'Interfering' BT Vision attracts campaigner glares Campaigners complaining about interference generated by BT's Vision product have financed independent tests to show that the kit BT is pushing fails to conform to the appropriate EU standards, prompting a complaint to trading standards officers. Shortwave radio users have been complaining for a while about interference …
Analogue radio is going to be shut down in a few years, why would they bother doing anything about interference to reception of it. As long as DAB is not affected they will be happy.
Of course there are many radio hams (myself included) that will not agree with this -- I often listen to short wave broadcasts and would be very annoyed if I was prevented from doing so due to "legal" interference. At the moment there is no problem in my area as BT can't even provide broadband let alone vision!
I was a "victim" of this issue and logged a complaint with Ofcom.
However, before the field agent was scheduled to visit, my neighbour agreed to remove the devices from his home, for which I am very grateful!
If you are a radio amateur, enjoy listening to shortwave broadcasts, or are a scanning enthusiast, a neighbour getting a pair of Comtrend PLT devices means it's very likely that you will be unable to hear anything apart from this digital noise on most of the HF spectrum.
They need legislating against, soon!
/Paris, because she might enjoy being interfered with.
All traffic has the option for 128bit AES encryption so, no, it shouldn't be vulnerable.
Personally I love the homeplug kit - it's easily one of the most effective and least hassle devices I have.
Although I have some (extremely small amount of) sympathy for the shortwave radio enthusiasts they don't help their cause by making stupid arguments like 'it might interfere with military transmissions'. I'm sure that'll be a huge problem, if there's ever a chinook 200m from my house..
This equipment has been causing interference on my CB and is very annoying. Unfortunately there is nothing we can do as CB users as we don't pay for a licence, therefore we can't complain to OFCOM (as far as I know).
Well done HAM users. Lets see whether the toothless giant that is OFCOM can do battle with BT and win.
nope, never mind.
The article seems to imply that the device causing the problem here isn't the Vision box, it's the Powerline adapters. These are just 3rd party branded devices, not really BTs responsibility. They'll just switch vendor and carry on regardless. The problem was probably that BT went with the cheapest adapters they could find, rather than decent quality ones.
My wife used to listen to French radio on Long Wave until terrible interference made it impossible to listen to. When we researched how we could get BT/Offcom to investigate and stop the interference we discovered that they will only take action if the interference affects FM radio transmissions.
As Short wave transmissions are AM/SSB then I don't think they stand a chance of getting anything done, especially as Offcom use BT to do the technical investigation work.
The tests carried out in EMC test houses show that the un-notched signals are about 28-30dB above the EN55022 Class B limits. The modulation format used is OFDM, the necessary signal:noise ratio to get acceptable error rates is about 20-25dB. This suggests that if a PLT transceiver has its output power reduced so that it meets EN55022, the signal:noise ratio would be down to well below the noise level, resulting in no comms at all.
You can see why the PLT companies don't want this explored further, and recently they were prevented from pushing through a change to the standard in the CISPR 22 committee that would have increased the mains test network defined LCL from 6dB to 24dB (that's essentially saying that mains wiring is much better balanced than reality. As a comparison, CAT5 cable has an LCL of 60dB, so is very well balanced, which is why Ethernet cables don't radiate much at all. It is the unbalance in the mains wiring that causes the RF to be radiated, you can't make balanced mains because of the number of spurs, light switches and the variable termination due to the wide variety of mains-powered equipment.
There is one more aspect to this. If a manufacturer can't get a piece of kit passed by a test house, they can use the Technical Construction File route. The TCF is essentially a report that details how a piece of equipment is built in order to pass (whether it actually does or not), one then can self-certify and never actually submit the equipment for testing. Once this is done, the CE mark can be applied and you can sell the kit it in any EU country. No country can then legally remove it from the market without a lot of effort and expense (EMC testing costs thousands of pounds for a couple of days in the test house) and there is no mechanism to revoke the CE mark where a TCF is created.
Radio amateurs are particularly vulnerable because they often operate with signals that are very weak, unlike broadcast stations which try to deliver a high enough signal level to overcome at least some local noise. That's why the PLT devices have notches in the HF amateur bands, but they are not really deep enough for a complete cure. Short wave listeners are trying to receive at frequencies where there are no notches, in many cases the PLT interference (which can be heard over at least 500m in lots of installations) is too great and they cannot receive any more.
Remember the the ionosphere only works for radio propagation over the 3-30MHz range, there are no other frequencies that can be moved to.
Essentially the regulators have dropped the ball over this one, with a bit of luck the chickens are going to come home to roost and the PLT manufacturers are going to find some chill winds blowing.
...or the house which is emitting the interference? I mean if the box is designed and implimented to EU standards regarding interference / emissions but the mains cabling in use in the property is causing the problems then BT and the manufacturers are home and dry aren't they?
