Powerline network radio interference debated in Commons Interference from PLT was debated in the UK Commons last night. At least an attempt was made to do so: the BIS minister preferred instead to ignore the questions and focus on the bearded minority. The matter was raised by Mark Lancaster, MP for Milton Keynes North, as an adjournment debate comprising a statement and response …
People not involved in radiocommunications often do not realise that just about all wireless/radio communications struggle with various forms of electrical noise. Wireless signals compete with every conceivable form of noise generated both by nature itself, lightening, solar disturbances, aurora borealis etc. as well as human-made electrical disturbances such as from motors, electrical switches, RF heating and other competing transmitting devices.
In addition to all that interference, radio circuits (paths) are incredibly lossy. The loss of signal from the transmitter to receiver can be (and usually is) enormous. Path loss figures of 120-140dB or more are not uncommon. Because of these huge losses, radio engineers are always concerned with how much margin there is between the received signal and the noise--so much so that the signal-to-noise ratio (expressed in dBs) for a given circuit bandwidth is essentially the most significant engineering parameter in wireless communications.
To illustrate the point, a powerful television transmitter can have a power output of between 100kW and 1MW yet the received signal at the typical TV set is so infinitesimally small that if amplified a thousandfold would probably not light the tiniest of pea lamps.
Keeping radiocommunications working efficiently is a remarkably complex and sophisticated engineering operation. Over the last 100 or so years since Marconi spanned the Atlantic, many complex rules have been formulated under the auspices of ITU (International Telecommunications Union) with the express purpose of optimizing and finely balancing competing demands for radio spectrum from various radio services. Interference and noise being one of the predominant concerns for the international regulation.
Into this mix comes PLT/PLC/BPL bulldozer. This broad-spectrum signal--which is better suited to modem-to-modem communications--pays no credence to the delicately balanced mix of incredibly minute radio signals contained within the specialized, especially-allotted radio frequency bands designed specifically to minimise interference. PLT just blankets the lot. To make matters worse, the PLT signal (which ought to be contained within a shielded cable to stop it radiating), is in fact connected to the world's biggest 'antenna'--the world's power grid.
Whilst regulators and PLT companies pay lip service to minimizing interference by tailoring the spectrum to work around some of the more susceptible wireless circuits, it is essentially tokenism. Whilst some radiocommunication circuits initially appear better off--usually only in specific areas--PLT is radiating everywhere--across cities, up into the ionosphere etc. In essence, PLT can be likened to a diffuse fog that's enveloped the radio spectrum across the whole planet, thus PLT is effectively increasing the noise floor with which existing services have to compete. It's interference pollution of the very worst kind. It's environmental damage to the radio spectrum on a level akin to or worse than the Alaskan Exxon Valdez oil spill disaster; yet except for small numbers of radio amateurs, few others complain.
Why this unmitigated disaster ever happened is still open to debate and a full analysis (but I briefly touched on a couple of issues earlier).
I've been following this argument with (vague) interest for a few years. It's certainly a tricky one. On the one hand the law is most certainly on the side of the Hams. On the other side, Home networking kit is vastly more useful and will continue to be sold regardless. I was trying to think of a parallel and the only one I could come up with was cars.
When cars first appeared all road-laws were (obviously) in favour of pedestrians, horses, carriages and (to a lesser extent) bicycles. However, it quickly became obvious that cars were vastly more useful and were going to take over road use no matter what our law makers did. Therefore they did the sensible thing and changed the law in favour of car drivers. Now, pedestrians, cyclists and horse riders are 2nd-class citizens (at best) on our roads. There is no moral justification for this. They were there first and are more vulnerable. Theoretically they should be protected from the car. But it made economic sense and, in any case, the law was changed to reflect the emerging reality.
Of course, I am not suggesting PLT is as important as the car but it is quite clearly vastly more useful in terms of both public uptake and economic driver than using the spectrum for amateur radio hams. It is not morally right and hams can rightly feel aggrieved but we are (moving toward) a post-Christian society where economic reality sometimes comes ahead of moral "correctness".
(and please don't start with the "what about the military?" argument. If it was truly interfering with military use it would have been stopped in it's tracks)
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PLT is so fundamentally flawed that it's only seen the light of day because of carpetbaggers and charlatans, the incompetence of regulators and blind eyes of standards bodies.
There are much better engineering solutions which keep the spectrum 'green' and pollution free.
"If it was truly interfering with military use it would have been stopped in it's tracks"
Once this may have been so, but it's not the case anymore. Shame I've not the time or space to debunk this statement.
