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Author Topic: Evening interference  (Read 798 times)

rhohne

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Evening interference
« on: May 04, 2019, 12:41:00 PM »

During the day interference is at a minimal, but come the evening it wipes out D2. The attached isn't the worst I've seen it but can be seen on a regular basis.

Anyone any ideas what could be causing it and how to get it removed
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PhilipD

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Re: Evening interference
« Reply #1 on: May 14, 2019, 08:51:44 AM »

Hi

All you can do is monitor the time to see exactly when the interference starts.  If it is exactly the same time each day then usually points to some machinery or equipment being turned on automatically.  It's easy to rule out things in your own property, but next to impossible to track something down locally, and even harder if you do find the source of interference to get anything done about it.

If the time varies somewhat, my guess would be this is someone turning on and off their VDSL modem, i.e. they turn it on in the evenings when they are home, and turn it off later when they go to bed to be "green" to save electricity, or they are the sort of person who worries about electrical fires and turns things off.  This means you are just seeing cross-talk come and go and a reason why BT prefer VDSL modems to remain on 24/7 as these sort of fluctuations can get reported as faults.

Regards

Phil

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4candles

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Re: Evening interference
« Reply #2 on: May 14, 2019, 12:12:29 PM »

Probably coincidental, but I was struck by the fact that the affected tones are in the range from 5900 to 6200kHz, which is the shortwave 49m broadcast band, - heavily used in Europe.
https://hfradio.org.uk/html/sw_radio.html
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Most things are somewhere else

johnson

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Re: Evening interference
« Reply #3 on: May 14, 2019, 04:42:06 PM »

Good spot 4candles.

At night the most reflective layer of the ionosphere changes height, causing RF sources to bounce much further. This means RF sources from all over the place carry much further at night and mess with our wet string DSL over copper.

Also the night time has street lights with noisy ballasts, houses full of people using switch mode PSUs and god forbid, plasma TVs.

If the time and duration are exactly predictable or clearly linked to a neighbour arriving home you might have a shot at finding the source. I did once with a direct neighbour and a junk chinese power supply with no output filter. But if you are talking about the general increase in noise during the evenings then unfortunately its just the nature of receiving your connection via this infrastructure.
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PhilipD

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Re: Evening interference
« Reply #4 on: May 15, 2019, 10:50:29 AM »

Hi

Yes night time can cause more interference, especially if the OP is served by overhead wire.  I'm all underground here and the SNR doesn't vary at all from daytime to night time, as the ground acts as a good screen.

However the effect of bouncing radio waves of the ionosphere is less than most people think on VDSL as what is received is very weak compared to the VDSL signal travelling physically across a wire for a few hundred metres.

I suspect the cause is pretty local, but finding it will be a challenge, and is just a consequence of the kludge that is xDSL.

Regards

Phil

 



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rhohne

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Re: Evening interference
« Reply #5 on: May 16, 2019, 09:20:51 PM »

Thanks for the responses

Wire is overhead to the end of the road and then disappears underground.

I've been monitoring the SNR totals in the D2 band and it showing considerable daytime/night time variations. QLN is fairly clean if daytime sync, however peaks are there if sync takes place overnight.

Edit: QLN is for a resync on 2019/05/13 @ 02:10:05
« Last Edit: May 16, 2019, 09:29:24 PM by rhohne »
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