back to article Documents show CAA fears over powerline networks

Both the BBC and the CAA are concerned that powerline networking will damage their services, though only one fears that it will lead to planes falling from the sky. Earlier this month the UK regulator Ofcom hosted a meeting on the subject, minutes of which have been seen by the Reg. At that meeting PA Consulting presented its …


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  2. Lou Gosselin


    Now when we're talking "powerline networking", I'm assuming we're talking wide area networks, and not consumer home lan. Is this right?

    Is this medium bi or unidirectional?

    The thing about power lines is that, before reaching the home, all current is inductively transfered through step down transformers. Any signal which is to survive that gap would have to survive the EM conversion before being used in the home. It's a little shocking that regulators don't have the authority to regulate this interference simply because it's not supposed to be radio equipment in the first place.

    The sooner we get end to end fiber, the better.

    1. Anonymous Coward

      Home networking

      It sounds like they are on about the home networking kit.

      The first paragraph states:

      "Power line telecommunications (PLT) apparatus uses a technology that can carry data on mains wiring around the house and is used to connect computers or other digital devices."

      The document also states "Over the past 12 months Ofcom has received 143 individual PLT interference complaints; all from radio enthusiasts"

      The document was last updated in September 2009.

    2. Anonymous Coward
      Anonymous Coward


      talking about the use of house wiring to carry high-data-rate signals around the house (replacing wireless lan) and also to carry services to/from the house via locally-installed interface (at the substation)

      Talking personally, one house down the road (300 metres)has the bt system...which gives me an "S" meter reading on the 80 metre hf band (3500 mhz) of S5 (+-). Effectively rendering that band useless.

      Such is life.

      What the CAA is talking about (one assumes) is an entire housing estate becoming a "transmitter" at the frequencies that ATC uses.

  3. Adam Salisbury

    Who sits on Ofcom's board then?

    Because I'll put money on it being somone from either BT or whoever's manufacturing their jerry built PLN gear (can you say Huawei?). And expecting the problem to magically dissapear; well what's the point of Ofcom regulating anything if that's their attitude to new technology.

    If it's causing significant interence now what about when it's densly deployed near hospitals and the like? I'm all for PLN inprinciple, but if it's not ready for prime time, outlaw all the kit and sue the shite out of whoever's flooding the market with rubbish they can't be bothered to test first.


  4. Andy Barker

    Powerline Networking = LAN, not WAN

    If you take a look at the YouTube video, you can see they are referring to those PowerLine / HomePlug type devices that route Ethernet over your home / office mains supply.

    Works a treat in the house i'm in, and has been much more reliable and cheaper than setting up WiFi.

  5. Anonymous Coward

    Could happen

    Aviation, being a rather conservative industry, is usually a century behind in its use of technology.

    Air to ground radio is VHF AM as are ILS and nav aids which also use phase reference techniques. They already suffer from ground interference so it's highly likely that nationwide signals added to power lines is a high risk.

    1. Naughtyhorse

      theres stupid then there's dumb then there's that post

      100 yr old tech?


      when did you last see an airliner covered in doped linen?

      valve radio sets? (okay pushing the 100 year thing a bit - say 2 beans tins on a string)

      rotary Internal combustion engines?

      of course its conservative, when it goes wrong people die 500 at a time, which never looks good in the press. But the tech is cutting edge.

      Issues about RFI, or even alternators in GA aircraft are driven by safety not some inherent luddite-ism.


      1. Anonymous Coward

        Ahhh an example of noise interference :o)

        VHF Aviation comms and navaids are pre WW2 developments. Get someone to do the math for you :o)

        Did you get the memo that the 20th century ended ten years ago?

        OVER. . . *CLICK*

        Feel free to make some more noise while I smirk behind my CAA commercial licence and instructor rating.

