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Author Topic: Daily DS SNRM Drops  (Read 2447 times)

g3uiss

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Re: Daily DS SNRM Drops
« Reply #15 on: September 17, 2019, 03:49:40 PM »

Given its most likely an external issue of a spurt of noise, would interleave or getting the SNRM increased to 9db be a possible solution, if so which is likely to produce the better result?
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Weaver

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Re: Daily DS SNRM Drops
« Reply #16 on: September 17, 2019, 05:10:26 PM »

Considering the SNRM variations which I was experiencing in each day, I increased my upstream SNRM target to 9dB. I was getting upstream SNRM sharp drops/rises of 4dB or so each day and that way it would make sure that my worst-case minimum daily SNRM would always be high enough after a drop so that the value would then be so low as to risk data corruption
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g3uiss

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Re: Daily DS SNRM Drops
« Reply #17 on: September 17, 2019, 05:17:20 PM »

Thanks @weaver. I will give that a try, in my case it drops to -1 if I added a headroom of 3db it should still stay in sync.
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g3uiss

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Re: Daily DS SNRM Drops
« Reply #18 on: September 18, 2019, 09:52:24 AM »

Interesting the last two mornings ( 10 minutes earlier) the modem didnít re sync, but I got a PPP drop on the router. It looks like a shorter but bigger CRC spike and SES also but there wasnít a SNRM drop. So I even more confused as what if anything to do. The PPP drop is only as long as it takes to re connect. Perhaps I should just hope the interference just goes away ?

On the VDSL. Circuit I see the massive CRC spike 1000 for and a 2db SNRM drop but stays in sync. The total ES daily is around 750 on DSL Stats.
Tony
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tubaman

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Re: Daily DS SNRM Drops
« Reply #19 on: September 18, 2019, 11:18:13 AM »

Do you have any industrial units or similar close to you as this sounds like the type of interference you'd get from a badly suppressed large electric motor or machine being started.  Another possibility is a poorly suppressed vehicle that is sending wide-band interference for a short period as it starts-up and drives off.
 :)
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vic0239

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Re: Daily DS SNRM Drops
« Reply #20 on: September 18, 2019, 03:02:52 PM »

I have a similar issue. Since January my line experiences a huge spike in errors twice daily at roughly a 12 hour interval causing a retrain. It is not exactly 12 hours, but usually some time just after 06.00 and 18.00 hours so I think it may be some human activity around these times not a timer event. OR investigated and gave the line a clean bill of health despite seeing the step change in their line history stats. Neither they nor my ISP were prepared to investigate further. I live in a small village with a few shops, hotels and a garage, but I suppose any one of these might have some equipment that could produce this issue.

My line syncs at 67Mbps, but I have capped it at 50Mbps which appears to reduce the effect on the line and stops the re-syncs. I am on the 3db profile, capping increases the SNRM to 8.8. Interestingly I have not noticed any reduction in performance at 50Mbps, probably not that surprising given our usage pattern.
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g3uiss

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Re: Daily DS SNRM Drops
« Reply #21 on: September 18, 2019, 05:14:09 PM »

Thanks. Sounds like @vic has the same. Iíve no industry around and nothing like a vehicle as itís to precise on the timing. I wasnít going to even try ISP or OR they wonít find any fault.

Mine is ADSL2 so I canít cap via the HG612 but Iím going to ask ISP to increase SNRM to 9 ( from 6). The line is secondary so the speed drop wonít be too significant. Iím just going to wait a few days and see if it goes away again as it has before. I guess being ADSL2 one retrain a day wonít cause any long term issues anyway, unless Iíve missed something?
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Weaver

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Re: Daily DS SNRM Drops
« Reply #22 on: September 20, 2019, 03:26:37 AM »

@vic0239 - thereís a lot of this kind of thing going around it seems  :)

I had this visible in the form of SNR spiking for several weeks but it was many times per day; also it was downstream-only.

In addition I have one line with variable upstream high-level/low-level SNRM on a 24 hour cycle with Ďhighí so many hours in the day, Ďlowí so many hours in the day. This is a square wave with duty cycle that is very very roughly 50%, well, not near 0% or 100% anyway. Also a second line shows a smaller less regular squarewave.
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vic0239

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Re: Daily DS SNRM Drops
« Reply #23 on: September 27, 2019, 03:42:39 PM »

Well this is interesting. Iím away from home at the moment and checking my stats (I know Iím sad, but it has been raining a lot) I note that there have been no DS errors since we left. Zero.

