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Severe crosstalk started 24 hours ago

andywright
Dabbler
Posts: 17
Thanks: 1
Registered: ‎23-10-2008

Severe crosstalk started 24 hours ago

I wonder if anyone else has had this problem? About 24 hours ago my router started resyncing over and over. I managed to track the problem down to the neighbour's adsl - the modems fight each other, when one starts training it kicks the other off and then they fight each other. We've had to switch one of them off to get the other to settle down.
This has only started happening very recently and I've tried various combinations of different routers on each line to no avail. Interleaving is enabled on my line and I've requested PlusNet enable it on the other if it isn't already. No idea if this will help but I just can't face having to try to report this via BT.
If the interleaving doesn't fix it (and I don't really see that it could, given the problem has only now manifested after 3 years of us both having adsl), does anyone have any ideas how I might go about getting this fixed?
Both modems are connected to filtered faceplates right where the line enter the buildings so there's nothing more I can do to improve the line quality from this end....
21 REPLIES
Community Veteran
Posts: 3,366
Thanks: 15
Registered: ‎06-04-2007

Re: Severe crosstalk started 24 hours ago

To be clear, are you saying after some many months of the three of you using the ADSL modems, this has just started to happen ... well something has changed and it is most likely to be one of the phone lines breaking down causing the exchange to increse its output power to compensate. So, do you both know what your attentuation and noise marging values were before the problems started? What are those values now? If one of them has changed signifcantly, that is the one which is likely to have a problem.
Also, my line characteristics have changed since BT fixed a line fault many months ago, I have list 1Mb of speed due to this, BT tell PN this is acceptable and PN just fold in response. Sad
You could be in the same postion I am afraid.
SW.
fixed typos oct/24
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3Mb FTTC
https://portal.plus.net/my.html?action=data_transfer_speed
pierre_pierre
Grafter
Posts: 19,757
Registered: ‎30-07-2007

Re: Severe crosstalk started 24 hours ago

could also be something simple like two are trying to use the same channel
Community Veteran
Posts: 19,101
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Registered: ‎31-08-2007

Re: Severe crosstalk started 24 hours ago

I would raise tickets on both accounts and cross refer to each ticket from the other and come back here and post the ticket numbers for James or someone to take a look.
andywright
Dabbler
Posts: 17
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Registered: ‎23-10-2008

Re: Severe crosstalk started 24 hours ago

ok James if you're here - the 2 ticket numbers are 26761308 and 26761599
To summarise - 2 adsl accounts, been installed for 3 years and co-existed happily. As of late Wednesday evening the routers began fighting each other. One syncs, the other starts syncing and kicks the first one off. Repeat ad-infinitum.
Both routers are connected to filtered faceplates where the line enters the buildings. I have tried various combinations of 5 different routers (Billion, Netgear, Thomson).
BT have recently replaced a large run of overground multicore, but this was a few weeks ago and until now had been running ok.
Line stats haven't changed - both are around 57db attenuation downstream and sync around 3400 to 3800 depending on time of day.
The router on ticket 26761599 is currently switched off. Without doing this it's impossible to get either to connect.
Community Veteran
Posts: 3,366
Thanks: 15
Registered: ‎06-04-2007

Re: Severe crosstalk started 24 hours ago

Any progress on this one ...
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3Mb FTTC
https://portal.plus.net/my.html?action=data_transfer_speed
andywright
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Registered: ‎23-10-2008

Re: Severe crosstalk started 24 hours ago

Quote from: godsell4
Any progress on this one ...

Yes. And No. !
PlusNet have been really helpful and booked a visit by a BT Broadband engineer to look at both lines. However when he arrived he only had a fault logged against my line and was reluctant to set foot into the neighbour's house. I explained the problem and my suspicion that it was high-frequency crosstalk on on our lines. He looked at me blank, saying something along the lines of  "It sounds like you know more about how adsl works that I do".
He then proceeded to blame the problem on, amongst other things, the fact the neighbour's line is rubbing slightly against the side of my house, and the that their wiring runs close to some mains cabling. I couldn't see how these could cause two lines to suddenly start interfering with each other but I kept quiet.
With the neighbour's adsl still turned off he plugged in his test router & laptop into my line and got sync (no surprise there - I'd told him either of our routers would work in isolation), and proclaimed everything to be ok! I managed to get him to stay put while I turned the neighbour's router on - and as soon as he synced his test box it kicked the neighbour's off. However, because his fault was logged against my line and his test box worked ok, he said everything was fine and that was all he could do.
I'd given up hope that he'd be able to do anything useful so I let him go.
Back to my box of spare routers, I kept trying various combinations on both lines until I hit upon a pair that would run without fighting. Turns out a Billion 5102S on my line and a BT 2110 on the other works ok, albeit with a reduced sync on the BT router (2100bps compared to my 3360).
It's been stable for a few days so I'm leaving it at that. Unless the lines degrade further and make these 2 routers unstable I doubt I'll get any joy out of BT.
Fingers crossed !
itsme
Grafter
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Registered: ‎07-04-2007