        1. Anonymous Coward

          Re: Mark_T

          Ok Mark, I'm going to bite here. And just to establish some credentials before I start, I'm an ex RAF Engineering Officer who used to be responsible for airfield aids. Firstly, yes the aviation industry still communicates using amplitude modulation over VHF (some of the time). There have been a bunch of advancements in this area though in the last 100 years. Miniaturisation through integrated circuits, better control of power output, improved aerials, better signal processing, etc. Navaids however have moved on a hell of a lot. ILS was first used to land a passenger aircraft in 38; however since then you have had major improvements to accuracy allowing the 150ft decision height of a class I ILs. The first fully automated landing using ILS occured in 64. Also in the 70s MLS (Microwave Landing System) was developed, this was largely ignored in the US primarily because of the arrival of GPS based systems which are now very popular; but MLS is currently being trialled at Heathrow so don't right it off.

          In general, through the Golden age of aviation in the post-war period, aviation led other industries. Many modern technologies in cars are off-shoots from aviation - for example anti-lock brakes.

          It is correct to say that aviation is conservative. It is polemic to claim that it relies on 100 year old technology.

          1. Sirius Lee

            Democracy in action then

            It seems the objection to the use of PLN - a great benefit to the general populace - is from a state broadcaster, an organisation which has failed to take advantage of any technological improvements in the last 50 years (and so far as I can tell haven't quanitified their objection) and 143 people who probably need to find something else to do in built up areas.

  6. PaulK

    PLAN or WiFi...

    Homeplug or buttplug.

    1. Scorchio!!

      Plugin networking

      Different sort of networking, different sort of packets, different sorts of virus. Hmm. How to share keys? Plug two devices in at the same time, press the share button for at least one second and no less than three? Three devices? Network clusters! Hmm, interesting possibilities here. ;-)

  7. Jason Bloomberg Silver badge

    Power lines

    The terminology is confusing as "power lines" are to most what is slung between pylons or buried under ground, the stuff inside houses is "mains". The article does mention "mains wiring" and "tower blocks" which should point to wiring and comms inside property.

    I'm not a Radio Ham but since the interference problems were noted - and PA have confirmed there are potentially serious problems - I have been recommending against installation of PLT equipment. Thankfully most equipment remains considerably expensive.

    If PLT messes up utility company's Smart Meters then I might change my recommendation. I imagine that will also be the catalyst to belatedly introduce legislation to cover the issue.

    1. Bill Ray (Written by Reg staff)

      Re: Power lines

      Sorry for any confusion - the subject under discussion here is networking kit that sends Ethernet connections over mains wiring in the home or office.

      This is generally known as PLN (Power Line Networking) or PLT (Power Line Telecommunications), the latter becoming more common recently.

      Broadband over Power Lines (BPL) magnifies this problem hugely, which is concerning as there seems to be more interest in the area lately.


  8. Matt 21


    I use this technology and haven't been able to detect any interference. It hasn't effected blue-tooth, wireless networks, radio reception (commercial frequencies), TV reception, cordless phones etc.

    What am I doing wrong?

    1. Peter Gathercole Silver badge


      You're not using HAM or SW radio, and I guess that you don't listen to the air control bands either. Have you checked MW or LW radio reception, which I always found prone to interference (you may still find these on steam powered radios, but a lot of radio's don't even receive them nowadays).

      There's LOTS of the EM spectrum in the radio bands, and radio, TV, Bluetooth and WiFi only use a very small fraction. Google (sorry, the URL is too long) for "Fuk_frequency_allocations_chart.pdf" (warning: PDF), and you will find a very interesting wall-chart of the spectrum use in the UK. Try to find the bands you use, and compare them to the whole.

      1. Scorchio!!


        I've tinied it down for you, because your search key included a redundant "F" that might fool others, and returned me no result other than this page: [Warning; PDF]

  9. David Austin

    Offcom: What Do They actually do?

    ...Because from where I sit here, they don't do a lot:

    misleading "Unlimited Broadband" adverts - pass it to the ASA

    Premium rate phone numbers - pass it to PhonepayPlus

    Mobile phone issues - Pass it to the Telecommunications Ombudsman

    Homeplug interference - pass it to..... we're not sure, but it's not us. Try the BBC. Or trading standards.

    Given that we have a government that is currently cutting redundant departments left, right, and centre, The above should have them a little worried...

