This is what I call Noise Impact!

Recently had Sky ADSL2+ BB installed (still in the training phase). Initially it synched up at ~10Mbps downstream with ~6dB SNR, and ran thereabouts for a couple of days fairly stabley.

I then started get swathes of disconnections (loss of synch) between around 9am and 5pm - each resynch would see the line come up with the same 6dB SNR but with ~1Mbps less line speed. Over 10 - 15 minutes the SNR would drop to zero, then resynch again.... and again.. each time resynching at lower and lower speeds. After 5pm the router would resynch back up to ~10Mbps / 6dB and be fine until the following morning.

Yesterday however, that final resynch did not occur and I ended up at ~1Mbps / 31dB. So I thought I would leave it like that and see if it could hold on through the next day without a loss of synch. Fired up RouterStats Lite to monitor things... the image linked below is the result (use the magnify glass tool button to see the full size image)...

http://i1066.photobucket.com/albums/u402/premmy9912/...

Something is obliterating the downstream frequencies with interference. Time to break out the portable radio - something that noisy should be pretty easy to pickup I reckon

Wish me luck!

Edited by deleted (Thu 05-Feb-15 00:40:04)

You don't have a Sky box plugged into the line with no filter, (or possibly a faulty one), do you? Given the time of day and the interference-free time it isn't likely, but worth just checking. Or a kitchen TV that was on at that time?

Where is the router in relation to anything else electrical?

No Sky box. Just the Sky router > new filter > new master socket - nothing else attached to the line at all.

No TVs in use in the premises.

Router is the only powered device in the room that it is in. Only other things powered during the time of that chart was my laptop (permanently on), microwave (intermittent use), fridge/freezer which kicks in and out all day and night, electric shower for 10 mins or so. Whatever is causing that >30dB hit is external to my premises.

I suspect the two square lumps either side of the massive dip are a neighbour's heating going off for the night, then coming on again in the morning. That looks to be a ~2dB hit.

I worked in DSL support for years so I know this will be a fun one to get resolved

looks like central heating problem..slow deterioration from sudden start @0700 ish and gradual improvement afternoon when the house is warmed up by the sun and sudden switch off at 2200.??

Unlikely. Yes, pump and boiler starting up could cause it and a continuous pump running would keep the noise level high. And whilst warming up during the day is a possibility the heating would kick in occasionally and certainly after dark I would expect the heating to be on up until maybe 22:00 or a little later. There is nothing after 13:30 or so.

An easy way to check would be to turn off CH at a fixed time say 10:00 and ask the neighbours to do likewise at 11:00 and 12:00

Maybe a neighbour has a solar PV installation facing South East and the inverter kicks in at sunrise and finally stops in te early afternoon?

I would be also walking the cable route back to t the cabinet and potentially exchange and looking for businesses that are close by.

Updated charts for both noise and speed...

SNR:
http://i1066.photobucket.com/albums/u402/premmy9912/...

Speed:
http://i1066.photobucket.com/albums/u402/premmy9912/...

Ended up on ~7Mbps / ~8dB once the interference subsided today at around midday. Which means I'm in for a boat load of reconnections tommorow when it kicks in again.

Interesting the times are not consistent each day, which would seem to indicate something being manually switched on / off. Will be keeping an eye on it over the weekend - may give a clue as to whether it is residential / commercial. If I have the line routing correct (all underground so hard to be sure) - then the line passes in close proximity to a parade of shops and a small trading / light industrial estate plus some residential on its way to the exchange.

I suspect there is more than one source of interference. Check out the squared off bump of ~2.5db each night at the top of each curve...
http://i1066.photobucket.com/albums/u402/premmy9912/...

That would be consistent with central heating going off for the night.

You can easily check that. After it has gone off, leave for 30 minutes, turn on, run for 30 minutes and then turn off.

You have tried the obvious, and tried a different router ?

Indeed so ~if~ I knew whose heating it was. Certainly not mine

Not as yet. Still in the Sky training / assessment period so I'm disinclined to meddle with it. Plus I've yet to go through the faff of extracting username / password from the Sky router.

Neighbours above or below? A semi- with your router against wall? Lining in a block of flats and telephone cables coming up a service duct? Line fixed to neighbouring property? Underground feed that passes under teh neighbours drive/garage/extension?

There are lots of possibilities, you can have a great time finding the source.

Have you just moved there, or have you been there a while and your previous broadband was fine?

Did you reboot at ~12:25:30? That is a disconnect/reconnect.

Edited by RobertoS (Fri 06-Feb-15 00:19:59)

This is a "new" line. Well, not new exactly, there was a line into the place with an LJ/2A that had been inactive for a number of years. Signed up with Sky as they were offering free "new" lines installation plus topcashback and M&S voucher with 12 month contract.

No, I did not reboot anything at 12:25:30 . The Sky router did reboot ~11:57 spontaneously (I have it set to send syslog messages to my log box). I'm guessing that's part of Sky's training period, having experienced a blast of noise, send a TR-69 instruction to reboot. Really I'd rather they just upped the target SNRM to stupid high levels or clamped the line to 512Kbps in this instance, so I can sensibly plot the noise hits.

Flats. Neighbours above and to the left and right and diagonally so!

All lines for my block arrive in a shared underground feed. Underground all the way to the exchange.

There's also shops, residential and a trading estate on the line's route to the exchange - the noise introduction could be anywhere.

Hence why I am not rushing to action, I know this will be a slow fix having worked on the other side of the fence so to speak. I'm in observation phase

You obviously realise the size of your task.

Monitor it for a few days to look for patterns - such as exact switch on/off times, or Monday to Friday only, is there more than one source ... Talk to neighbours and even set up RSL for them to see if they have issues too.

Being in a block of flats does not make it easier. Is there a services room where everything comes in and distributed?

The telephone lines for the block arrive externally, run as a single bundle up to an external junction box at 1st floor level, from which the individual flat's lines are then distributed.

Electricity supplies arrive to a communal area under the ground floor stairs where meters and cutoffs for each flat are located.

It's a 1930's construction, so no modern comms / utility room as such. Although I do have the right to keep a coal bin in the communal hallway according to my lease docs

How close to that junction box is your master?

There is always the possibility that a neighbours line is picking up high levels of noise from something in their flat and then there is crosstalk from that line to yours.

It's about a 5 metre run from the external junction box to my master socket.

At least it does not go through another floor or another property ...

Is there anything along that run such as a plasma TV that might cause electronic noise?

I don't think so. But I have no idea what gadgetry the neighbours all have.

For all that have been spectating my tumultuous noise margins, I thought it only fair to post a follow up.

As suspected there was more than one culprit.

This >30dB hit...
http://i1066.photobucket.com/albums/u402/premmy9912/...

Was caused by an electric powered cement mixer a neghbour's contractors had running.

Once that went away, I was getting ~4.5dB dings from a closer neighbour's kitchen fitters tile cutting. They were using what I would call an angle grinder to chop tiles (at least the motor had the same clackity noise to it) - they spun it up, the NM took a hit. They seem to have gone to the painting phase and 9Mbps / 6dB seems the norm. Bit odd that the Sky DLM never seemed bothered to move the line from a target 6dB.

Perfect storm of poorly maintained equipment.

Those must have been some pretty badly maintained or cheap pieces of plant! Did you make te neighbours and contractors aware of the issues the were causing and that they were technically causing a nuisance?

I have recently been using a tile cutter - 8" diamond disc that takes a few seconds to spin up - no problems even though just a few feet away and my cement mixer, which like all is abused, does not, as far as I know give problems either.