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Author Topic: More weird upstream SNRM variation - line #2  (Read 1296 times)

Weaver

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More weird upstream SNRM variation - line #2
« on: April 23, 2019, 03:46:34 AM »

I have noticed that my line #2 is also showing cyclic upstream SNRM variation, but a different waveform and a much smaller amplitude, only ~1dB high. Times are UTC, day is 2019-04-22



Line #2, despite the number, is the most recently installed one, installed last summer.

* What on earth is the short duration high state period - ~5:05pm - 7:25pm UTC - all about ?
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j0hn

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Re: More weird upstream SNRM variation - line #2
« Reply #1 on: April 23, 2019, 01:07:09 PM »

To my eyes the time period you mention is when the line is operating normally, at the 6dB target.
It's the 1dB drops between 11am - midnight that are when some form of interference is present.

What causes the 1dB drops in upstream is anyone's guess.
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Plusnet FTTC 80/20 -  ECI now Huawei cab
retx low @ 3dB target SNRM
Zyxel VMG1312-B10A bridged with 1508 MTU + Asus RT-AC68U running Asuswrt-Merlin

Weaver

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Re: More weird upstream SNRM variation - line #2
« Reply #2 on: April 23, 2019, 01:53:29 PM »

John - you make a very good point. I was thinking about the shape, itís not just a simple high/low waveform as for line 3. So maybe some device got turned off for that period. Will see what happens on other days.

Right now line 2 is Ďlowí @ upstream SNRM of 5 dB, and attenuation is 41.2 dB, power is 12.4 dBm. So the question is: is this a variation of noise or attenuation or output power? Iíll check when the graph goes high and compare.

With line 3 I think the conclusion was that it has to be a line fault [?] (was that agreed?) because it is attenuation that goes up and down, not noise, so the question is whether or not this is similar.
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burakkucat

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Re: More weird upstream SNRM variation - line #2
« Reply #3 on: April 23, 2019, 02:10:02 PM »

With line 3 I think the conclusion was that it has to be a line fault [?] (was that agreed?) because it is attenuation that goes up and down, not noise, so the question is whether or not this is similar.

Without looking back through the earlier posts, I believe that was my conclusion . . . the attenuation of the physical metallic pathway should not change in such a fashion.
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Weaver

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Re: More weird upstream SNRM variation - line #2
« Reply #4 on: April 24, 2019, 12:38:34 AM »

Even weirder waveform. This is not about a 24 hour period at all.

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DiggerOfHoles

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Re: More weird upstream SNRM variation - line #2
« Reply #5 on: May 06, 2019, 01:00:34 PM »

This is my cordless phone charging it's battery left. Right not. DS SNR.
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DiggerOfHoles

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Re: More weird upstream SNRM variation - line #2
« Reply #6 on: May 06, 2019, 01:08:36 PM »

What on earth is the short duration high state period - ~5:05pm - 7:25pm UTC - all about

Both patterns look like two shifts going to work and turning something on.

At 7km your line could pass a lot of noisy things on way to exchange.
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burakkucat

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Re: More weird upstream SNRM variation - line #2
« Reply #7 on: May 06, 2019, 06:00:10 PM »

At 7km your line could pass a lot of noisy things on way to exchange.

Except for the majority of that length it is just moorland, overlying granite bedrock.  ;)
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DiggerOfHoles

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Re: More weird upstream SNRM variation - line #2
« Reply #8 on: May 06, 2019, 06:04:15 PM »

Do the Belgians care?
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Weaver

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Re: More weird upstream SNRM variation - line #2
« Reply #9 on: September 10, 2019, 02:40:20 AM »

This has possibly returned - it is a bit soon to tell. But there is a step 1.6 dB high showing in the most recent graph:



See https://forum.kitz.co.uk/index.php/topic,23742.msg401882.html#msg401882
« Last Edit: September 10, 2019, 02:45:19 AM by Weaver »
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Weaver

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Re: More weird upstream SNRM variation - line #2
« Reply #10 on: September 11, 2019, 09:28:47 AM »

Line 2 - Tue 2019-09-10 to Wed 11. It seems that line 2 has now become the new line 3. Compared with how it was a month ago, now the waveform is regular, with a 24 hour period and 1.5dB height

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johnson

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Re: More weird upstream SNRM variation - line #2
« Reply #11 on: September 11, 2019, 10:30:49 AM »

I don't think I can offer any insight into the step changes in SNRM you have, other than saying I have experienced similar in my downstream and have no explanation. Lights switching on? Some sort of construction tools being used?

But I do enjoy seeing graphs from my firmware!  :D

V2 is coming, but I need everyone to be able to build it.
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Weaver

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Re: More weird upstream SNRM variation - line #2
« Reply #12 on: September 12, 2019, 08:57:43 AM »

Your firmware has been absolutely invaluable during the month of hell recently. It has shown exactly how bad and how widespread the problems have been.

As for cutting out some candidate explanations: it only applies to one line and not to others; itís upstream-only.

I need to look at the numerator and denominator of a ratio here, I think, and I have been lazy in not doing this earlier in this case. I need to look at the attenuation, power output and the noise level in the high and low parts of the square wave once more. If we assume for the moment that it is not the case that the output power of a transmitter is going up/down, then either the attenuation could be going up/down or the absolute noise level could be going up down. For the former, I would assume a change in resistance due to a Ďsemi-contactí make/break - I donít have the words I need here. For the latter, interference would seem more likely, but then we are stuck with explaining how it can only be one line.

Since line 2 seems to have taken on the upstream-waveform of line 3, while line 3ís upstream has been cured, I do wonder if someone possibly swapped E-sides when they fixed the recent month of hell. Would that be a possible candidate explanation?
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burakkucat

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Re: More weird upstream SNRM variation - line #2
« Reply #13 on: September 12, 2019, 05:24:16 PM »

Since line 2 seems to have taken on the upstream-waveform of line 3, while line 3ís upstream has been cured, I do wonder if someone possibly swapped E-sides when they fixed the recent month of hell. Would that be a possible candidate explanation?

We don't know if you now have four lines, divided into D-sides & E-sides, or just one line with a D-side & an E-side plus three EO lines. However we do have a strong hint that the fourth, latest, line you had installed has "taken" an E-side from one of the two cabinets (on the A87, at Harrapul (I hope I have spelt the name correctly)) for its deployment.

However pair swapping does seem to be indicated by your latest observations. 
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Weaver

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Re: More weird upstream SNRM variation - line #2
« Reply #14 on: September 12, 2019, 09:13:23 PM »

Thatís a good point. Line 2 is the latest, and has an E-side and indeed we donít know about the others, I shouldnít have made that mistake.

Yes, it could be taken as evidence for pair-swapping; line 2 became like the new line 3, but also more significantly, line 3 changed; its troublesome behaviour went away. So that suggests line 3 also has an E-side now, no?
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