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[rwm32]

Can it be correct that no-one can officially approach a 3rd party who is causing intereference? (Like broadcasting on reserved frequencies is not allowed)

Yes, you can contact Ofcom directly. In my experience, they will investigate pretty quickly.  You need to give them a good idea of which frequency ranges are involved.

rwm32

[neilgl]

Hi all,
if my ADSL is split into bins (buckets) at the usual frequencies:
0-4 kHz, voice.
4-25 kHz, unused guard band.
25-138 kHz, 25 upstream bins (7-31).
138-1104 kHz, 224 downstream bins (32-255).

then what frequency of noise am I looking for (out in the streets) ? (138kHz to 1104kHz is a pretty wide range)
Do I have to look at each bin's centre frequency in turn?

An AM Radio tuned to 612kHz won't do it?

I am going to unplug my BT Home Hub 2 and put in my BT Voyager 2100, then use DMT tool to look at gaps. That may give a clue.

Regards,
Neil

[roseway]

The frequency isn't critical. The interference probably won't be a single frequency but a mish-mash of various frequencies and harmonics. If it's there to be found, then tuning in between the receivable medium wave stations will probably pick it up. Remember that the radio aerial is directional - rotate it for the strongest interference signal, then the source will be somewhere on a line at right angles to the axis of the radio.

[rwm32]

Using DMT Tool will certainly help with diagnosis of external RF interference and narrow down what bands to focus on.

The attached screenshot shows typical MW-freq interference from Radio5Live on 909kHz and Club Asia (a local station) on 963-972kHz.  This is obviously significant interference, taking out several hundred kbps of bandwidth.

You can also see lots and lots of lesser interference on many frequencies from around 552kHz and up. To take two examples: Kismat Talk Radio on 1035kHz and Talk Sport on 1053kHz.

Unfortunately, (to paraphrase a nice letter I had from Ofcom) authorised MW broadcasters are classified by Ofcom as the primary users of the spectrum between 500kHz and 1600kHz. ADSL Broadband using these frequencies is classified as a secondary use "and has no protection".

That's life.

rwm32

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[waltergmw]

In view of RWM32's comments and Roseway's thoughts that it's likely to be a mishmash of noise, you might find it more profitable just to chase the bursts, which the modem aggregates into its single noise margin figure, when they happen. The following Routerstats picture was caused by crosstalk from another line where the drop wire ran parallel for more tham 10 m close to PIR and security wiring and then had about 7 m of vertical open-ended flat twin attached. In this case a wireless might not pick anything up directly as both the source and the secondary conductors were some way off, and happened to be screened by thick buildings on a steep hillside. The actual cross-talk pick up could only have happened in the BT 66 box or in the cable running down to an underground cable joint, or in the pairs on their way back to the exchange via the street cabinet.

Kind regards,
Walter



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[grantura]

Hi Neil,

I'm in Milton Keynes too and have been having similar problems to yours for some considerable time although it has recently got worse. In my case I believe it is caused by crosstalk from the leased lines from my local pub causing my modem to loose sync at opening time and to reconnect at a reduced Noise Margin (up to 5 db) until closing time. You can see some of the details on the bb4mk web site at:
http://www.bb4mk.org/bob1.htm

BT are investigating through bb4mk's contacts within BT

I think my problem in local to the Loughton grid square, are you nearby?

Bob

[neilgl]

Hi all,
Bob - I am in Old Farm Park, so not on your grid. I had seen your site before - nice work.

All, yes I will look for bursts and put DMT on the old router (can't get son off World of Warcraft atm)
The radio channel stuff is interesting but has probably been around for years so its not that.


Regards,
Neil

[kitz]

On a side note

>> bb4mk

Theres a blast from the past with the bb4[insert_town] sites!   
I'm afraid ours for the exchanges in our area has long gone, but the 2 remaining campaigners are admin on here.
MK has always had special interest because of its problems so its good that its still alive and kicking.   Ours also had special interest from BT at one point because of one of the exchanges which had problems when it went live.

Thanks for posting and I hope they manage to get to the bottom of it for you.  REIN can be a PITA to resolve sometimes.

@ neil

Hope you manage to spot something with DMTtool

[grantura]

Bob - I am in Old Farm Park, so not on your grid. I had seen your site before - nice work.

