It just goes to show you can't be sure about interference without measurement. Unless a VFD/inverter explictly states it has built in filters it will need external filters to bring emissions within limits.

Robert G8RPI.

Sounds like its filters (capacitors) on the EHT inverter had died of old age and it was putting noise on the mains that then got into the phone line perhaps due to a getting through the modem psu. Kind of sloppy of BT not to have looked at it earlier.

Interference from all sorts of things is a problem for meodems, not necessarily cutting out just reducing speed. Mobile phone base stations signals don't help. I've seen a fish tank heater timer give wifi problems reported as intermittent connectivity. If the owner had been more observant they would have noticed it was only starting at 2pm every day.

I imagine there is a lotof potential for eg a home made rotary converter, failing VFD capacitors, worn brushes on a drill etc, to put noise on the mains that can then get into places it shouldn't.

If you want to get a feel for what noise is around from a motor the simplest thing is a battery long or medium wave radio.

"We'd just advise the public to make sure that their electric appliances are properly certified and meet current British standards," she said.

That sounds a bit daft – it means that we have to change everything for the latest BS. Do I have to upgrade my 1932 Austin 7 to the latest emission regs ? Ahem, I think not.

When I fitted the VFD controlled three phase motor to the Tom Senior, I first chose one with filters for interferance supression. The Vfd is in an earthed steel box, and all the cabling is screened, including the low voltage control wiring. We have not noticed any problems with VHF and DAB radio signals, and the wireless router in the workshop runs as expected.

I had been initially concerned by the manual mentioning an earth leakage when using the filters, but there has been no tripping of any RCD when the mill is in use.

I sort of agree but I think it's more likely that older equipment would be grandfathered until their penetration comes down to, what …. 10% ? ; 5% ? and then made illicit.

I also think that the person concerned was pretty dumb. I'd have said (to the cable/internet people) "until you can show me that it's illegal I'll continue to use it …… of course you could always buy me a new, modern TV (and dispose of the old one)" Which would be by far their cheapest option (not to mention good publicity).

Old equipment not meeting current standards is usually allowed to fade away. The chance of it causing a problem decreases over time because fewer and fewer people own one. But if an old telly interferes with a service, then it can be shut down, provided someone is annoyed enough to trace it. There will be a rapid response if it wipes out airport communications, the military or an emergency service!

Not difficult to think of exceptions,usually safety related: weapons, certain chemicals, pollution, and use of the radio spectrum come to mind, but chopping stuff off at the knees isn't common in the UK. Not all situations permit shades of grey – if the country decided to drive on the right, there wouldn't be a transition period!

The problem in Wales is likely related to the limited error correction scheme used by some transmission systems.

To guarantee reception, it's necessary for sender and receiver to acknowledge receipt resulting in a constant exchange of messages confirming all is well. As this is wasteful and unnecessary inside a normally reliable network, it's common to use a less perfect scheme called Forward Error Correction. In FEC data is packaged into blocks, arithmetic applied, and magic numbers added allowing the receiver to detect an error in a block with a good chance of correcting it from the magic numbers. Works very well up to a point, but serious noise can mangle blocks so badly the contents can't be recovered. Annoying when it happens to one user, very annoying when if effects everyone, and the whole network can collapse if control information is damaged.

Some sympathy with BT, though one might ask why their local team doesn't have a spectrum analyser, and why it took them 18 months to get one from HQ on site. Interference is so common it's strange the problem wasn't diagnosed earlier : I suspect fumbling rather than this being a technical problem.

Dave

Dave/SOD,

I understand where you are coming from, but somehow I doubt if the MSM would take kindly to big brother coming down heavily on to a pensioner who was unaware that his tv was causing a problem. It also suggests to me that the tv concerned may be faulty in which case the owner should have been advised to have it repaired, not agreeing to not use it – unless it was an agreement to not use it until it had been repaired. Furthermore, I would suggest that the onus is on the designers of the equipment being interrupted to ensure that their equipment is hardened against such interference – unless of course, they are going to pay to have all the interfering equipment repaired or overhauled. There is, of course, a precedent for this, not an exact precedence I admit, but near enough. Think back to when Channel 5 started up transmitting on (I think) Channel 35. In that instance the broadcasting company was required to pay for the retuning of all the VCR's away from transmitter Channel 36 to avoid interference.

I must admit there is precedence the other way: witness the change to so-called digital tv when everyone was required to update their tv reception equipment, but in that instance it was either do it or lose your tv service – there was no threat of big brother coming down heavily if you didn't comply.

I would still like to know more about how switching a tv can cause such a large transient as to knock out broadband. It suggests to me that the broadband designers have not properly hardened the broadband distribution equipment.

Incidently, whilst writing the above, it has occurred to me just what are we talking about here. Are we talking about FTTC, ie the system whereby a large green box distributes broadband around the locality? Does anyone know?

Peter G. Shaw

I'm surprised that domestic microwave ovens don't cause more issues with domestic WiFi installations. Given that the leakage from an 800W 2.4GHz heating device might well overwhelm the output from a 20mW 2.4GHz WiFi transmitter.

We had a construction Site on the Isle of Grain, in Kent, that I'd installed both the wired and wireless networking in. The folk complained that every now and then, the WiFi to their laptops would drop out for a little while… When the laptop is set to prefer the 5GHz frequency band (usually better) and a ship goes past with it's (5GHz) radar belting out a few KW, the WiFi access points would shut down to avoid interfering with the ship's radar…

Ha ha, I liked the confidence of the last para of that report. It may certainly improve the situation but they omit to inform that the fibre optics will not necessarily help individuals, as all the houses will still be fed by copper, from the optical connection to the village….

.

A nice, concise, summary … Thanks, John

MichaelG.

Naughty Lightening, recently had a blown ASDL filter AND BT telephone base unit K*******d by an "Instantaneous" local flash/bang.

Regards Ian.