Could Broadband Over Power Lines be Dangerous?

falconfighter writes " Broadband over Powerlines, once touted as the solution to many internet problems (developing 3rd world countries, etc.) has a new hazard. The system basically involves putting high amounts of modulated RF on a power line. The Amateur Radio Relay League has the most informative page on the topic. The hazards include exceeding MPE (maximum permissable exposure), RF burns, and disrupting the HF bands of radio. This last one would also work in reverse, meaning hams, airplanes, or the military keying up their radios could take out large areas of internet service (with airplanes, potentially over several hundred miles)."

First, and...

[Zondar]

Being near a hot unshielded antenna lead of sufficient power output is bad news...

Going both ways

[Anonymous Coward]

Do note that the problems of interference goes both ways: broadband over powerlines will jam HF communications (including emergency services some places). But at the same time a HF jammer or a HF over-the-horizon radar will jam broadband over powerlines.

HF being global means a jammer in the Pacific can take out broadband in Europe.

Lets hope someone takes a wise decision

[Eric S Rayrnond]

HF radio is *the* communication medium for many life-critical situations. It is the only affordable communication line for many NGOs operating in third world countries, and HF equipment is much easier to setup and more rubust than satellite equipment.

Until now, the HF spectrum has been carefully regulated to avoid harmful interference. It is just not acceptable to sacrifice it simply to get a cheaper Internet access. There are a good set of broadband technologies available which almost do not interfere with HF users.

Let's hope politicians don't wait to do anything until a true emergency happens...

Wonderful.... not

[Arimus]

Oh goody so now the power companies will have even more control as they blat out most LF/HF wireless within a certain distance of their transmission lines (or should that be antena lines now?)...

Not to mention won't people who choose not to receive broadband via power still be able to tap into the transmission signal and so monitor other peoples traffic easier than trying to splice into the fiber backbone (oh hang on.... wonder if the gov't might not be keen for this very reason)...

Aircraft ILS and power-line transmissions

[CdBee]

My grandfather was an air-crash investigator, and once investigated a european crash (May have been Switzerland in around 1970, apologies, I don't have any details) in which an airliner had apparently tried to land on the side of a mountain. It was proved that the accident happened due to the local electricity generating grid using high frequency modulation to carry messages over power lines. The chosen frequency was a close enough match to the Instrument Landing System on the aircraft to cause it to engage. I hope modern airliners have better ILS.....

Re:First, and...

[grub]

Being unshielded makes me wonder about the likelyhood of "sniffing" with a receiving antenna and amplifier. It's spread spectrum like the cable 'modems' but ya never know. I'm sure the NSA is ready for any potential rollout. :)

Solution?

[sameerdesai]

I know most of the big cities have their power lines underground (at least mine did). The broadband company took it to their challenge to even put the broadband cables underground. I guess that could provide sufficient shield along with the shielding on the cable itself. Now the question is cost of doing this over the entire country, which I have no clue. Again I am just curious as to how will these two cable interact because it is failing my general electromagnetic knowledge.

Don't use RF

[Hellkitten]

What some power companies here (norway) have done is to use a special kind of machine (it looks like a really clever invention) that "spins" fibre optic cable(s) around high voltage power lines. This doesn't work for buried power cables, ofcourse. This technique gives several advantages: Cheap, the cost is the cable and a helicopter, no digging, no new cable masts, no buying right of way. Security (I'd think twice before trying to mess with a cable wrapped around a high voltage line :D ). And since light won't be disturbed by the magnetic fields generated by the current there is no need to worry about power and data interfering with each other

There's no real need for it in the US either

[Sycraft-fu]

We really don't lack for communications infastructure. Between our huge telephone and cable networks, and growing amount of fibre thereof, we are doing fine. The majority of the problem with getting broadband to end users comes from stupidity and/or anti-competitive behaviour on the part of cable and phone companies, not lack of infastructure to carry the data. Maybe in developing nations there is more benefit, but I kind of doubt it.

Jury is still out on the danger.

