Noisy Neighbour ?

[#1]

Here's an odd thing; my neighbours went off on holiday yesterday at 7:40am - and  at 07:32 my SNRM leapt from a steady'ish 6.6db to 9.6db, without any resync/restart)  and is remaining in that vicinity in an equally steady fashion. In the past, at periods I now believe also coincided with my neighbours being away, I've had at least 2 similar experiences - but to prove the point I'll have to wait till they get back, then I'll see if they'll cooperate with a bit of testing.
Their telephone line comes from the same telegraph pole as mine, and travels above my garden  for some 45 yards or so; my line is about 25 yards pole-house, at 45 degrees (horizontal) to his line.
I'm wondering whether I normally get phone line to phone line interference between our lines, whether its adjacency line issues further away, or whether his router/filter arrangement is suspect. Equally, I suppose, there may be electrical interference.
Has anyone else encountered anything similar with noisy neighbours?

[#2]

Yes it is possible to get "crosstalk" between lines (even if it wasn't your immediate neighbour). Normal telephone lines are "balanced" and crosstalk is usually very low. When lines are sufficiently un-balanced (due to a fault) crosstalk and external interference pickup will be increased, in more extreme cases you may hear a "squawking" type of audio from another line if two affected parties are using the phone. A 3dB change however is quite significant and suggests the possibility of something else other than just their BB being on or off.
You should both carry out POTS auto line tests to see if that shows any faults, but also look at the possibility of other electrical interference from anything they normally have on all the time but have turned off whilst away (that should include any cordless phones).
HTH.

[#3]

I would concur with everything anotherone says, except ISTM to be highly unlikely to be a result of crosstalk between the lines, especially if it's causing a 3dB SNRM difference.
Assuming it's something your neighbour only ever switches off when away for a while, my 'favourites' would be Freeview/Sky (or other set top box), router, computer, cordless phone, and Homeplugs (ethernet via mains wiring).

[#4]

JFTR an approx. 0.5dB change in SNRM when a "neighbouring" BB is switched on/off is not uncommon.

[#5]

Every silver lining has a cloud !!
The unfortunate consequence of the apparent noise reduction bonus is this - at the next resync following the noise reduction, my sync rate jumped from its previous practically-stable-for-4-months value of around 1440 @ SNRM 8 (with medium/low error rates),  to over 1900 @ SNRM 9 (target SNRM was 9 for whole period), but regretably with a high error rate....eventually the BT kit then upped my target SNRM to 12 and my sync dropped to 1088 (with very low error rates).
Even more regretably, I then connected my router  to the engineers socket....and then back to the original when no change found....and at that point my router synced at 1088 at around 14, leading me to think that my target SNRM has possibly been raised to 15. I've just asked PN for a reset to 9 - I recall from a Forum posting that PN is (soon?) to be able to reset SNRM at 'the press of a button'.
Well, I've learned that my previous 1440 (and profile of 1250) seems to be the limit for my long line (68.5db attenuation), and once back to that I'll try to keep it at that level.

[#6]

Update:
When my neighbour returned from holiday and switched on his electrics, my SNRM dropped by almost 3db right away (this was at 5am) and stayed low. Eventually, a few days later,  I managed to have a talk with him and do 10 mins of testing before he went out. Simply powering off the power strip that supplies his router, cordless phone and FAX, and unplugging his microfilter restored my SNRM upwards by almost 3db (all that kit is within a metre of his phone wall socket). His power strip neon had been flickering oddly/irregularly, and his filter looked old, so I gave him a new power strip and filter....powered everything (except FAX - rarely used apparently) back up, and my SNRM dropped by only 0.5db. I reckon it was the power strip that was the issue, tho I haven't confirmed the effect of the FAX machine (as yet), or the close proximity of all his kit to each other.
I still reckon its very odd for this to affect my broadband so significantly - all this kit of his is approx 50m away from my socket/filter/router - can spikes/interference travel over the phone line to my setup?

[#7]

yep. thats why you see natrual dips and raises in snr over night.
if faulty street lights ect can effect your line its possable for things like faulty pc monitors ect to effect adsl signals in the area.
my sisters pc monitor started making a humming noise and taking its time to start up and i could see the effect of this on my snr

[#8]

Quote from: jack21

I still reckon its very odd for this to affect my broadband so significantly - all this kit of his is approx 50m away from my socket/filter/router - can spikes/interference travel over the phone line to my setup?

Well once your cable gets to the street and the junction box - it is with millimeters of his cable, in fact it will be in the same cable after the JB and if there is an imbalance on your lines they will most certainly interact.
This is why we need to ditch ADSL and get Fibre Optic links to the exchange.