Broadband interference

[number 7]

Has anyone ever heard of low-voltage external lighting systems causing interference with broadband connections? Having had a problem with a transformer earlier this year causing my Plus net connection to drop continuously, I've sidestepped the problem by leaving the light off. However, the problem has re-appeared in the past few days - connections last for a couple of mins. and then drop. Changed modems, filters, plugged into main BT socket, and disconnected all other telephony. And the problem continued until I asked my neighbour to switch off his outside Christmas lights this morning. Suddenly, everything works ok. Even stranger, the neighbour on my other side also had his broadband (Wanadoo) connection down for days, only re-instated when the Christmas lights went off. Surely the underground BT cables should be insulated against interference? Any ideas whilst I'm waiting for BT to get back to my ISP?

TIA

7.

[_dobbo_]

Initially sounds unlikey, but then thinking about it I've heard all sorts of inteference on phone lines in the past.

Sounds like a midnight excursion with some insulated wire cutters is in order

[Pat H]

number 7 said:

Has anyone ever heard of low-voltage external lighting systems causing interference with broadband connections?

Number 7, I owe you a pint.

I have experienced the most dreadful problems with my Wannadoo broadband connection over the last ten days.

I have made about a dozen calls to Wannadoo technical support, reinstalled the modem software, changed filters, leads and generally buggered about with very little success.

I thought I'd sorted it this morning with a couple of hours of uninterrupted browsing, only to try again tonight and find that my link is constantly being dropped a few seconds.

Having read your post, I went out to the garage and unplugged my low voltage Christmas lights.

As if by magic my connection has been restored and is now working faultlessly.......

Cheers

Pat

[GreenV8S]

That's wierd, any idea what the mechanism is? Something to do with the long low voltage wire runs acting as a transmitter for the mains hum, perhaps?

[polus]

That is a little werid, however cheap tacky mass produced electrics arnt best known for EMC

>> Edited by polus on Sunday 18th December 19:48

[number 7]

Pat H said:

number 7 said: Has anyone ever heard of low-voltage external lighting systems causing interference with broadband connections? Number 7, I owe you a pint. I have experienced the most dreadful problems with my Wannadoo broadband connection over the last ten days. I have made about a dozen calls to Wannadoo technical support, reinstalled the modem software, changed filters, leads and generally buggered about with very little success. I thought I'd sorted it this morning with a couple of hours of uninterrupted browsing, only to try again tonight and find that my link is constantly being dropped a few seconds. Having read your post, I went out to the garage and unplugged my low voltage Christmas lights. As if by magic my connection has been restored and is now working faultlessly....... Cheers Pat

Glad to be of service.
Obviously, turning the lights off is not a proper solution. Surely mains/lv transformers are built to standards which will ensure little or no generation of interference? And how does any interference that they mad create penetrate cabling buried underground which presumably is also shielded? Or is it "getting in" downstream of the point at which the BT cabling enters the house? I'm still waiting for feedback from BT via my ISP. In the meantime, one of the tests which Plusnet has carried out is : Upstream DSL loop loss 25db margin 27 db, downstream DSL loop loss 40 db margin 14 db. Can anyone tell me if this is good or bad - to a non-techie like me, one of these results looks like it's outside of the set parameter?

7.

[zumbruk]

number 7 said:

Obviously, turning the lights off is not a proper solution. Surely mains/lv transformers are built to standards which will ensure little or no generation of interference? And how does any interference that they mad create penetrate cabling buried underground which presumably is also shielded?

It's almost certainly a switched mode power supply, and the interference is getting into the mains power supply. You can buy "low pass" mains filters to eliminate this. The overhead phone lines are not shielded - this would likely cause more problems with earth currents than it would solve.

Domestic electronics are generally built down to a (very low) price, and if they can omit a 5p capacitor, they will, and take the chance with interference.

[Le TVR]

number 7 said:

Has anyone ever heard of low-voltage external lighting systems causing interference with broadband connections?

All broadband systems, DSL, ADSL, BPL etc all operate at radio frequencies. This would be fine if all the connecting cables were coaxial screened types. They would then be immune to RF interference.

However, all these systems use unscreened cables - especially the parts inside your house. So all broadband modems are effectively connected to big receiving aerials.

Bring along something that transmits (although in this case a switchmode transformer shouldnt really) and interference WILL happen.

And by the same reasoning, your broadband modem is very probably transmitting cr@p at some other RF frequency because of its unscreened cable connection.

Cuts both ways, because both are cost-cutting examples of poor engineering.


(oh yes, I'm a professional RF engineer and EMC consultant.....)