Suggest you do some research, begin with the NATO doc ($$TR-IST-050-ALL.pdf)
Even if there was some official conclusion that ham radio was unimportant, and it could be shown that nothing else was affected, and it was concluded that PLT equipment was important enough to deserve lax regulation, the powers that be should still at least be honest enough to come out and say that, and change the regulations rather than just carrying on as if nothing is happening.
By basically ignoring what's happening, they're effectively admitting that they *should* be doing something, but that they just don't find it convenient to do their jobs.
Whether that's down to simple idleness, excessive connections with lucrative industry, or anything else on the part of Ofcom +/or ministers, it's hardly a good example to set - '"There *are* rules, but we'll pretend they don't exist when it suits us".
Whatever the actual reasons for inaction may be, the *impression* they give is of incompetence or corruption.
And then politicians moan about how people are cynical about politics and politicians.
>>"It is not morally right and hams can rightly feel aggrieved but we are (moving toward) a post-Christian society where economic reality sometimes comes ahead of moral "correctness"."
And when British society was supposedly Christian, you think that morality always came ahead of economics?
It seems that you have no grasp of the subject, the problem is that there is no real way to keep the RF inside the cable. Consequently it will escape and affect other things. You will obviously understand that most aircraft will probably have to be grounded. During the 1970's a CB with only about 4 watts did that as his frequency multiplier due to poor SWR blocked both the landing frequency from then West Drayton and also all the emergency vehicles at London Airport.
You can imagine it :- Tango Charlie 13 take bzzzztatatatssszta roger. Useful!
As a former Elect tech for the USAF and radio op BFG and instructor radio for ATC and running my own business as an electrical contractor, let alone being a radio amateur I have a wee understanding of the rammifications. It will only be a brain dead who sanctions this again. Anyway, I thought that this was thrown out several years ago after tests revealed economically flawed problems.
Guess I will have to connect an RF transformer to the mains and crash out a CQ EDF.
A lot (most, if not all) of compact florescent lighting splatters right across the spectrum.
It could be that OfHalfWits decided that PLT was emitting less than CFL so it's ok, but in 5-6 years time CFL will mostly be dead (LED prices are in freefall) and PLT will still be around. :(
Some chipsets for PLT clearly use higher frequencies for speed gain whilst others do not. There are 2 main chipsets on the market that everyone is using to beat on PLT in general. The original kit supplied by the largest UK telecoms company for one, who are now using something different which should not cause the same issue.
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"All chipset, be they DS2 or the new VHF-based Gigle,"
You're missing Intellon - used by many/most of the HomePlug stuff. The notching is also configurable by firmware.
" cause un-acceptable radio interference when used over un-balanced mains wiring."
'cause radio interference' - the degree of acceptability is dependent on many more factors than the chipset and vanilla firmware in a PLT device.
PS. There's a hell of a lot of ACs around at the moment - any particular reason ?
"The original kit supplied by the largest UK telecoms company for one, who are now using something different which should not cause the same issue."
Are you really saying that because the largest UK telecoms company is a supplier that it has no vested interest?
Surely, not?
Doesn't everybody make rewiring the house with CAT5e/6 a priority as soon as they move in?
I, for one, welcome the opportunity to drill holes through walls, and drag cables through buried hosepipes, and crawl through insulation-filled dusty loft spaces, and risk life and limb on dodgy rafters in the name of establishing a reliable network connection between one side of the house and the other.
I find the experience of appearing on Google's wifi database disturbing. And broadcasting my network traffic several blocks via powerlines is unappealing too. (Granted it's encrypted, but how long will the algorithm remain publicly unbroken?)
Shielded cabling for me, thank you very much. I like my signals crisp and guarded.
"can't be done cleanly" is shorthand for will not be practical technically or economically in an environment where legacy-designed mains cabling is in use, ie 99.99%+ of all premises in existence.
Legally speaking, vendors should be able to provide demonstrations that their product will meet CE requirements in a realistic environment. It's not supposed to be down to objectors to show where the product fails the requirements.
Anyway, you say it can in principle be done. I say it's unrealistic,
I say if recabling is required to ensure CE compliance of PLT kit, why not put in proper LAN cables at the same time so that there is zero risk of PLT-related emissions? (Because the PLT business model disappears, that's why, obviously)
Happier with the new form of words now Tim? The net effect is the same, PLT can't be done cleanly in the real world in any practical sense.
'"can't be done cleanly" is shorthand for will not be practical technically or economically'
If i'd known that convention, i'd not have said a word.
"Legally speaking, vendors should be able to provide demonstrations that their product will meet CE requirements in a realistic environment. It's not supposed to be down to objectors to show where the product fails the requirements."