  10. gerryg

    Oh how we laughed

    "A few radio hams" = a harmless group we can ignore because they aren't cool so although their hobby is being ruined by illegal RF generation, they've probably got beards, sandals and drink real ale and this is their punishment.

    Again the issue falls between two regulatory bodies so neither of them can do anything. All this accountability and nothing to account for.

    That being the case there's obviously some money saving opportunities to be found in the Autumn spending round.

  11. Trev16v


    I'm a radio amateur and CB user, and a few weeks ago I called on Ofcom to come and investigate interference I was experiencing from PLN. The chap came over and quickly traced it to a BT Vision installation a few houses away. Fortunately the householder is happy for BT to replace the PLN gear with a cable. So in my case I can happily use my gear for a little longer... until someone else nearby gets BT Vision.

    The amount of interference that these devices cause over the HF radio spectrum (30MHz and down) is just incredible, and potentially very damaging. Please don't assume it's just a bunch of nerdy radio anoraks like me who are going to have an issue with PLN; there are many, many other licensed services that use portions of the HF spectrum, including of course world broadcasts, marine, and aviation.

    PLN has come about because Ethernet cables and 2.4GHz wireless equipment are more expensive and time-consuming to install. This is why BT use them in thousands of BT Vision installations. But how on earth can we justify this cost saving at the expense of obliterating the HF radio spectrum and making it useless to other services? As PLN becomes more widespread, unfortunately that's just what's going to happen.

    Incredibly, these things have been allowed to go on sale without being subject to licensing or regulation because they're not 'considered' radio broadcast equipment. Unfortunately, electronic equipment obeys the laws of *physics*, not *bureaucracy*; if you're going to inject very strong broadband RF into the unbalanced tangle that is your house wiring, then presto - you have a bloody efficient and damaging HF wideband radio transmitter, end of story. (And no, the RF does *not* "stop at the fusebox", as some PLN manufacturers incredulously claim.)

    Ofcom says that the number of complains has declined recently. Hmm... could this 'decline' actually be more attributed to the fact that complaints regarding interference to SW broadcasts stations has now been offloaded onto the BBC? I'm glad I made my complaint anyway, and notched the statistic up by one!

    The article mentions the possibility of interference to ADSL. Going back to my case of PLN interference, I noticed that RF was being particularly strongly re-radiated from the BT line to my house (expected really, as we all have overhead lines from the same pole). I also saw that downstream margin reported by my ADSL router improved by about 1 or 2dB when the neighbour switched off the PLN equipment. Not very significant I know, but it demonstrated to me that even existing broadband equipment (which sits at the very low end of the HF spectrum) can be affected by PLN, too. This is why it's frustrating when I hear PLN users claim it's only a small group of radio anoraks that will be affected. RF works in mysterious ways, and all equipment such as your ADSL gear that uses RF has a level of susceptibility; and the more devices you have sitting in houses spewing out strong RF, the more you'll notice services and equipment that you enjoy and depend on being affected. Even if it's playing MW2 online!

  12. JaitcH

    Airport ATC frequencies are jammed by cable TV ...

    where the co-ax cable gets damaged and the centre core is exposed. See: < >.

    Maybe the CAA should check out air regulations and see if there is an answer there. Anyway, when the first 'incident' (crash) occurs people will wake up.

  13. NX1977

    security nightmare

    I can't believe pln is growing without addressing signal leakage.

    The last report I saw on this was regarding pln users being able to see data from other pln's upto a mile away!

  14. Anonymous Coward

    "possibility of interference to ADSL" - it's a certainty on VDSL!

    ADSL is medium wave radio down the phone lines.

    ADSL has a higher speed relative, VDSL (and derivatives), that is a worldwide standard using short wave radio frequencies down the phone lines.

    VDSL is currently being rolled out by BT in a small number of areas in the UK. BT's VDSL folks are desperately worried about the impact of powerline networking on the potential for widespread deployment of high speed DSL (BT don't want to think about widespread deployment of fibre to the premises). But without VDSL BT are without a high speed broadband offering to compete with cable and the niche FTTP companies (e.g. H2O, teehee).

    Unfortunately BT's VDSL people aren't allowed to say much, especially in public, because the main UK supporters of powerline home networking are.... wait for it... BT, with its BT Vision product.