Not saying it is right or fair but if the box isn't the root of the interference then it must be the person operating the box who is at fault yes?
OFCOM are useless..
As for us HAM's well.. As we may be about to lose 70cms (airwave) and are seen as old men in tweed jackets moaning about young peoples motorbikes causing interference with our valve radio, chances of anything good happening/coming out of this.. Nill.
I'm looking forward to the OFCOM ruling that tells HAMS to encrypt radio transmissions to save the spectrum... lol..
Sometimes I wish I worked for one of these organisations, then again would I be able to live with myself doing what they do?
The BT Vision kit was so noisy locally on the mains that my old hi-fi amp was almost unusable. Changing the network bricks helped and buying a mains filter extension lead (for audio, the other type were useless) has pretty much cured it. Bit of an expense for getting a free box.
The network bricks were a revelation though, can't see much point at home for wireless now. And the Vision box works well. Swings and rooundabouts, I suppose.
I'm interested if the PLT that the Comtrend unit uses (for better or worse) would have an effect on other users of PLT for data.
It certainly SOUNDS to be fairly constant traffic from the video clip.
Incidentally, the interference doesn't seem limited to the amateur bands - the video shows it affecting the internationally agreed 13m shortwave broadcast band which does have some users as its the longest range band not seriously affected by the sunspot cycle.
I hope Ofcom will make them sort it out!
Yes, even if the TV is a Dixons special, their feeder is forty years old and effectively a full line of point contact diodes, the aerial is composed mainly of aluminium [1] oxide and some idiot has installed a wideband preamp with a dynamic range in single figures. As you say, business as usual.
The question remains whether there is still anything on the amateur bands worth protecting, though.
[1] Oi! Mozilla! Screw your bloody half-arsed dictionary.
The number of official complainants was over 60 several weeks ago.
Only a fraction of BT Vision installations will be using these dreadful PLT devices.
A superior connection is always obtained by direct wiring,will save a bit of power
and avoid the BT customers being in breach of the non interference condition of
their TV licenses.
These units are normally left powered 24/7 and generate interference even when
the tv is off and the standby button of the PLTs is pressed.
I complained to Ofcom and after several months 4 pairs of units were removed.
3 were direct wired, the fourth was changed to WiFi.
All these BT Vision customers are getting good TV and my severe interference
problem has gone away.
I was affected by a fifth installation that went off for reasons unknown.
Weak intereference can still be heard from PLTs over 250 yards away.
Some common Symptoms of Radio Interference on Digital Equipment are "unwanted equipment lockup", "dropouts", "system reboots!" or "failure to connect to Service".
When more of the Radio Spectrum is used for Digital it will become more apparent in the same way that "TV Interference" was never expected to happen on the then new uhf 625 line system!
Conclusion Industry must keep it's equipments Radio Spectrums within the Alloted Radio Bandwidth!
Read the article again. This is to do with BT being one of the largest users of homeplug/powerline networking devices. The devices are ethernet bridges and you can plug any ethernet device into each end. BT will use devices at the cheaper end of the market, and these may well not be as accommodating to the spectrum used by shortwave radio.
In comparison to wireless adapters they're faster, more reliable and easier to use (unless you need to move the computer regularly to where there isn't a power socket ;) ).
Whilst I'm sure in the BT scenario it's simply a cost of support issue, anyone else explicitly buying a homeplug device usually has a good reason to do so. Wireless just isn't as good, and if it was simple to wire up the premise the person obviously would have done so - in newer houses it is an utter arse to try and fit network cables between different floors. There are huge floor grade chipboard 'floorboards'. the wall cavities are completely full and there is no floo. So either it has to go through the loft (may not be possible), around the outside of the house, tacked/stapled unattractively to a *lot* of walls, or replacing a load of skirting board.
Given those options, spending 50 quid and less than five minutes on something that just works and carries on working is very attractive.
When the Twin Towers collapsed, emergency comms went off-air, because the infrastructure equipment was on top of the buildings. Radio Hams from many states came in to support the relief effor and set up networks to route messages between emergency services and also for the Red Cross.
During the Boxing Day Tsunami, relief efforts were also assisted by Amateurs using Short Wave communications. Amateur radio is part of a great many disaster recovery plans worldwide.
You can call us luddites if you want, but in crisis situations, damn useful luddites to have arround.
--... ...-- / -.. . / -- ----- ... -. .-.
No surprise you had to post as AC old man. It isn't being a Luddite to expect interference limits to be respected, otherwise none of your shiny kit would work at all.These limits are relatively recent requirements, and have been drawn up because as newer systems have evolved it has been necessary to ensure that the EMC problems resulting have been kept under control.
