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Analysis 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 capped at 30 minutes. In his statement, Mr Lancaster pointed out that the BBC, CAA and NATO have all raised concerns about PLT - as have some at secret listening agency GCHQ - and that Ofcom isn't doing its job. In response, Minister for Business Mark Prisk retorted that the GCHQ document was never authorised and all the complaints to Ofcom come from "hobby radio amateurs", which proves they aren't important.

The GCHQ document is something of a red herring here: it was never formally approved by the organisation and while we have seen different versions (contradicting the assertion that there was only ever one draft circulated), it is certainly not the official position of GCHQ. The fact that someone with the job title of "spectrum manager" is concerned about rising levels of radio interference shouldn't come as any great surprise.

And let's be clear: powerline networking kit does generate huge amounts of interference in the short-and-medium-wave frequencies. High-speed kit gets up into the bands used by FM and DAB, with the amount of interference being dependent on the house in which it is used. These facts are not disputed. The question is if it matters, and if anything should (and could) be done about it.

The minister's other point was that the complaints all come from bearded* radio hams which "suggests the problem is confined". He also reiterated an argument we've heard before: that the number of complaints received by Ofcom has declined over the last few years, so we shouldn't be concerned. Of course, Ofcom stopped taking complaints about consumer radio within the last few years; those go direct to the BBC these days, and one can't help thinking that might have contributed to the decline in the Ofcom figures.

As for the radio hams: the question is if they are the only ones affected, or are they the only ones who know enough to complain (and to whom such complaints should be addressed). As we've said before, most people will just move their radio if it stops working, not call up the BBC or drop round to the neighbours to see if they've got PLT kit installed.

The amount of interference generated is entirely dependent on the wiring (and thus the antenna) to which the PLT kit is connected. If all your wiring runs though metal ducts, then you'll probably not see much interference, but in the wrong house the interference can be detected several blocks away, which is why proper testing and standards rather than anecdotal evidence is needed.

As for the concerns of the BBC, NATO, and the CAA, the minister unfortunately didn't have the time to address those. He did state that the CAA didn't approve of the GCHQ document, but that's hardly relevant when the CAA has confirmed its concerns to us before. You can see the debate in all its glory via the BBC, but don't expect anything dramatic as this is just one more round in the ongoing discussion of how much interference we'll tolerate for the sake of avoiding CAT-5 rewiring in our homes. ®

*He didn't say "bearded", but we felt it was implied.

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