[TEB]

The hazards of RF exposure are still being debated. Hazards from BPL would need years of study. That being said people are probably at more risk from intentional radiators like WiFi points. This is due to the way the body absorbs RF. The absorbtion is a function of the wavelength of the RF and the size of the human body. I don't remember the exact data but the shorter the wavelength the better the absorbtion. This does have some exceptions but I do remember a strong absorbtion around the 1Ghz range.
The interference problem is the greater of the two. Yes it will interfere with radio communications but the interference will be worse for BPL. Aircraft have the potential to cause interference over a wide area due to their altitude, but the tranmitter is relatively low power. The real problems will start when a ham operator can't talk to his buddy 20 miles away. They get tired of the interference so they kick in the linear amplifiers. Since the max leagal power for most of the bands is 1500 watts they have the potential to take out BPL in a very large area.

Re:Don't use RF

[carndearg]

And since light won't be disturbed by the magnetic fields generated by the current

I remember reading a very interesting article years ago, may have been 1980s, about a device for measuring leakage currents in metal pylons(towers) on very high voltage power transmission lines. It was a fibre optic device, you wrapped it round the base of the pylon and measured the amount of light you could transmit through it. It seems that the magenetic field generated by the leakage current affected the refractive index of the fibre, varying the amount of light that could escape, thus you could non-intrusively measure the current by measuring the amount of light you lost.

Of course, they probably used a special fibre optic material with the right properties, but I have often wondered how they get round this with the fibre-on-powerline systems. Sadly I cant find anything about it on the www.

Re:Laugh Test

[moonbender]

It's considered an option here in Germany, although DSL is now widely available and seemingly has basically killed demand for BPL. However take note that if I recall correctly it was considered a means to connect the "last mile" not in rural but in urban areas. Power lines suspended in the air are virtually unheard of in German cities as far as I know. The maximum length of data carrying wire was less than a few kilometres - I assume it ended at the nearest node in the electricity grid, similar to the way DSL does.

Re:Gross Disinformation

[bgelb]

I agree that MPE limits and RF burns should not be a problem. I'm not sure where the original poster got that from - I also don't see it on the ARRL site.

HOWEVER, the interference concern is VERY real. 250mW can go a long way - I'm not sure where you get your "few hundred meters" figure from. I know people who operate "QRP", a low-power mode, who regularly use similar power levels to talk to ham operators hundreds of miles away!

Let's not forget, a "transmission line" at 60 Hz is much more like an ANTENNA at HF! Powerlines will radiate VERY well.

What's so different about the interference from BPL is that its broadband - that is to say the signal is several tens of MHz wide, spanning all of the HF bands. A spur from another local noise source or unlicensed device is less of a problem because you can simply use another frequency - with BPL this is not possible.

Make no mistake, BPL poses a real problem to HF communication.

Re:Don't use RF

[nexthec]

Not quite what you are talking about, but NxtPhase [nxtphase.com] makes optical voltage and current transformers for measurment of high voltages lines using the Faraday effect. Quite cool, a grad student here at Uof I has told me he can make one for a couple of hundered ;->

Duh. But people don't want to hear it.

[Anonymous Coward]

It's a pleasure to see that this is getting coverage though. Especially at Slashdot, where the majority derides and censors this stuff down very quickly (see what happens on this post).

I've pointed this out in the past (it seems obvious). Also, the X10 stuff is probably an issue. I've had guys who monitor RF fields for a living tell me that X10 and alarm stuff is a lot worse than the nearby powerlines, because it's of the power levels and the fact that it's not a static field.

And god forbid we get into wireless, where the power output is worse than the Federal standards for emissions by microwave ovens (by about 100 times IIRC).

And no one has done any safety studies on this stuff. The closest is cellular; and those studies have raised questions.

People want their technology. They don't care about the consequences. Personally, I view it as Darwinian selection in action

Re:Neighborhood popularity of amateur radio

[sm0yby]

I read (think it was in Hints & Kinks 15, but I am not sure) about someone who put up a tower. Nothing else. A neighbor complained to the local authorities that it was interfering with broadcasts and someone came over to check it out. Turned out there were no antennas in the tower that could cause any interference. Duh. .... ..

From what I understand, someone also pulled the plug on BPL in Austria. BBC also made some measurements and concluded that it had the potential to seriously disrupt short wave radio broadcasting - so what wouldn't happen to the much weaker signals regularly used by amateurs as well as others (like air traffic, military or for emergency communications)?

..