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Comment by tlrobinson | Hacker News Reader

Even better: some crazy Russian/Ukrainian kids listening to the local radio station through weeds (and occasionally getting some minor RF burns): https://www.youtube.com/watch?v=82s5Q3GIO9I

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It's abandoned radio station in Brovary, Ukraine, I've been there several times. There were two antennas — 180 m and 270 m with 100 and 150 kwt transmitters (later up to 250 kwt). Until 1988 they were used for radio jamming (BBC, Voice of America, Deutsche Welle), later for radio broadcasting [1]

AFAIK you could get serious burns [2][3] even when antenna was not powered any more. In this case it works just like huge receiving antenna, getting kilowatts of RF energy directly from atmosphere. Before the thunderstorm ropes holding the antenna literally glowed due to corona discharge effect.

A few years ago both antennas were demolished [4][5]

[1] http://vk.cc/4LQeGa (wiki, Ukrainian)

[2] http://io.ua/20405915p

[3] http://io.ua/20405932p

[4] https://www.youtube.com/watch?v=j6NgzzFrCv4

[5] https://www.youtube.com/watch?v=Pn6sLpDS0Ks

Regarding "AFAIK you could get serious burns [2][3] even when antenna was not powered any more", does it mean I can get "free" electricity from "thin air"? Did someone try this already?

You sure can. The normal fair weather voltage gradient in the atmosphere is around 100V per metre. When there are close thunderstorms this increases. Unfortunately for energy collection air is quite insulative. That's also fortunate in that we don't get shocks all the time just from standing around in an environment where your head is 200V different than your feet.

Popular Science once ran an article that showed how to build an electrostatic motor that ran off the atmospheric electricity you could get with something like a wire used as a kite string.

* https://en.wikipedia.org/wiki/Atmospheric_electricity

What's required for a tower to become electrified from the air? I feel like I've played on other metal towers in my life that were inert...

Most tall towers are aggressively grounded. You would need a tower insulated from the ground. A tower used as an element for a low frequency antenna for instance. I strongly suspect that those large black interlocking rings are used as a spark gap for lightning protection in the absence of a solid ground.

Once you were on the tower you wouldn't notice anything. You would have to get between the ungrounded tower and ground.

The interlocking rings are an Austin Transformer [1]. It's the only way to feed electricity to the aircraft warning beacons on the tower without frying the power supply for the light bulbs.

[1] https://en.wikipedia.org/wiki/Austin_transformer

There are a few "art installations" where people put fluorescent tubes under power lines.

https://www.youtube.com/watch?v=cXhZvyGtMrk

http://www.richardbox.com/press.htm

If I lived close enough I'd be trying to work out some kind of trickle charger for phones.

I don't think I'd want even minor RF burns - nasty nasty stuff.

What makes it worse than just a burn or a burn due to an electrical shock?

I can't find the reference but a ham operator once told me they can be imperceptible while they're happening.

Normal burns are usually localized to the surface of your skin. RF burns conduct all the way through your tissue, heating from the inside. It's a much deeper, more painful burn that takes an abnormally long time to heal.

(Or so I'm told. So far I've been able to avoid experiencing one myself.)

Unfortunately I wasn't able to avoid the experience, I hit the screw on a silver trimmer in an end stage while looking at another one. Nasty little burn with dead tissue in the center and living tissue all around it. 35 years later it is still there, I don't expect that it will ever properly heal, it's a dead bit in the middle of a living finger.

Yep, I have a RF burns on 2 of my finger tips that I sustained between 5 and 10 years ago... They are dead little bits of flesh. Discolored a deep yellow, there is no feeling left and they feel, I guess I'd describe it as, quasi-numb when touched.

I was an embedded engineer at an RF company and it sort of comes with the territory. We had technicians who had lasted 4+ decades in RF (same company, actually) with scars to show for it. Same story, mostly on their fingers from accidentally hitting hot spots.

What was the power level? We do a lot of RF stuff here and it would be good to know that we're safe.

I got mine at about 100W from a Tronser trimmer.

It really depends on a lot of different factors. Single-digit Watt levels can burn you under the right conditions, though obviously it wouldn't be as severe as at higher power levels.

I was burned by ~300W in the specific cases I mentioned. I think it probably classifies as second-degree burns and (because I was young and dumb) I never did anything to help prevent scarring or heal the tissue besides basic first-aid. Safety first, everything else is secondary.