I agree
"Anyway, you say it can in principle be done. I say it's unrealistic,"
I also agree with both - there is no confict here.
"I say if recabling is required to ensure CE compliance of PLT kit, why not put in proper LAN cables at the same time so that there is zero risk of PLT-related emissions? (Because the PLT business model disappears, that's why, obviously)"
Yep - i've been saying for months.
"Happier with the new form of words now Tim? "
Yep - that was my whole objection. I just hate absolutism.
"The net effect is the same, PLT can't be done cleanly in the real world in any practical sense."
I agree with that too.
I wrote: you say it can in principle be done. I say it's unrealistic,
Tim wrote: I also agree with both - there is no confict here.
There is indeed no conflict, that's why I chose those words, but had neither time nor space to explain explicitly.
Anyway, we're agreed, as are most (all?) logical-thinking independent-minded people on this subject, as they have been since (e.g.) the RadioCommunication Agency's DSL/PLT/RF Technical Working Group(s) back in 2001.
But WTF can folk actually *do* about this? Please don't suggest "write to your MP", mine's a useless timewaster, and so are most of them.
off topic ps:
El Reg: Captain Cyborg is back! The recently invisible Kevin Warwick is on BBC Today as I type this.
As a radio ham I keep wondering what would happen if I lodged a complaint with OFCOM/BBC about PLT causing me as a ham interference......
If it was the other way round and I as a ham was causing interference it would potentially be investigated and I could be asked to stop for a period...
Do we think they will ask said PLT user to unplug for a period...
Or is it same old one rule for one etc....
...272 times. And with resolutions in 230 odd of those cases.
In most cases BT Vision installations are the culprit, and BT know that the Comtrends are problematic so they come round and remove them and hardwire with ethernet cable instead. However, Ofcom say they don't have the powers to compel this so if the BT Vision customer refuses the cabled approach then there is currently a stand-off.
A selection of interesting "articles".
The last is interesting.
http://stakeholders.ofcom.org.uk/binaries/enforcement/spectrum-enforcement/PLT/ERA-RFI.pdf
http://www.ofcom.org.uk/radiocomms/ifi/enforcement/plt/
http://stakeholders.ofcom.org.uk/binaries/research/technology-research/pltreport.pdf
That is indeed well worth reading.
Didn't the RSGB used to have spectrum defence fund or something? e.g.
http://www.rsgbshop.org/acatalog/Spectrum_Defence_Fund.html
Can any kind reader confirm whether it's still active?
I particularly liked the non technical (not to mention nonsensical) nature of "Ofcom has said that failure to meet a standard does not mean a product is non-compliant. "
When I were a lad, things that met relevant standards were known as "compliant", and things that didn't, weren't.
Obviously I'm behind the times. But in an era when the IEE Newsletter could be mistaken for T3, maybe that's my problem. Does the IET even have a stated corporate position on the PLT subject, or are their folks at HQ just waiting for their next award for magazine layout+design?
Whose name is on Comtrend's published Declaration of Conformity? If these named individuals, rather than their corporate employers, had to be individually accountable for their actions (y'know, "lie to us and we lock you up", kind of thing) would these things work out any different?
Thank you, have a good weekend.
http://www.rsgbshop.org/acatalog/Spectrum_Defence_Fund.html
Many of us "amateurs" are also proffesionals. If we were for example lorry drivers, does making us being on motorcycles make us amateur drivers, does driving an ambulance for a living but driving a car at weekend make you a weekend driver.. To feel enthusiastic about ones chosen proffesion enough to also dabble in its various forms does not make us amateurs.
Possibly in these days the name is a misnomer, however, seeing as many of us also work within allied fields, or continue after retiring should really give us a better chance to convey to others the various situations.
Hence many of us may feel inclined to coment to the adverse anonymously to preclude potential situations as could develop.
If the so called investors were REALLY serious then they would look at Wimax, total removal of all phone lines, each person with a FREE phone in his location, really fast internet access and the like. CHEAPLY, say £20,000 1 time payout and virtually no running costs apart from electricity.
No cables.
Therefore it is in the interest of idiots like the MP who uttered the daft statement and other do gooders to take heed. There are sufficient lines (intended pun) of routing for the internet and telephone without recourse to dubious practices. The removal of all the copper wire precluding theft for scrap and replacing with Fibre will allow speeds up to silly speeds, let alone the reduction of exchanges and the like and interference from outside sources will be of major importance, so to spend vaste sums of money on aforesaid systems instead of the fibre is a course that will only be beaten for stupidity by the DAB system that has more holes than a collander and is now not being considered for the EU.
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