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[JohnRYoung]

Well, now that I don't have to resynch every hour, I have been able to watch the line with routerstats. I make the following observations.....
The snrm drops precipitately at exactly the same two times each day, 7.50 and 21.40 ... I have the routerstat alarm set to reboot when this happens, but if I leave that off, the connection stays but is unuseable. During the day, the snrm is very stable, but at exactly 17:00 each day, it starts a gradual decline, eventually forcing another reboot between then and the repeatable one at 21.40. After reaching a trough at around midnight, it then gradually rises until the 7.50 interruption. This is all the same during weekdays and over the weekend. I think it is bearable, but I would be interested in any possible explanations for this systematic behaviour. I am pretty sure there is nothing in my house that changes at those times.

[guest]

Can I suggest that you see if the times remain the same when the clocks change this weekend? You would expect a gradual decline in SNR once it starts to get dark if you have an overhead line (MF radio propagates further) and there is generally more electrical noise in the evenings anyway - microwaves, TVs etc etc. Off the top of my head I can't think why it should be so regular though - hence the suggestion for this weekend

Edit - how close are your neighbours houses and do you know them well?
Edit2 - are you by any chance in an "Economy 7" area where electricity is discounted between 1am and 8am?

[kitz]

I'm in total agreement with what rizla is suggesting...

You had problems a couple of months back then all went quiet for a while, this could have co-incided with having had a poor/ wet June..  then iirc things were ok for a while again when the weather was warmer.  Now it seems to have started up again.

There could be the Economy 7 thing - it could be a heating switch..  how about Lighting?
Florescent lighting is something that also crops up on occasions as being a cause.
Also have you tried the AM radio trick to see if you can pin-point anything with that.

If I were you I'd also ask my neighbours a few questions to see if that brings anything to light (sorry for the pun ;/).  Explain that youre having a problem with your adsl and the indications from the trouble shooting so far is that it could be electrical interference from heating/lighting, mentioning the times to them.

[guest]

Just to add :

I reckon it is an inductive load as the timing isn't exactly to the hour/quarter hour. That indicates to me that its probably an electromechanical timer switching something on. Now you don't generally come across those very often these days so either something fairly inductive (and "chunky" in power terms) is switching on or we're dealing with something old. eg modern central heating systems will use a digital timer which switches a relay (contactor) remotely - usually wirelessly. Older systems will have an electromechanical timer. Inductive loads have a tendency to weld the contacts closed on most digital timers if they try to switch the load directly.

Hope some of that makes sense

[JohnRYoung]

OK, the times of the predictable interruptions are the same after the clock reset....that is to say they occur at the same time of day GMT as they did BST. So that would fit with it being someone's timer IF that timer is also updated. In fact this does seem most likely. The increased evening electrical noise also fits, and yes, I do have overhead telephone AND electricity! That just leaves one thing I don't understand. How is it that the noise spikes, assuming that is what they are, have the effect of a sudden drop in snrm which then remains low (from 0-4 dB) stably until the router is either rebooted or told by DMT to resynch. In other words, how does transient noise lead to stable effect on snrm? And why does it reproducibly return to normal snrm with a resynch? Looks like the noise causes an internal change in the router (or the exchange?) that does not revert when the noise ceases. That surprises me, but perhaps does not suprise others who know more? The evening noise is getting worse as the night get longer, and my profile is getting dropped again ... a sad winter may be on the horizon. 

[Astral]

>a sad winter may be on the horizon.<

Stick your head in the gas oven now, to avoid the rush!

I get noise that affects FM radio in short bursts every five minutes, or so. I'm convinced that it is caused by a sewage pump that trips when the storage chamber is full. Trouble is I can't prove it and it would cost me to get whoever it is that deals these things to investigate. Fortunately it doesn't seem to affect my ADSL.

[guest]

Got to pop out in 10 mins so just a quick reply :

It sounds to me that your router/modem isn't doing bitswapping correctly. There are implementations of bitswapping which aren't resilient to large impulse noise transients.

