS SNRM Drops
« Reply #6 on: October 28, 2018, 11:24:42 PM »

Oh dear you have my sympathy,

I've just had a similar problem fixed (although the engineer has no idea what fixed it).  The guess was substantial interference from another line/outside source which went away on the disconnection of a line in the area (I got the line as my second as there were no other pairs going to the DSLAM and the company had just closed).

If it's the same then your QLN will be noisier on the resync, but if you give it a few minutes and force as resync you will go back to your original speed and QLN - or will do until the resyncs cause the DLM to intervene.  So you may have to turn off your modem for 30 minutes to be safe.  The only certain thing for me was that rain caused the noise for my problem, your problematic source seems to be on a timer.  I think of it as crosstalk++ (or a real PITA).

The bad bit is that if you get an engineer then nothing will show up, as your pair is fine...  Ask your neighbours if they are suffering the same, as you may need numbers to get someone to do something about it.  At least you've got a time when it happens, but I suspect the duration will be too short to be useful.
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g3uiss

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Re: Daily DS SNRM Drops
« Reply #7 on: October 29, 2018, 08:30:34 AM »

Thanks. I think your right. I forced a re sync and the speed and SNR returned to normal, so did the bit loading and QLN.
I guess when the re sync happened yesterday it synced while the bust of noise was on.

Thanks

Tony
« Last Edit: October 29, 2018, 08:33:58 AM by g3uiss »
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