Neil - Its not my site, I am the local co-ordinator for this part of MK but if you don't get any results on your problem, you might find an email to Nick Hubbard might be able to get some internal support from BT. (see bb4mk for the address).

On a side note

>> bb4mk

Theres a blast from the past with the bb4[insert_town] sites!   

We still meet occasionally but as BT have addressed most of  the not-spots we have turned our attention to trying to improve the performance of the  poorly served areas of MK (some users can still only get 256 kbps). Unfortunately I expect that the layout of the exchanges in MK will mean that some parts will not see high speed broadband until fibre to the cabinet can be rolled out.

Bob

[neilgl]

Hi all,
latest update from BT Retail (complaints manager?) as at 11th June - BTW are "working on it".

I have been doing some real work so not on the DMT / radio just yet...

Just think, only 4 weeks more to go before Ofcom complaint can be raised...

Regards,
Neil

[neilgl]

Hi all,
DMT used at 0838 today (13th June) when line sync was low (832kbps)
Prior to that the sync had been 2400kbps for 6.5 hours, then at 0728 it dropped.

The DMT seems to be showing at gap at 600kHz and low SNR per tone on all frequencies between 518 and 656kHz
I'll take another shot when the line is up at high sync (around midnight tonight)

Any ideas?

Regards,
Neil

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[neilgl]

Hi all,
did a DMT test today when it was running OK (2144kbps)
(It has been at over 2Meg for 7 hours, now 896k and is following the normal pattern...)

How does the attached look?

I can see that the frequencies affected are all between 242 and 724kHz.

Regards,
Neil



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[neilgl]

Hi all,
latest update: It is still not working. Still cannot get a straight answer from BT and BTW.
Anyway, I got a second phone line installed (Sky offer free for 1 year with TV) and now have Sky base (free) broadband (up to 2Meg) on it.
I can compare the two.
Result: BOTH phone lines are affected by the "noise" in the same way at the same time (i.e. disconnect and resync at low speed) BUT the Sky line recovers throughput much quicker than BT when the sysnc speed goes up - no waiting 12 hours for RAMBo on BT.
The help desk at Sky told me they do not use a rate adaptive monitoring system like RAMBo.
Regards,
Neil

[kitz]

The last DMT graph looked fine and I couldnt really see anything much wrong on that. There are a couple of tones with lower SNR, but at a rough guess that is only costing you approx 40-50 kbps overall on that particular graph.
Looking at the previous one it does seem that noise is generated somewhere at tone 450+. Some lines are more noisy than others, and obviously this has more impact on a longer line like yours :/

Not good that the new line is also affected.. so it could be something to do with the distance and perhaps some EMI they pick up just about anywhere between you and the exchange.  Im guessing, but judging by the spread it seems low level but when it occurs it seems to spread over a wide ride.  This will play havoc with bit loading/bit swapping and the line will drop when you run out of spare bins to swap to.

>> The help desk at Sky told me they do not use a rate adaptive monitoring system like RAMBo.

Although they do have some form of profiling..  they dont do IPprofiles like BTw. The IPprofile system is what is actually getting the higher speeds back immediately once your line recovers.  Many people in your situation find that LLU works better because they arent waiting days for the system to go back up to a higher profile again.

[neilgl]

Hi all,
latest update: It is still not working. Still cannot get a straight answer from BT and BTW.
The loss of sync and low connection speed occurs at particular times of day.

An Openreach engineer came on Monday, tested the line (again) all OK. Of course during the day the "noise" is not present and it was synced at 2496kbps.

16/7 Phoned Otelo to raise a complaint as 3 months have now elapsed (Ofcom minimum time between complaint and when they can take up the case). However, Otelo said send a letter to BT in Durham, they then have 14 days to respond, then Otelo take up the case. Pity it did not say that on the Ofcom or Otelo web sites as I would have done it 14 days ago...

Coincidentally that day another Openreach engineer came to my house at 11:00 and tested the phone line (again) all OK. Of course during the day the "noise" is not present and it was synced at 2432kbps.

Later BT India phoned me and said a REIN engineer will be at my house on Friday between 6pm and 8pm, when the loss of sync/noise occurs. OK I said. No-one turned up between 6pm and 8pm. The line droped at 17:09 as usual.

I called them and they said a REIN engineer will be at my house Saturday (today) between 6pm and 8pm AND Monday 6pm 8pm.
I'll let you know...
Regards,
Neil