    BT Vision is allegedly closer to making more money for BT than VDSL is, therefore BT HQ backs BT Vision rather than backing spectrum preservation, not just for VDSL but for anything else that might one day want to use the spectrum that PLN will make unavailable while PLN lasts.


  15. Nige_C

    Regarding PLT (PLN)

    So that there is no ambiguity, particularly aimed at the first few comments, the article refers to powerline network adapters, of the likes supplied by BT with its BT Vision broadband TV package and commercially available from most electrical retailers, which are effectively modems which use the internal electrical mains supply wiring of a building.

    I would also like to comment that I was one of the delegates invited to and participated in the meeting at Ofcom to which the article refers and confirm that the article accurately sums up the the two hour meeting during which we were allowed 30 minutes to question PA Consulting and roughly 50 minutes to question Ofcom.

    Ofcom agreed the technical content of the report but stated that the report did not change Ofcom's regulatory position on PLT which remains in line with their September 2009 Statement and the June 2010 "addendum".

    Do not think for one moment that the article is sensationalist, some of the UK's most respected RF and EMC engineers were present at the Ofcom meeting and they did not hold back on their professional opinion as to the seriousness of allowing this technology to continue. The CAA made a protracted and valid input to the meeting in which they expressed a deep concern for the implications for the future if large numbers of the devices are put into service.

    The mitigation technique proposed by the PLT industry and heavily relied upon by PA Consulting in their report was studied prior to the meeting and determined that instead of being a power reduction scheme to reduce interference, it will in fact have the ability to increase the power level used by the modems by a further 15dB which, taking the UKAS accredited test results of the Comtrend devices used by BT in BT Vision, which are already 36dB above the EN55022 limit, adding a further 15dB to this will mean in reality that the emission level will be the same as 126 thousand barely-legal devices all plugged into the same socket and operating at the same time.

    I realise that the technology is convenient - I used it myself, once, until I realised the consequences of my actions. We must also remember that Ofcom, far from being an independent regulator are simply marionettes dancing to the tune being played by DG Enterprise, who were also present at the UK spectrum stakeholder meeting, despite being neither a UK spectrum stakeholder nor a UK organisation - but had the time to quote their "no barrier to free trade" mantra...

  16. Paul Widger

    Ofcom are a disgrace

    It will be interesting to see what CAAs lawyers and technical investigations reveal.

    It is interesting to recall what the Ofcom field engineer said to me in the early stages of this saga

    which began for me in Feb 2008.

    "If it was up to me I would have them banned"

    "We (Ofcom) are on a learning curve on Powerline Adaptors"

    " I am surprised how far these things are radiating"

    No doubt they would flatly deny having made such comments as they are now being obstructionis

    in their approach and appear to be trying to defend the indefensible,not wishing to upset BT Vision,

    the supplier of the greatest number of these adaptors,preferring to victimise the victims of the interference.

    Ofcom are of course controlled by DE/BIS who take the line that it must be good if someone is making money from it and will do their utmost to disregard the downside.

    They will have big problems if the latest generation of adaptors sell in large numbers as listeners

    to FM and DAB who get a weak or medium strength signal could have their reception ruined.

    No doubt Ofcom are busy working behind the scenes to persuade CAA and BBC (whose research

    department reported unfavourably on this flawed concept some years ago ) that there is not really

    a problem, this will be an attempt to hide their incompetence from scrutiny.

    Ofcom have been made to look very foolish at the recent meeting, sadly they are still Judge,Jury,

    Court of appeal and reference point for other goverment departments,MPs etc so their statements,

    even if a load of twaddle, carry weight.

  17. M0SNR

    PA Report and ineptitude.

    The PA report states that there is a serious EMC issue and the only solutions to eliminating EMC issues caused by PLT don't exist and have not been proven (smart notching and power control).

    How is a junk PLT device going to be sensitive enough to be able to detect a radio signal using the house wirng as an antenna, and then determine if it's AM, SSB or DRM? It's a joke! Is a crappy PLT supposed to be as sensitive as a £2k receiver. Either way, tuning across broadcast bands would just be a sea of PLT noise interjected with the occasional broadcast station which would not be a pleasant listening experience, either on Short Wave or FM.

