The great morning glitch!! any idea's welcome

I am sitting on the end of over 4kms of wet string, mostly my service is now reasonable after some serious prodding my ISP however I am left with the great morning glitch!! this occours like clockwork Monday to Friday but not at weekends!! we have no streetlights, some overhead power, no industry in our village but quite a bit in the town (Watton) where the exchange is located.

Please see http://ge.tt/5ShciF62/v/0?c for the glitch in downlink snr ~3.5dB mysteriosly uplink is not affected, for tones before and after see http://ge.tt/6vZqiF62/v/0?c and http://ge.tt/3pF2jF62/v/0?c

Todays glitch is at http://ge.tt/4o9SlF62/v/0?c
I would apreciate any ideas or if anyone else has/is having a similar experience

Edited by deleted (Fri 05-Dec-14 10:46:50)

No mystery, radio interference will affect different frequencies in different ways, a bin plot of the SNR margin for each frequency bin may help to reveal more about the issue and the top video on http://www.thinkbroadband.com/videos.html shows how to use an AM radio to hunt down interference.

Thankyou for your reply I did provide before and after per tone snr plots, did you want bits/tone ?
Given the source is not in my house (nothing turned on/off) and all the wiring is twisted pair surely we are talking a LOT of rf power for this ?
Actually whatever it is has just turned off again, see http://ge.tt/1bkjtF62/v/0?c

I am foxed by the snr curve shape BUT i think i can think of a reason and that is the actual inteferance remains constant but over time the bitswapping partly works around it possibly by overloading other tones a bit as the error rate does go up during the inteferance.
Maybe if I can get an snr/tone shot immediatly after it starts i will be able to see the frequencies more clearly.

This has to be a mother of an RF source, but we have an old RAF base with comms towers on it and plenty of processing factories with chunky inverter drives in them!! Not much sun about so i dont think its a solar inverter and the big 5MW turbines are a good 5 miles in the wrong direction plus neither of these sources keep strictly business hours!!
Sounds like I am in for lots of fun here

From what I can see so far I am being hit at 146-168Khz, 444-460Khz, 526-539Khz & 680Khz. Nearest match so far is 160Khz plus 3rd and 4th harmonics with ~500Khz unknown. 160Khz hmmmm ?????

Edited by deleted (Fri 05-Dec-14 12:30:57)

HI,

I've experienced the exact same thing, heres an example noise margin graph [IMG]http://i62.tinypic.com/sxi0q0.jpg[/IMG]
http://tinypic.com/r/sxi0q0/8

It took a hell of a lot of tracking down , but I finally found the source of the drop in snr (and it turn connection drops and reduced speeds). The drops were caused by a (fairly distant) neighbour turning their broadband on!

Unusually they turned their broadband off overnight (because the power socket was also used for a lamp), hence why I could see the issue. It took a long time, and 3 engineer visits before I finally got an engineer who was able to understand the graphs and believe what i was telling him (his test equipment showed no line issues). He then comared my speed with others around and could tell it wasn't right, he swapped my pairs from the exchange and problem was solved. Went from 5.5mb to full 8mb (adsl max)and no snr drops anymore.

You can see on the graph i posted the effect this was having, That graph shows when i asked my neighbour to turn off their broadband for 15 mins for me (they did it at 15:00)

Hope that helps

Ohh thank you for the reply
Of course what better source close coupled over a long distance than another ADSL line in the same cable, after all I have over 4kms of oppertunity
Must be someone who turns on/off according to usage, funny they dont use it at the weekends so must be some sort of business premises, so I think I need to collect a daily schedule, spy on all my neighbours (normal activity in small villages) thank you again

Sorry missed the bin plots earlier

The major dips have all the hallmarks of radio transmissions, time to check with an AM radio if stations are present, if it is distant AM radio it will be worse at sunset and improve again after sunrise (AM radio can bounce off part of the atmosphere).

Also need to adopt a walk around the village with an AM radio to see if noise is obvious from a certain quarter. Past reports have seen fluorescent strip lights killing ADSL in a building, through to a dodgy PSU in a Sky box killing ADSL in a 100m radius.

It might be something as small as something is plugged into a switched mode charger and only happens at that time each week. Weekly laundry is a thought.