A recent thread about magnets wanted to know if you would feel any effects from a large magnet, perhaps similar to being close to a 500 watt antenna. Other posters described this as unpleasant and similar to being zapped by a microwave. This didn’t make a lot of sense to me unless you were talking about a microwave antenna. Also, I was under the impression that microwaves had to be of a particular frequency to have their heating effect manifest itself. Would you be effected by being close to, say, a 100,000W radio antenna broadcasting Metallica on 100MHz FM? Would the antenna arc if you were close to it? Does the metal get really hot due to resistance? Or can the 3 meter waves somehow affect you?
I wouldn’t want to get close enough to an antenna being fed with 100,000 watts to find out if it gets warm or not. This wiki article on antennas gives some insight on the factors that can heat up an antenna, such as its ohmic resistance, efficiency and reactance.
ETA: The FCC has produced a document that’s worth looking at if you want more information on all of this: (38 page PDF)Questions and Answers about Biological Effects and Potential Hazards of Radiofrequency Electromagnetic Fields
Any radio energy has the capacity to heat tissue. Any passing RF which doesn’t reflect off you or pass through you is absorbed and converted to heat. In general, the amount of energy that is absorbed increases with increasing frequency but there is no specific one which is “tuned” for maximum heating. Consumer microwave ovens operate at 2450 MHz; this frequency was chosen because at the time it wouldn’t interfere with any other devices and because it was low enough to penetrate well into most foods without being very strongly absorbed at the surface (and therefor not heating the inside well.)
There was a guy out here a few years back who was pulling out of the custom-vehicle shop lot with his brand-new conversion van that was rigged to be some sort of mobile DJ/audiophile setup. As such, it was packed with fancy amps, mixing boards, huge speakers, etc, costing quite a pretty penny. At any rate, as he pulled into traffic he was t-boned by some dude who was talking on a cell phone. Neither person was hurt, but the rear of the van was totalled along with all the guy’s electronics. The van driver flipped out, snapped the antenna off his van, and started whipping the other guy with it. He caught the cell-phone guy across the throat a few times, and the cell-phone guy started to choke and died at the scene.
The cell-phone guy’s family was further incensed when the cause of death was listed as “van-aerial disease.”
Back in my radio days, I knew engineers who got burns from touching antenna or transmitter components. These were not “hot to the touch” but real microwave type burns.
Don’t forget also that we’re talking about modulated RF waves: i.e. they contain information. Also don’t forget that natural, unmodulated, radio waves are also bombarding us, and always have been.
Some time ago I saw a documentary about base jumping (parachuting from a structure or geographic high point). One of the jumping sites was a very tall radio mast somewhere, I think, in Australia. They said that they where limited to something around 10 minutes at the top to avoid burns from the transmitter, they made comments about how they could feel the heat in their bodies.
But a powerful antenna won’t electrocute you will it? Also, isn’t frequency what determines is a wave will pass through you or reflect off you or be absorbed? Can a high power megameter wave zap you?
Anecdotal it may be, but I can testify firsthand that you can cook hot dogs by putting them on very long sticks and holding them in front of the microwave antenna of the local NBC affiliate.
I can also testify secondhand, having seen the evidence, that however sure you are that four people who work there are lying to you that the above is possible, it is still not a good idea to climb up and place your hand directly in front of same to test your theory.
Is there any truth to the fact that there is a relationship between the wavelength of the RF signals in a microwave oven and the size of a water molecule?
I was told this relationship was what allowed the oven to heat the food but not the plate / bowl etc.
I will corroborate that. When in the military, I worked on a secure world-wide microwave communication network and we regularly heated our lunches in front of the antennas during function tests.
The water molecule behaves like a tiny bar magnet. The oscillating electromagnetic field in the microwave oven causes the water molecule to flip back and forth, transferring energy to the food.
My father worked for the phone company up in Alaska, and he always told stories about guys who got burned from radio antennas, including one guy who got himself killed.
I remember a Mythbusters episode where they tested this. Their finding tended to disagre with your anecdotal info. They tested it by putting a turkey in front of a microwave relay antenna (as well as a large scale ships radar)…their conclusions were that there was no effect on the bird, even when it was put directly in the path.
Saw this episode. Not only is a turkey not a hotdog, but a newstruck dish isn’t a station dish. That tower they tried (and failed) to gain access to would’ve been a more reasonable comparison.
Well, if you saw it then you know that the station engineer stated it would have no effect…that the truck dish actually puts out more focused power (which is why they tested it that way…well, that and the chick in the truck was kind of a biscuit AND let them do the test).
Feel free to argue the point all the live long day, but I’ve done it, and it works. As mentioned above, I’ve also seen the burns on the hand of the last guy who tried to prove us wrong about it. Mythbusters can say whatever they like, but I tend to believe things I’ve actually done over statements from pseudoscientific television programs.
If you ever make it over to the Great South East, stop on by and I’ll prove it firsthand; I still have some contacts at the station. The hot dogs are on me.