    Most importantly, the PA report failed to take into account intermodulation effects, where deliberately notched-out spectrum by a PLT can be filled by the PLT's emissions impinging on other mains equipment, primarily Switching PSU's.

    The limited amount of testing with a set of Belkin 1Gb devices that I conducted here demonstrated that the length of mains cabling between the PLT's altered the interference spectrum, which is quite understandable. Again, this has not been addressed by the PA report.

    The PA report is flawed and the investigation into the effects on VHF appear to have been rushed.

    I've yet to see a PLT reach anywhere near 1Gb and given Shannons Law, I'd love to see the spectrum that it would use to achieve it :)

    Ofcom say that they have no power? Remember this story?

    PLT DELIBERATELY uses CAA spectrum.


    Richard M0SNR

  18. Anonymous Coward
    Anonymous Coward

    Homeplug Interference

    Two questions

    1 Why do Ofcom have no notes from the meeting

    2 Why do BBC suggest to use homeplug units if they now know there is a problem

  19. Martin Usher

    The problem will be mitigated

    Its simple. PLN generates so much crap that people stop using the affected frequencies, thereby making the problem go away.

    Its a mystery how this technology was ever allowed to see the light of day. If this was a generic west African country I'd suspect a good bit of dash changing hands (but I suppose that sort of thing doesn't happen in England, does it?).

    1. M0SNR

      no idea

      @Martin Usher

      I really don't understand - apart from distribution sales (and I get the impression that margins are low) there is no money for Europe apart from Ofcom making money for interference complaints!

      As a commercial engineer, working in the real world, I cannot see any reason for PLT being allowed on the market. I might get a pair, up the clock so that they are running on a TV MUX and bollocks to any complaints (I know it wouldn't work but it's a dream)

  20. This post has been deleted by its author

    1. M0SNR

      two wrongs...

      Do wtf on CB, but when you guys start encroaching on 28MHz, you are taking the piss.

      You want to use Amateur frequencies, get a license. It's not hard any more.


      Richard M0SNR

  21. TkH11


    The suggestion that the authorities can't do anything to prevent this technology being taken because the law doesn't cover it and OFCOM don't have the necessary powers is I think false.

    It will be covered by European Directives to do with electromagnetic compatibility, the CE marking. Which basically state that devices must not interfere too much with other devices.

    If aviation communication problems arise, anyone who thinks that existing powers can't or that new powers won't rapidly be put in place to deal with it is living in cloud cuckoo land.

    Safety will come first. If that means banning the sale of PLN equipment, or making it a criminal offense to use it within say 10 miles of an airport, trust me, if there's a risk of an airliner crashing because the pilot didn't hear instructions from the control tower correctly, then this issue will be dealt with by the government very rapidly. So I wouldn't worry.

  22. Martin 71 Silver badge

    It's also covered by existing legislation.

    Just because it's not INTENDED to broadcast, doesn't mean that it doesn't require a license when it DOES. Or if it does mean that, the law is ****ed and we need a change.

    PLN/PLT/whatever is just laziness. Cat5 is not expensive, cat6 isn't even expensive these days!

  23. Anonymous Coward

    if there's a risk of an airliner crashing"

    "if there's a risk of an airliner crashing because the pilot didn't hear instructions from the control tower correctly ..."

    Your trust in the regulators is heartwarming but may be undeserved. According to some folks I know in the industry, it's only a matter of time before regulatory laxness (giving the CAA and their successors EASA the benefit of the doubt, some would call it incompetence) leads to big big trouble. gcc/gnat is perfectly safe for safety-critical code, right?

    Things will happen *after* the accident. After all, the great and the good in the regulators thought the chances of two of three Pitot tubes failing identically at the same time were negligible. Then when it did happen a couple of years ago on flight AF447 (look it up), the "two of three" majority were trusted, even though they were the broken ones. Over two hundred people died as a result of that regulatory policy.

    I realise a lot more people die on the roads. Not sure whether it's relevant here though.

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