PLT is one of those "because we can" technologies, and has driven a coach and horses through other people's allocations. It's only because of blatant manipulation of the regulatory process that this could occur, it was obvious to many of us that allowing self-certification for EMC testing would lead to trouble.
BTW, this works both ways, 400W PEP of HF SSB transmitted perfectly legally will usually cause a PLT system to fall over, funnily enough the pickup is caused by the unbalanced nature of the mains wiring that the PLT companies don't care about. What they sow, they shall reap!
Can stuff like this cause interference on DTV (i.e. Freeview)? My two tellies have started getting occasional dropouts for no apparent reason, (signal drops from 70% to 10% for about 1s) so was wondering where the interference may be coming from - could it be something like this? I have even had weird traffic on my car radio next to the house - like a police broadcast over radio 4.
We must be told!!!
Graham T
You are now entitled to interference free radio reception.
This is covered by EMC regulations 2006.
First make sure the noise isnt coming from your own house.
Listen to the station on a battery operated set,then switch your
electricity off at the main switch (on or near the fuse box) if the
noise stops it is something in your house!
If not Complain to Ofcom.
Ofcom DO NOT use BT to do interference investigation.
BT stopped doing this many years ago.
Legal licenced CB users.
You are entitled to reception free of PLT noise.
It does not matter that you no longer have to pay a fee.
Complain to Ofcom.
Best regards.
I'm afraid these gadgets are just far too useful to live without - I can't get decent consistent bandwidth to my living room over WiFi (possibly as a result of the fact that last time I ran a scan there were something like a dozen access points visible from my home, and that's only going to get worse...) but I've got a BT Vision box, an XBox, and a Wii happily sharing a single Comtrend 200 MBit ethernet-over-mains box through a single router. Moving the router's not an option because that's plugged into an old fashioned fixed "engineer installed" filter box in the office (where the bulk of the kit which needs to be plugged into it is anyway). Running CAT-5 around the place is a complete non-starter because my wife objects to exposed wiring and I'm buggered if I'm going to redecorate half the house to hide it.
I'm off to EBay right now to pick up a couple of extra boxes to go in the kids bedrooms and replace the (fiddly to configure and poorly performing) D-Link WiFi bridges while i still can...
Nah, can't be true. BT are one of the finest and most reputable communication companies in the world.
What's that you say. it is not 1989 and I have been in a coma for 20 years!
Wow your right, after further investigation I can now see that BT are a load of *&%^$$%*((*(
What's all this Crap called BT Webwise?
DRM (Digital Radio Mondale) won't work if interference levels are high either, this stuff will probably mean the end of long distance radio as Ofcom certainly won't take an interest in short wave listening either digital or analogue. The only time they will investigate is if you cannot receive TV or DAB as that's what your licence entitles you to receive, nothing else matters.
Funnily enough I have had to try for ages to send this as my 3G internet connection has given up -- it seems to get very unreliable about this time of day--- interference problem? unfortunately I can't get wired broadband -- exchange oversubscribed apparently
One hour later -- still no-go ---- trying again one an' a half hour later -- let's see
Ha!
So do you mind if I sit outside your house chatting on 433.920MHz with a mate locally and swamp your car remote control plipper so that your remote control doesn't work?
Or if I ignore your bleats of complaints because YOUR TV or whatever doesn't comply with CE immunity legislation, and transmit 24/7, so your Tellybox is totally wiped out?
My radio's are "too useful to live without" and cost way over an order of magnitude more that your "gadgets". Your PLT is illegal, my equipment is legal. PLT products do not comply with EMC Essential Requirements. It is inherent in the design. We have demonstrated that. Why do you think that Comtrend have not replied to El Reg? Why do you put your convenience over other peoples?
They know they are in the wrong. They claim to comply with specifications that they simply do not.
If my name was Harold Fitch, the chap that signed the Declaration of Conformity for the Comtrend DH10PF, my arse ring would be twittering now.
Just run a wire from Point A to Point B. Look it is pretty cheap to do (cost less then the BT Vision Kit!) and if you can't run the wires then TOO BAD!
When the complaints come from the Military Radio people when a terrorist attach happens, they MIGHT listen. We can only hope so.
Of course, the fallback position is two tin cans and a string. Works quite well. Could even be considered "wireless" (but not "stringless").
'Old men in tweed jackets'
When did radio amateurs get an image makeover?
Sorry to burst your bubble but the image most people have of hams is of a sweaty, fat, pipe smoking old man with a personal hygiene problem and NHS glasses held together with sticking plaster.
Of course there may be tweed involved but only because it was cheap at the local church fete jumble sale.
The Register 
Biting the hand that feeds IT
Copyright. All rights reserved © 1998–2024
