"Isn't this just a bunch of radio hams making a big noise about a dying hobby?" This was one comment pointed at me in a forum.

Radio Hams, who we should really call Radio Amateurs as per their official title, have certainly been vocal about the issue - there can be no mistake. However in quantifiable terms, although some Amateurs have quite a hard time due to this technology, the greatest effect is being felt in the shortwave broadcast arena.

Knowing that the Amateurs would give them a hard time and in line with ITU recommendations, when the "Standard" was proposed for PLT, the Amateur bands were 'notched' out. This could be described as a kind of 'graphic equalizer' for radio in which certain ranges of frequencies are attenuated so as to reduce the likelihood of interference in that range. However, in the same way that different  Hi-Fi speakers will respond differently to tweaks on a graphic equalizer, so too do the PLT devices react differently to the various wiring systems employed in peoples' homes.

Staying with the analogies for a moment, for those old enough to remember when most, if not all car radios had telescopic aerials, if your aerial snapped off or was left partially retracted, you knew the range of your radio would be much reduced unless you were lucky enough to live or work right next to your radio station - you still see workmen today using coat hangers for aerials on their portable radios! With PLT something similar is happening with the electrical wiring of your home or office. The more there is, the better "aerial" it becomes to the PLT signals which are constantly leaking out. Since the frequencies used by the current generation of PLT are 2-30 MHz, any length of wire more than a couple of metres has the capacity to radiate a significant signal. How much wiring does your house have in it? Think about your sockets and lights and light switches for a moment. I'd bet you'll have 100 - 200 metres if it is a house and plenty more if it is an office complex.

This problem is exacerbated by a phenomena known as intermodulation which is caused by semiconductor devices found in common household appliances and dimmers. The "non-linear" devices as they are called, modify the PLT signals in such a way that the separate 'channels' become jumbled up creating new unwanted signals which cause even more interference than the "pure" PLT original. You could think of it like trying to listen to three songs simultaneously, all at a similar volume; not a pleasant prospect, eh?

In the end, the effect is clear to see by anyone who wishes to look. Of course, you might say "Stuff'-em" they are only ham radio freaks. I need my broadband moved around the house - and my BT Vision (IPTV), why should I care? The Wi-Fi is all jammed packed round here and don't work properly any more."

Well I'm not here to judge, just inform. Only you can decide which route is best for you. There are some facts which are pertinent to making an informed decision and I would be obliged if you would humour me a little longer.

The radio spectrum is a natural resource. We tend not to think of it this way since it's not a tangible substance which will run out one day, is it. -- -- Is it?? Well actually it is a finite resource. There is only so much information you can pack into a signal before that signal starts merging with another. The radio spectrum is full - overflowing actually. This is why to transmit almost anywhere requires a license - so the administrations of any country can control the use of the spectrum to prevent interference and maintain sufficient order and quality to receive a service.

EMC Engineers (the guys who make sure electronic devices don't interfere with each other)  have been warning about employing this technology since the 1990's. Now it is in mass production and one company, BT (British Telecom) are distributing PLT adapters with their "BT Vision" product. Although BT are not the only supplier they are by far the most expansive.  If Ofcom were to admit that the technology should never have been allowed into active service, who picks up the cost? For this reason Ofcom continue to claw at every hope that somehow they can 'prove' the technology falls within acceptable limits. We will look at this in another article.

Now to paint a picture. In this current era we as citizens have become acutely aware of the threat of terrorism. There's something about it in the news numerous times each week. Remember back to that fateful day in September 2001 when two jet airliners flew into the twin towers of the World Trade Centre? What is not commonly known about this event (but is easily verified) is that when the towers collapsed, they took with them considerable mobile telephone infrastructure - three of the major phone companies had their transmission equipment and aerials on the North Tower and when this collapsed, the phone network crashed.

The Radio Amateur community mobilised and used their considerable knowledge, expertise but most importantly their radios to coordinate and support the many services which were overwhelmed. Indeed, this is not an isolated example - whenever and wherever there is a disaster, the Radio Amateurs are there to provide support and infrastructure when normal channels of communication beak down.

What if they couldn't hear? What if the frequencies were all jammed up with interference? This has happened. In Linz, Austria in 2007 a disaster relief exercise was rendered useless by PLT interference. It is fortunate this was an exercise and not a genuine emergency. Imagine for a moment if it was your wife, girlfriend, mother, father, brother, sister, husband, son or daughter who's very life depended on getting that message out? Ofcom, the UK communications regulator states in their September 2009 bulletin that "...there does not at present appear to be any significant public harm arising from this  situation...". Quite so, not yet.

This of course belittles the countless thousands of users around the country who can no longer hear their favourite radio channel, or who's enjoyment has been decimated by the invasive interference which PLT inevitably causes. It pays no heed to the persistently growing population of migrant workers who may well rely on Shortwave broadcasts to keep up to date with the daily events of their home country. At the time of writing, the number of complaints reported on the Ofcom website is a long way from being accurate - a recent Freedom of Information Act request has determined this much. Indeed, PLT is currently now in pole-position with regard to the number of complaints received by Ofcom's interference team - and it is rising quickly.

In September 2009, in the same bulletin Ofcom concluded "no significant public harm", they also announced that due to Stakeholders' concerns regarding PLT, Ofcom had commissioned a report into the potential effects of the technology. If Ofcom were so certain that there is no issue with the technology, why commission a report at all? They are, after all, the experts, no? Well it seems not and this point will be further explored in the coming articles.

In the next article we will look at some of the more technical aspects but try to keep the jargon to a minimum in an effort to unlock the mysterious world of Electromagnetic Compatibility legislation and the shocking truth about the validity of the CE label the PLT devices sport.

This issue has so concerned the top Electromagnetic Compatibility experts that on August 27th 2009, a number of leading experts and organisations met in London to discuss the non-compliance of products with the EMC Directive, and in particular issues associated with ‘Greedy PLT’ - they decided the solution was...

 to ban it. . .