Regular readers will know that I’ve written several times over the past few months about powerline networking – that is, running part of your home or office data network over your mains electricity wiring.

In particular, I’ve written about the success I’ve had with HomePlug kit (both the older HomePlug 1 devices and also the newer HomePlug AV standard), and how I’ve become a great fan of this technology. However several readers have emailed to castigate me for recommending these powerline networking products.

These emails spanned the full spectrum from sensible and rational through to green ink and CAPITALS, but what they all had in common was that they came from radio amateurs, or people with an interest in shortwave radio. They claim that HomePlug kit affects their hobby in much the same way that urban lighting affects amateur astronomers, but rather than causing light pollution it seems that powerline networking causes radio pollution in the HF band (otherwise known as shortwave).

To make matters worse, this RF pollution apparently isn’t restricted to a particular narrow broadcast band; in order to get maximum range and throughput, these devices splatter bits across a wide range of frequencies. At least these were the claims I saw from readers’ emails.

A number of YouTube videos demonstrated HomePlug devices that killed shortwave radio reception

After extensive Googling I found lots of forum and blog posts from shortwave radio enthusiasts complaining about these mains networking devices, with certain factions of the Radio Society of Great Britain (RSGB) also singing from the same hymn sheet (although I did find the document which claims that for most shortwave users with a good setup, the effects should be marginal). I also found a number of videos on YouTube that demonstrated HomePlug devices that completely killed shortwave radio reception.

Lack of complaints

I was somewhat confused, though, because despite finding lots of protests, I struggled to find many complaints from people who’d suffered these kinds of problems because of their neighbours’ powerline networking. In most cases, interference was reported by people who had installed devices in their own house and had found this to compromise their own shortwave radio reception. Maybe I was just using the wrong search terms.

Among other things that my Googling uncovered was that the HomePlug Alliance (the industry body that defines the HomePlug specifications and certifies the various devices) had worked with the American Radio Relay League (ARRL), which is essentially the US counterpart of the UK’s RSGB, to “notch out” the most commonly used ham radio bands from the HomePlug spec.

As a result, it would seem that, unlike in the UK, the US radio community is reasonably happy with HomePlug, but less so with other mains-borne data technologies, particularly those delivering broadband-over-power-lines (BPL) to the home or office, which tend not to have the amateur bands notched out. These technologies aren’t really being much used in the UK at the moment, apart from in a few trials.

It seems the notches cover only the bands that radio amateurs use to talk to each other, not those used by long-distance broadcasting stations, so even the ARRL-approved HomePlug devices are causing concern to some enthusiasts.

Another thing that Googling revealed was a handful of forum posts where people were complaining about interference from, rather than to, radio enthusiasts. Apparently, if the person next door pumps out 1.5KW of HF radio waves, they can cause havoc with stuff such as TV reception and baby monitors. It seems as though this can be a problem even where the guy next door (and it nearly always is a guy) has a perfectly legal and properly adjusted radio transmitter.

It would appear that, at least from a technical point of view, there are valid arguments on both sides, but even if you ignore these technology arguments, the debate still doesn’t have any clear winner.