I switched a few things off before leaving, one of which was the central heating boiler. I had discounted this despite it being newly installed just before the problem started as it cycles many times during the day and my errors occur at just these two time frames.

However, Iíve been developing a theory that the culprit could be the thermostat on the hot water cylinder. My reasoning is that the new boiler is much more efficient and the temperature of the water is higher resulting in the thermostat cutting off whereby it may never have in the past and the hot water timer is on at these times.

Does this theory hold water (sorry)? Could such a device cause such a spike of errors? Iíll obviously experiment when I get home, but would be interested if this is plausible.
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g3uiss

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Re: Daily DS SNRM Drops
« Reply #24 on: September 27, 2019, 11:20:46 PM »

@vic. Iíve exhausted anything in my home that occurred at 0919 presisly everyday.  It must be external, and the hope of finding that zero. So itís a case of living with it Iím sure. The CRC spike is over 1000, so itís a big chunk of interference.

Frustrating to say the least. 
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burakkucat

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Re: Daily DS SNRM Drops
« Reply #25 on: September 27, 2019, 11:35:15 PM »

. . . Iíve been developing a theory that the culprit could be the thermostat on the hot water cylinder. My reasoning is that the new boiler is much more efficient and the temperature of the water is higher resulting in the thermostat cutting off whereby it may never have in the past and the hot water timer is on at these times.

Does this theory hold water (sorry)? Could such a device cause such a spike of errors? Iíll obviously experiment when I get home, but would be interested if this is plausible.

Yes, that is feasible. Any load switched on or off could be the cause of an RF spike and/or an EMI pulse via the mains wiring.

Some years ago NewtronStar went all round his home, fitting RC suppressors to all switches, etc, in an attempt to reduce (or eliminate) the errors on his VDSL2 service that he was seeing.
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tiffy

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Re: Daily DS SNRM Drops
« Reply #26 on: September 28, 2019, 12:22:31 PM »

As b*cat has said, any load switching device such as a heating/zone thermostat can generate noise either directly or via mains wiring, had an occurance on my daughters system where the oil fired boiler thermostat was generating a considerable amount of noise clearly visable on the router stat's and also causing a "stutter" on all the house terrestrial TV's running on an amplified distribution system from outside aerials.

In this case I believe the interference was transmitted through the mains certainly in the case of the house TV's, not so sure about the interaction with the modem/router.

Anyway, replacement of the boiler stat. completely cured the issue on TV's and modem/router.

Likely stating the obvious, but it's all down to a process of elimination, being able to identify/eliminate if possible any local events which correspond to the modem/router recorded disturbances as logged by DSLStats.

Initial quick checks can be carried out on the heating/zone stats. by adjusting their respective set points loading and unloading, however, this is not completely fool proof as set point adjustment can be quick and "clean" whereas normal temperature change which is usually a much slower action can produce contact "noise" when approaching the set point from either direction, the classic symptoms of a dodgy thermostat.

Then, as g3uiss has said, after all local sources of interference have been eliminated it's down to possible external sources which is a completely different ball game.
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vic0239

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Re: Daily DS SNRM Drops
« Reply #27 on: September 28, 2019, 02:25:48 PM »

Thanks to all for your replies. Iím home tomorrow and the hot water will be switched back on pronto. I will keep a watchful eye on the line stats in that first hour. If my theory is correct I should see a spike. It looks a fairly simple device to replace if it is the culprit.
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vic0239

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Re: Daily DS SNRM Drops
« Reply #28 on: September 29, 2019, 05:55:08 PM »

That's it!  :yay:
Sitting at the computer I can hear the pump running and was able to detect when the thermostat switched it off. Nice little blip at each occurrence. Unfortunately the cylinder thermostat is now obsolete, so I will need to source an equivalent replacement.

@g3uiss I was feeling your pain until I came up with this theory, attempting to find the source of such interference is futile when it's outside your premises.
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tiffy

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Re: Daily DS SNRM Drops
« Reply #29 on: September 29, 2019, 08:52:17 PM »

Now that you have identified the source of interference I would next try manually changing the tank stat set point up and down around the current temperature point so activating/de-activating your CH pump (assuming that's what the stat controls) and checking if you still get the modem/router blip.

Compare this with normal tank temperature changes instigated stat operation with respect to noise generation.

If the former does not produce interference but the latter does then I would believe that the stat is indeed "noisy" when approaching it's switching point from either or both directions and needs to be replaced.

If interference is produced by both permutations then I would consider first fitting some form of Capacitive or Res/Cap suppression across the contacts before considering replacement. 
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