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Author Topic: Unusual SNR drop  (Read 1435 times)

banger

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Unusual SNR drop
« on: October 30, 2018, 11:31:26 PM »

Is it due to cold weather or something else. Seemed to go up then settle back down at 2.8db. All very strange.
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Tim
talktalkbusiness.net & freenetname
Asus RT-AC68U and ZyXEL VMG1312-B10A Bridge on 80 Meg TTB Fibre

https://www.thinkbroadband.com/speedtest/1502566996147131655

burakkucat

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Re: Unusual SNR drop
« Reply #1 on: October 30, 2018, 11:50:10 PM »

I suspect the "something else".  :)

I don't expect a weather related change to manifest itself with a clear straight-sided step in the observed circuit parameters.
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banger

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Re: Unusual SNR drop
« Reply #2 on: October 31, 2018, 12:17:34 AM »

Could it be a HRJ somewhere on my line? I shall monitor for a while as it has been a steady 3.3db for quite some time now.
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Tim
talktalkbusiness.net & freenetname
Asus RT-AC68U and ZyXEL VMG1312-B10A Bridge on 80 Meg TTB Fibre

https://www.thinkbroadband.com/speedtest/1502566996147131655

burakkucat

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Re: Unusual SNR drop
« Reply #3 on: October 31, 2018, 12:55:31 AM »

Could it be a HRJ somewhere on my line?

I would not expect to see a clean straight-sided step change as a result of a HR joint.

Quote
I shall monitor for a while as it has been a steady 3.3db for quite some time now.

That would be the sensible option. (If the service works, just make use of it and don't be too concerned over non-service-affecting observations.)
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j0hn

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Re: Unusual SNR drop
« Reply #4 on: October 31, 2018, 01:35:04 PM »

Looks very similar to the effects of a crosstalker.

The short, sharp increase in SNRM is a neighbours line resyncing, increasing your SNRM for a single sample as they aren't connected.

Usually your SNRM would return to normal at the next sample but it has dropped slightly.
Perhaps this other line has had their target SNRM reduced and is now making use of the D3 band that they weren't before their resync, lowering your SNRM slightly.

SNRM per band may show more detail.
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banger

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Re: Unusual SNR drop
« Reply #5 on: October 31, 2018, 08:43:31 PM »

Thanks John here's the SNR per tone.
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Tim
talktalkbusiness.net & freenetname
Asus RT-AC68U and ZyXEL VMG1312-B10A Bridge on 80 Meg TTB Fibre

https://www.thinkbroadband.com/speedtest/1502566996147131655

j0hn

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Re: Unusual SNR drop
« Reply #6 on: October 31, 2018, 08:52:22 PM »

Sorry it was the next tab along I was after, SNRM per Band.
If you scroll back in time to when the SNRM jumped up/down it should show what happened on each downstream band (D1, D2 & D3).
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banger

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Re: Unusual SNR drop
« Reply #7 on: October 31, 2018, 10:29:32 PM »

Sorry John cant find that tab maybe 6.5 doesn't have it or I havent enabled. Also thanks to Windows Update a reboot has occured in between the two times so my recording has effectively started again unless there is a history?

Edit: Found SNR per band and enabled it but unfortunately a reboot is in the way.
« Last Edit: October 31, 2018, 11:29:21 PM by banger »
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Tim
talktalkbusiness.net & freenetname
Asus RT-AC68U and ZyXEL VMG1312-B10A Bridge on 80 Meg TTB Fibre

https://www.thinkbroadband.com/speedtest/1502566996147131655

Weaver

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Re: Unusual SNR drop
« Reply #8 on: November 02, 2018, 06:59:35 AM »

I too am getting something like this regularly on one of my lines.
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