Can I just confirm that :

a) The router shows a reduced SNR and will keep that SNR until a resync?
b) The router will return to the "correct" SNR after a resync?
c) The router shows a fairly stable SNR between 2140 and 0750 (doesn't vary by more than 1db)?

I'll have a think about this while I'm out.

PS - do you know your neighbours well, and how close are their houses to yours?

[JohnRYoung]

a) The router shows a reduced SNR and will keep that SNR until a resync? 
     --- confirmed.

b) The router will return to the "correct" SNR after a resync?
     --- confirmed

c) The router shows a fairly stable SNR between 2140 and 0750 (doesn't vary by more than 1db)?
     --- not quite. It is very stable from 0750 to about 1600 (was 1700 before clocks back, so it's when
          it gets dark). Then it starts to drop gradually while also showing increased short-period fluctuation
          (about 1.5 dB up and down from drifting mean). The drift is <= 1 dB per hour and continues till
          about 2000-2200. I have routerstats set to reboot after 60 seconds at <8 dB (otherwise it becomes
          unuseable). This causes one or two reboots between 1700 and the 2140 even. After midnight, it
          gradually increases again until the 0750 event. Attached is a tif file with a "typical" 24hr routerstats
          graph, with approximate synch speeds underneath the snrm trace.

I'll have a think about this while I'm out.

PS - do you know your neighbours well, and how close are their houses to yours?
       --- well enough on a good day if I am feeling very tactful
       --- I am the very small middle of a 3-house terrace

[attachment deleted by admin]

[guest]

The graph is about what I'd expect now that the nights are getting longer.

I think you're going to have to go and have a word with your neighbours - mention the times (0750 and 2140) that it happens and see if there's any reaction. Mention that you're probably going to have to get BT out to locate the problem and they will be looking for someone to bill for the work so its in everyone's interests to sort it out prior to that.

If you can find a broadcast radio station (one of the BBC ones preferably) which has noticeable interference at the times mentioned then you can get something done about it. If not then whoever is causing the interference can just ignore BT/you/whoever. I suspect that given what you've said about having to reboot at <8dB you will find that there IS interference noticeable between 2140 and 0750 but the time of year will make it difficult as MF stations tend to fall apart after dark.

It strikes me that the timing is very odd indeed. I doubt it would be central heating as keeping it on either all night (2140-0750) or all day (0750-2140) isn't normal - even for someone as far north as you*. Best not to speculate what it is until you have a word with the neighbours.

*I'm assuming from the time you say it gets dark that you're in Scotland. I used to live way way up north (Western Isles) you see, so I remember 5-6 hours of daylight in winter

[JohnRYoung]

And finally .... since the last weekend, the repeatable timed inerruptions have stopped and I have had a stable connection since then. Central heating now on all day? Telepathic neighbours? No need to speculate any more, but maybe it will come back in the spiing. I will let you know. Until then, I think we can let this thread fade into obscurity, but only after I have again thanked all those who were kind enough to consider my problem. Thank you. 

[guest]

Glad its sorted - for now at least. If the problems do start up again I'd appreciate it if you could let us know as I have a theory about the cause of this. I'd need accurate timings & dates to be sure though

[kitz]

Im glad that it seems to have sorted and lets hope it stays that way [need a fingers crossed smiley]

Out of interest did you make any subtle enquiries with your neighbours?

>> I have a theory about the cause of this. I'd need accurate timings & dates to be sure though
>> If the problems do start up again

Yes indeed -please let us know John how it goes.

[JohnRYoung]

No communication with neighbours at all, unless they happened to read this forum ... if they were having the same problems 
However, although the abrupt repeatable interruptions have indeed gone away, I do still seem to get a terminal fall-off in snrm every evening starting about 3:30 pm which usually means I have to resynch to get an effective connection. Critical point seems to be about 8dB. Default on connection has reverted to 6dB - so I am dependent on DMT again. Don't know if any of that affects your theories