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Standard User lissie
(newbie) Tue 27-Sep-16 16:50:49
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Regular 3-hour periods of interference on DSL


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For a few weeks, I've been having intermittent issues with my ADSL connection. For periods of several hours at a time, normally during the evening and again during the small hours, I'm getting ADSL sync issues, very heavy packet loss and repeated disconnection. It's obviously some kind of local interference issue rather than a problem at my ISP's end but I can't figure it out.

I'm with Uno, and this is their ping graph for the past 24 hours:

http://i.imgur.com/ddjNa94.jpg

The random ping spikes are normal during use of the connection - the mystery is the long periods of heavy packet loss in red at the top of the screen. It goes on for a few hours at a time before abruptly stopping - this is a regular pattern observed over the past few weeks. There's no set pattern as to the time - it could be the middle of the day, the small hours of the morning or any point during the day or night but it always lasts for pretty much exactly three hours.

I just can't figure out what might be causing the issues. It's unlikely to be anything being physically switched on and off (eg. by the neighbours) because of the regularity of the duration and the fact that one of the problem periods is often in the small hours of the morning. I suspected the LED street light outside, but if that was the case then the issue would persist all evening/night, which it doesn't.

Has anyone out there ever seen anything like this before on their ADSL line, and if so, what was the culprit? I'd like to try and get this sorted out one way or another. (This is a standard ADSL2+ line, not FTTC.) Thank you in advance!
Administrator MrSaffron
(staff) Tue 27-Sep-16 18:20:57
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Re: Regular 3-hour periods of interference on DSL


[re: lissie] [link to this post]
 
Have you switched off all the power circuits in the house apart from one where the only thing connected is the ADSL2+ modem and hopefully a laptop running on battery to test the connection.

Of course if its for such a long period of time powering down a house is difficult, so maybe try and catch it the next time you get the bad block of issues.

Also have you confirmed whether the SNR margin and error counters in the ADSL2+ modem are affected? If they are rock solid and good even when connection is bad, then it may be nothing to do with the broadband at all. It might be a device doing a backup at random times, that just so happens to take three hours and is saturating upload as one idea.

The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User lissie
(newbie) Fri 21-Oct-16 11:55:08
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Re: Regular 3-hour periods of interference on DSL


[re: MrSaffron] [link to this post]
 
Sorry to bump this back up after such a long period, but this is still ongoing after quite some time. Uno's wholesale provider (TTB) can't find a fault on the line and I'd like to avoid an engineer charge if it's at all possible that it might still be my equipment.

My modem provides a helpful SNR graph and there's a definite difference in the graphs during good and bad periods:

Stable connection: http://imgur.com/a/ZEzfZ
Poor/no connection: http://imgur.com/a/NsZQT

There is a definite degradation in the SNR around the 64-100kHz mark during periods of high packet loss and loss of ADSL sync.

I've tried: turning off all the power sockets in the house except for the one to the router; using the test socket; putting ferrite chokes on the cables to the phone and router; changing the filter; changing the phone and DSL cables; trying a friend's borrowed modem; tuning a radio to 612 kHz and listening around (it's a non-stop buzzing noise during both the good and bad periods, including when I've had all power sockets in my own house turned off).

The setup is a very simple one, with no extensions or complicated wiring. It's just a BT master socket with a single ADSL filter plugged into it and a single phone and modem/router. Using the test socket causes no improvement.

The three-hour thing seems to have turned into a nearly-all-the-time thing. I rarely have a period of more than an hour with a stable connection now. There's also a loud crackling sound on the phone line during voice calls - however, when I mention it to the person at the other end, they can hear me clearly. It seems to be just on the incoming side.

If anyone can shed any light on what might be causing this before I get a potentially expensive Openreach visit, please do!

Edited by lissie (Fri 21-Oct-16 11:57:14)


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Standard User AdrianPH
(member) Fri 21-Oct-16 12:06:20
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Re: Regular 3-hour periods of interference on DSL


[re: lissie] [link to this post]
 
Plug a corded phone into the test socket ( inside the master socket).

Can you still hear the noise? If the noise is still present you need an engineer visit for a voice fault.
Administrator MrSaffron
(staff) Fri 21-Oct-16 13:02:17
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Re: Regular 3-hour periods of interference on DSL


[re: AdrianPH] [link to this post]
 
And just the corded phone i.e. no modems or microfilters

The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Administrator MrSaffron
(staff) Fri 21-Oct-16 13:07:42
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Re: Regular 3-hour periods of interference on DSL


[re: lissie] [link to this post]
 
If this was a cable fault I'd normally expect to see a much bigger effect on the higher frequency tones

The way the interference has a 10dB impact up to 600Khz and seems to then vanish for higher frequencies almost points at something locally creating wide-band low frequency interference.

The radio may be better tuned to a lower frequency in your case, i.e. an area around 300kHz where no radio stations are, the noise should vary as you move around, e.g. placing radio on top of ADSL modem should demonstrate the sort of difference you are looking for.

Have replaced all the microfilters? Just to ensure its not one of them failing and occasionally allowing voice to interfere with the broadband signal?

The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User Mendip
(newbie) Fri 21-Oct-16 15:21:35
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Re: Regular 3-hour periods of interference on DSL


[re: MrSaffron] [link to this post]
 
This thread reminds me of a problem I had several years ago at a different property.....