[number 7]

Le TVR said:

(oh yes, I'm a professional RF engineer and EMC consultant.....)

Thanks for the input Le TVR. From what you say I'm probably going to get the fob-off from my ISP and BT - they all do that sir???? Is there actually anything that I can do, other than switching off my own lights and asking neighbours to do similar, which is hardly a solution?

Nice "S" BTW. Must be pretty rare where you are?

7.

[Le TVR]

Unfortunately there is a lot of 'pass the buck' between those that should have immunity and those that shouldnt radiate. TADTS doesnt exist- its the 'others' fault........

Dont suppose that screened phone cables exist?? didnt think so....


There are a few S in France but probably less than 10.

[polus]

Another reason I love NTL cable broadband, upgrading to 10Mb for free (admittidly I pay £25 per month but Ive never hit a bandwidth limit), screened coax like a mofo and a static IP (or close to)... <smug loving ntl mode = on>

>> Edited by polus on Monday 19th December 22:53

[_dobbo_]

OK, you can't get screened phone cables but would wrapping the modem cable round a bit of ferrite help? Certainly removed all the inteference on our old work phones, back in the olden days!

[bigdods]

Possibly related - In my past life as a PC engineer visited a customer where one bunch of PCs were running slow on the network. No matter how they connected the network cables or moved them around nothing changed. I pop in and first thing I notice is that I get a healthy shock off the back of the first PC I touch. Whip out the faithful multimeter and theres near on 200VAC on the back panel. Hmmm. Check a few others. All doing something similar. Hmmm. Discover all affected PCs connected to the same 4 way block where the neon power indicator has blown and is shorting earth to live pushing a voltage across the PC cases and through the earth thereby buggering up the network. Remove 4 way block, all speed restored.

Only thing here is Im not sure if these low voltage christmas light kits are earthed at all so this could be a red herring....

Id probably be inclined to go with the earlier suggestion - xmas lights sticking crap back down the mains thereby raising interference, possibly in the DSL modem itself. This could be easily proved if you can borrow a battery backup/UPS unit from someone, then run your DSL modem/router off it and see if the problem goes away...



>> Edited by bigdods on Tuesday 20th December 10:07

[sp60]

number 7 said:

Glad to be of service. Obviously, turning the lights off is not a proper solution. Surely mains/lv transformers are built to standards which will ensure little or no generation of interference? And how does any interference that they mad create penetrate cabling buried underground which presumably is also shielded? Or is it "getting in" downstream of the point at which the BT cabling enters the house? I'm still waiting for feedback from BT via my ISP. In the meantime, one of the tests which Plusnet has carried out is : Upstream DSL loop loss 25db margin 27 db, downstream DSL loop loss 40 db margin 14 db. Can anyone tell me if this is good or bad - to a non-techie like me, one of these results looks like it's outside of the set parameter? 7.

None of the low voltage tree lights I have used have ever had a transformer, they simply connect the bulbs in series rather than in parrallel, thus dividing the available voltage between the bulbs. Maybe this is why they cause such a problem, but not being an expert in these things, I cannot comment. Maybe you should put the lights on a line filter rather than the affected devices, this may well stop them from affecting the supply as a whole.

Your DSL settings look a bit on the low side, but still within parameters. AFAIK the lowest reliable SNR(margin) is around 10db. Our office is on the limit, distance wise from the exchange and we consistantly run at between 12-15db SNR with a loop att. of a pretty consistent 60db. We only started having problems when one of the lines dropped below 10db SNR, but that was due to a very long length telephone extension cable being plugged in. With SNR at 14db though, you are going to be much more suseptable to problems from interference.

[Plotloss]

You can run POTS over STP which would shield that element at least.

Mind you, with shielding comes install foibles...

[si_j]

[quote]Upstream DSL loop loss 25db margin 27 db, downstream DSL loop loss 40 db margin 14 db. [/quote]

14db margin is on the limit for a 1Mb connection, should be fine for 512K. Also need to factor in if your on IPStream or Datastream.

Xmas lights are a well known cause of problems (along with hot tub Jacuzzis), apparently "CE approved" lights are ok and not so much of a problem.

[number 7]

si_j said:

14db margin is on the limit for a 1Mb connection, should be fine for 512K.

How about for a 2MB connection, which is what I have?

7.

[si_j]

2Mb - right on limit. probably experiencing dropped connections etc, no wonder your chrisse decorations are playing havoc with your BB.

Rule of thumb = Higher the Margin the better, you should be over 20 for a good stable 2meg connection.