Re: Severe crosstalk started 24 hours ago

It sound more like a high resistance short between the 2 pairs. With your neighbours help I would suggest dialling 17070 on phone 1 and select option 2 (quiet mode) then with someone listerning on phone 1 go to phone 2 and again dial 17070 and see if the the STD number annoucement for phone 2 can be heard on phone 1. You could also select option 2 on phone 2 and speak to see if you can be heard on phone 1.
andywright
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Registered: ‎23-10-2008

Re: Severe crosstalk started 24 hours ago

Quote from: itsme
It sound more like a high resistance short between the 2 pairs. With your neighbours help I would suggest dialling 17070 on phone 1 and select option 2 (quiet mode) then with someone listerning on phone 1 go to phone 2 and again dial 17070 and see if the the STD number annoucement for phone 2 can be heard on phone 1. You could also select option 2 on phone 2 and speak to see if you can be heard on phone 1.

Thanks but already tried that  Smiley
I did also get the engineer to put a tone on one line and 'sniff' and listen for it on the other  - nothing at all, so any crosstalk is probably only happening at much higher frequencies.
MickKi
Grafter
Posts: 543
Registered: ‎30-09-2007

Re: Severe crosstalk started 24 hours ago

It does indeed sound like a high frequency cross talk.  It is most likely related to a fault on the insulation of the wires.  It seems that they may/might be under tension and over time the insulation has worn/broken down to allow certain frequencies to transfer across.  If this carries on it should eventually lead to cross talk at audible frequencies, at which point BT may transfer one of you on another pair.  A lot of assumptions here.  Anyway, if you report it again and request that a Broadband Openreach engineer visits to check an intermittent fault, then they may send someone who qualifies above the entry level of a muppet and who should carry on the necessary checks to verify the problem.  The solution I fear may depend on them having a spare pair in the multicore.
itsme
Grafter
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Registered: ‎07-04-2007

Re: Severe crosstalk started 24 hours ago

Insulation do not stop inductive or conductive crosstalk. If it did then they would be no need to go to expensive lengths to stop this. Also this is the reason twisted pairs are used as the crosstalk would be picked up on both wires and cancel each other out. In my opinion the problem is more likely bad jointing in the new cable. But how do you prove this to BT if their are not prrpared to investigate both faults at the same time?
itsme
Grafter
Posts: 5,924
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Registered: ‎07-04-2007

Re: Severe crosstalk started 24 hours ago

As the OP is switching routers/modems around and seem to be responsible for the neighbours setup could the problem be that the OP has accidentally setup the modems/routers up with the same account? 
MickKi
Grafter
Posts: 543
Registered: ‎30-09-2007

Re: Severe crosstalk started 24 hours ago

Quote from: itsme
Insulation do not stop inductive or conductive crosstalk.

Physical proximity between wires is necessary for either inductive or conductive noise transference to occur.  The insulation provides a physical separation at a specified distance, which when reduced can increase the probability of crosstalk.  As it is more likely for the insulation to break down at one only wire the circuit is unlikely to be balanced.  In addition, any phase difference between the signals on each wire in the pair will also cause noise.
Ultimately, insulation is there for a reason - to act as a dielectric material.  If BT have over-meggered the wires to ensure that there is no continuity, they could cause marginal insulation to break down a bit more and generate cross talk.
Your comment for the same user details being entered in both routers came to my mind too (the fault behaviour is typical of this) but I assumed that the OP would have checked this out amidst his many trials & errors and so should have PN.
Edit:  Conductive noise is totally dependent on the integrity of the insulation and unlike inductive loads it cannot be balanced out by the twists in the pair.  Also, in the case of inductive noise, I assume that the pitch of the twist in the pair is tuned to the voice frequencies rather than the higher DSL frequencies and so may be less effective in cancelling out high frequency noise.  Anyway, tension in the cable and bending that alters the pitch of the twist can also have a detrimental effect on balancing out noise, besides ultimately leading to chaffing and insulation breakdown.  In conclusion, BT may have botched up the installation - but checking out username and passwd should be the first port of call.
HTH.
andywright
Dabbler
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Registered: ‎23-10-2008

Re: Severe crosstalk started 24 hours ago

Quote from: itsme
As the OP is switching routers/modems around and seem to be responsible for the neighbours setup could the problem be that the OP has accidentally setup the modems/routers up with the same account?   

Nope  Cheesy
Often wondered if that would work actually, can you log a router into PlusNet with a valid account + pw, but on a line other than the one the account is set up for ?

Community Veteran
Posts: 3,789
Registered: ‎08-06-2007

Re: Severe crosstalk started 24 hours ago

Yes.
The line will be "locked" to a particular realm (or set of realms) such as plusdsl.net.  However, any valid user from that realm will be able to log in from that line.
B.