Does powerline networking nuke radio hams?

Paul Ockenden Read more October 7, 2009

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.

Does powerline networking nuke radio hams?

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.

On the one hand you could argue that amateur radio is a long-established hobby, which the upstart powerline networking technology is beginning to wreck, where the adverse effects are almost certain to become worse in the future. That’s a compelling argument and it obviously raises strong passions among the radio enthusiast camp. I even found one website that declared these devices were a breach of Article 19 of the Universal Declaration of Human Rights (see Right stuff).

On the other hand, you could argue that the world has moved on, that shortwave radio is a “legacy” hobby while IP-based communication is very much tomorrow’s technology, with powerline networking forming an important part of this new world.

I didn’t experience anything to get all green ink and CAPITALS about
Indeed, most, if not all, of the shortwave broadcast stations being blocked by un-notched HomePlug frequencies would be available (in much better quality, and not subject to atmospheric conditions) via internet streaming. You could also argue that there are far more potential users for HomePlug devices than there are radio amateurs, so that in terms of sheer numbers the networkers would seem to have the advantage.

Having said all that, this is the Real World Computing section, so I need to get beyond the current heated online argument and find out what the effect actually is in the real world. So I got out my trusty shortwave radio (a lovely little Sony ICF-SW100) and, sure enough, within my house I heard lots of RF noise from my HomePlug AV kit. What was noticeable, though, was that the worst of this noise happened only during data transfer, so web surfing and checking email just caused the occasional burble, whereas copying gigabytes of data across the network really made the radio scream.

The other thing I noticed was that this interference spans a wide band, and the notches I mentioned above are really noticeable; within one of those notched bands I have to get very close to my ring-main before the HomePlug interference will swamp the normal shortwave squawky voices and Morse code. Outside the notched bands, the noise from the HomePlugs is far more noticeable around the house – strong stations are fine, but the weaker ones are swamped by the digital drumming. I tried setting off a huge file transfer to max out the HomePlug interference, and then went on a walkabout. I didn’t go very far – just to the bottom of my garden (approximately 100ft from the house) – and from there I could detect no interference at all.

I appreciate that many radio amateurs will use more sensitive kit than my little Sony, and I know that some other people’s ring mains may act as more efficient transmitters than mine, but even so, after the venom I’d seen spilled online and via email I was expecting far, far worse. I didn’t experience anything to get all green ink and CAPITALS about.

So am I going to stop recommending HomePlug kit to readers of this column? Well, despite trying to present a balanced view here, I expect I’m in for another bombardment of emails because my answer is “no”. I still think that HomePlug devices are a boon to anyone working in an environment where Wi-Fi is tricky or unreliable, but from now on I think I’ll add a caveat to my recommendation.

The chances are you’ll know whether you have a radio amateur living close to you – they’ll have a socking great aerial strapped to their chimney or in their garden – and if you do have one of these enthusiasts living nearby, my advice would be to avoid HomePlug or other powerline networking devices if you can (or at least check with said neighbour to see whether interference from your devices is causing them any problems). After all, it isn’t worth upsetting the neighbours just to get an internet connection in your shed.

Likewise, if you have a radio ham living nearby whose equipment is causing problems with your TV reception, I’m equally sure that they’ll be happy to work with you to alleviate the problem. Hopefully, then we can all enjoy our hobbies in peace.