You mean they conduct from the entry-point to ground, similar to a lightning strike or electrical burn? Or is this more like a radiation burn?

Actually, now that I think about it, it'd actually be most similar to how a microwave heats meat, wouldn't it? Microwaves being within the RF part of the EM spectrum and all. (Though not quite the same, given the lack of dipole interaction with water molecules outside of the particular part of the spectrum microwaves sit on.)

That reminds me of an urban legend regarding microwaves, which doesn't seem entirely infeasible. It involves a man working at a small fast food stand, who worked next to his microwave. Now his microwave was used often, and it had a small hole in the metal screen allowing microwave radiation to leak out. The man slowly starts to feel abdominal pains after a while, goes to his doctor, who diagnoses it as liver problems and recommends drinking less. A couple of months later, the man has died, and the autopsy reveals that parts of his liver were cooked.

I was told this story by my grandmother to prevent me from watching food cook in the microwave. That and cataracts, which can also be caused by heating up things that shouldn't be heated.

There is also the story of Anatoli Bugorski. He was debugging the worlds most powerful particle accelerator when he managed to look into the beam: http://www.strangerdimensions.com/2014/01/13/anatoli-bugorsk...

And he’s become part of popular culture due to the annual satirical year in review panel at the C3 congress giving out the fictional "Anatoli Bugorski Award for applied nuclear safety".

That doesn't sound very feasible. Microwaves work by standing waves, the magnetron doesn't just cook things when outside the oven.

I thought they worked by dielectric heating? Making polar molecules get all frantic and stuff. There is a safety mechanism to shut off the magnetron when the door is opened, and a screen to make the viewing window opaque to microwave radiation, but those can malfunction.

[0][https://en.wikipedia.org/wiki/Microwave#Effects_on_health] [1][https://en.wikipedia.org/wiki/Microwave_burn]

As far as I know, that's the mechanism by which microwave radiation heats molecules, but the specific design of the oven is to produce standing waves so microwaves can become concentrated. I may be wrong, though.

Not wrong -- the safety screen is part of the cavity resonator. But if there's a hole in it, or if you defeat the door interlock, you can still cook yourself with microwaves. In general I'm not too concerned that I'm going to cook my eyeballs by looking at my spaghetti to make sure that it's not exploding all over the inside of the microwave.

Going back to the "discovery" of microwaves for cooking food, the story I heard was a radar tech noticed a chocolate bar melted in his shirt pocket.

Here is a video explaining: https://www.youtube.com/watch?v=7FhwTelc5Tg

The turntable in my microwave failed when I heated up a frozen pizza, and the result was part of it was burned, and part of it was still frozen.

https://en.wikipedia.org/wiki/Microwave_burn#Injury_cases

Disclaimer: I am not a doctor or burn expert of any sort. I am an extra class ham. An RF burn will penetrate more deeply than a "conventional" burn of similar degree, possibly burning nerve cells, circulatory and other structures that an external burn would not. RF burns typically heal very slowly.

I can't compare RF burns to burns caused by electrical current, except to say that electrical current will follow some path of least resistance while RF energy will heat flesh in a pattern corresponding to the field of the radiator and the impedance of the whatever matter absorbs it, so these types of burns will have different patterns.

Also, RF energy is more damaging to tissues that lack blood flow to control heat. Like eyeballs, and testicles.

Right, but for that to happen you'd have to stick your... uh... various balls directly into the path of the RF field. Like at the business end of a big RF horn antenna.

The skin effect should result in a high-frequency AC current propagating at lower tissue depths than a lower-frequency AC current. Why would RF AC propagating in flesh not follow this general rule?

We're getting beyond my depth here, but a few things occur to me. First, I know microwaves `work'; the optimal frequency at which water exhibits the skin effect is about 10GHz, so at 2.45GHz the energy from a microwave oven penetrates meat effectively instead of only frying the surface, as one would expect if the skin effect dominated. Also, I suspect the skin effect could actually cause internal burns; an internal organ that exhibits a strong skin effect at some frequency will cause localized heating on its surface, burning tissue internally.

It's basically like putting your hand inside a microwave oven

Wait, is that thing just lightly fenced and casually has this much current flowing through it? Isn't that basically a death trap?

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