Very similar problems to the OP, similar effects on tones and SNR, and similar timing theme.
I followed all the usual diagnostic routes (line tests, lighting, heating, phones etc.) for tracking the cause over several weeks, and tried all of the OP’s tests and action including ferrite chokes etc. – nothing. The ISP was helpful but there was nothing wrong with the line (they were correct), even though they could see the effect on the SNR over time. But as Mr Saffron suggests, the only effective and easily accessible way to identify local radio interference is with a radio.

So I followed that route, and yes I could pick up a very weak signal at exactly the same time as the interference around 310kHz and 419kHz. I spent hours tracking around the property looking for the source – nothing. I even resorted to shutting down the entire Electrical supply and every device – the interference persisted (on the handheld radio). So it was nothing internally. The next few weeks were a bit mad, occasionally wandering around with the radio near other properties, suspecting neighbours etc. but nothing…..

I was about to give up and thought I would go for a walk down the fields, radio in pocket, and to my surprise the noise of interference became greater. It peaked right outside a sewerage pumping station, some 1000 meters from my property. Bizarre. shocked

Later I looked at the history, time v SNR drops and worked out roughly when the interference was being generated and again visited the area outside the pumping station, but before the interference had started and sat down with a radio and a book. I heard the pumps start, and bingo there was the exact noise!

OK, this could be all a coincidence, so I returned another day and even took my laptop, a 3G dongle and a VPN connection back to the router, and watched again. Sure enough exactly at the time the pumps started, the SNR halved!

OK, so I have a potential source, but how to convince the water company? Actually this was quite easy. After explaining that their equipment ‘could’ be interfering with my equipment, they sent a very helpful and knowledgeable Engineer to my property. I showed him all the research and evidence I had. Fortunately, he was a ‘proper’ Engineer and understood exactly what I was stating. He then suggested we take my Laptop live and visit the station with him. He went straight to the Switch Gear cabinets inside and was actually quite surprised / horrified by what he saw – the installation had been done by a sub-contractor and they had not Earthed any of the cabinets – in effect the whole Switch Gear room was acting as antenna.

The Engineer could only apologise, and set about an immediate on-site repair plan – within a week the problem was solved. They even sent me a thank you letter after the event – a lot of companies in many industries could learn from this example.

So what can we take-away from this?

The source of the interference may not be local to you, or indeed even near to you, if your cables pass by a source of interference on route to you.
• The interference was affecting other connections for sure, but no-one had done the leg-work to find the source. However, it might be useful to check with neighbours that are ‘tech-savvy’ enough to understand what you are talking about.
• It was surprising how helpful the local sewerage company was when approached directly. Sure there are laws against interference, but most companies these days operate a ‘denial approach’ rather than a helpful approach. The approach shown in this case may have, in due course, saved an Engineers life – remember the entire Switch Gear cabinet was not Earthed!!!

So as Mr Saffron says – a portable radio is a really useful tool in this situation and I hope you find the source of the interference. My connection speeds trebled after the source of the interference was removed.

Oh and the irony of the situation? The sewerage company had an ADSL connection to the plant to monitor its operation, and could not understand why it regularly dropped out – it miraculously recovered after rectification work and never dropped out again! smile

Hope this post is of some help and if I can help further please do not hesitate to ask. This forum is a brilliant source of information and help!
Standard User lissie
(newbie) Fri 21-Oct-16 15:21:59
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Re: Regular 3-hour periods of interference on DSL


[re: AdrianPH] [link to this post]
 
In reply to a post by AdrianPH:
Plug a corded phone into the test socket ( inside the master socket).

Can you still hear the noise? If the noise is still present you need an engineer visit for a voice fault.


Yes - a corded phone plugged straight into the test socket with no microfilter or other devices (ie. modem) plugged in still gives the crackling sound. There is also a very fast, repetitive tick-tick-tick sound in the background during periods when the connection is bad.

I'm not hearing anything on or around 300kHz with the portable radio within or in the vicinity of the house.

Any ideas? Thanks so far for your help!

Edited by lissie (Fri 21-Oct-16 15:30:11)

ISP Representative jongreen84
(isp) Fri 21-Oct-16 15:40:17
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Re: Regular 3-hour periods of interference on DSL


[re: lissie] [link to this post]
 
In reply to a post by lissie:
Yes - a corded phone plugged straight into the test socket with no microfilter or other devices (ie. modem) plugged in still gives the crackling sound. There is also a very fast, repetitive tick-tick-tick sound in the background during periods when the connection is bad.


I had this on my line once, and it turned out to be the AC balance was too low on my line. It wasn't so much the presence of interference, but my lines lack of immunity to interference. I believe it was caused by a jumper cable in my PCP (which is old), which had become untwisted over time.

I could also hear the common 50Hz mains hum on my line when the service was poor. Rejumpering in the cab, which increased the AC balance fixed it for me.

The above may or may not be relevant. I think it was a broadband engineer that resolved my fault, rather than a voice engineer, despite being able to recreate the issue with a corded phone in the test socket.

Thanks,

Jon
The above post has been made by an ISP REPRESENTATIVE (although not necessarily the ISP being discussed in the post).
Standard User AdrianPH
(member) Fri 21-Oct-16 15:40:49
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Re: Regular 3-hour periods of interference on DSL


[re: lissie] [link to this post]
 
So the problem is outside of your domain, you need to speak to Uno again and tell them.

OpenReach should look at the line for you.

It could be something like a pump or some other equipment running at intervals.

I remember a case several years back where 30 + houses had the same sort of issue, that turned out to be one of the residents who worked away from home 5 days a week, on returning on a Friday they switched on their stair lift and that swamped the area with noise. The lifts charging system was at fault.
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