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Old Mar 11, 2005, 8:11 PM   #1
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This might be a dumb question, but there's a particular outlook i'd like to get some shots from and it happens to be -right- next to an active radio tower. There's a warning sign by the tower saying something to the effect of 'Exceeds maximum output levels safe for general population'. I was curious if anyone knew if there would be any harmful signals that would possibly effect anything in the camera/memory. I'm using a Panasonic FZ-20 with a Kodak SD card. I've taken my cellphone up there with no ill effect, and seen trucks drive up there, so I wouldn't -think- that it would be an issue. But, better safe then sorry?
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Old Mar 11, 2005, 8:19 PM   #2
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Your camera will be fine.

You however may not. I am a Microwave Radio technician, and depending on the power of that antenna, it can be lethal to you. If you venture up there and start feeling sick or warmer than before, leave, immediately. Those are the first signs of RF radiation poisoning.
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Old Mar 11, 2005, 8:48 PM   #3
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Thanks alot, Rob, i'll definately be careful. I've been up to this particular tower and know of other people who have gone up too, so far with no ill effect, but i'm also not willing to get up next to the antenna since I saw those signs.
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Old Mar 11, 2005, 8:49 PM   #4
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rob_strain wrote:
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I am a Microwave Radio technician,
Handy to have one of these as a member.

But looking at Requiem's avatar............................do you think it's too late ?
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Old Mar 11, 2005, 11:15 PM   #5
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I don't know, I cant make out what his avatar is.
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Old Mar 12, 2005, 12:54 AM   #6
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Here's a shot taken when I was something like 50 to 75 feet from an AM tower transmitting at 760kHz at 5kW. At night they transmit 50kW. There's a freeway that runs between the towers - you can maybe make out another tower behind the one in the foreground, and there's yet a third tower behind me on the other side of the freeway, from where I'm taking the shot.

note though that the daytime 5kW is non-directional, and I'm not sure which of the 3 towers it uses. Nighttime 50kW is directional and it uses all 3 to beam most of the signal to the west (which is the direction I'm looking in the pic) and north and south.

Actual focal length on the Canon A80 that was shot with was 7.8125mm (translated from 1/1.8" sensor to 35mm that would be about 38mm, or full wideangle on that camera.
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Old Mar 12, 2005, 1:54 AM   #7
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Your camera should be ok since you won't be actually going into the 'danger' zone right? This is for a normal radio station tower. If you get close enough to the antenna, there will be big signs and a big fence that tells you not to go into the zone. That's because when the antenna is transmitting that very high amount of radio-frequency power, it can make mince meat of both us and the camera if we're touching the antenna while touching the ground at the same time (ie electrocuted). Usually we can't get near the antenna anyhow because it's protected, and you have to climb up the tower a little bit first (by stairs or maintenance ladder).

But just to say something about microwave cellular phone base-station towers, which is straying from the subject, it's not such a good idea to get up real close to one of those. Especially, better not stand in front of the microwave transmitter of those base stations. Otherwise might end up getting some permanent health problem, or have kids with three eyes etc.
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Old Mar 12, 2005, 2:00 AM   #8
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rob_strain wrote:
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depending on the power of that antenna, it can be lethal to you
As a chemist who spent a lot of his working life trying to cause chemical changes using RF & microwave energy, I agree in principle.

However, you'd have to sit very near the antenna for a long time for it do anything much. All it's going to do is warm you up a bit. There's nothing magic about RF & microwave energy. The energy isn't great enough to break chemical bonds, except by getting you hot enough if you're near enough for long enough. It's NOT like UV radiation, which is able to break chemical bonds, and therefore cause cancer. When you're gently warmed by the sun, it's IR that's doing it. When you're burnt by the sun, it's UV.

Radiofrequency and microwave energy are lower frequency than the visible range - longer wavelength than IR. UV has *higher* energy, *shorter* wavelength, than the visible. The energy per quantum is proportional to the frequency.When you get sunburnt, it's UV that's doing it.

So don't sit for long too near powerful radio transmitters, but don't worry too much about it. Worry about the lethal short wavelength (UV) radiation from the sun. That's why the ozone layer (which shields us) is important!
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Old Mar 12, 2005, 5:34 AM   #9
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I heard a story about a hot air balloon which crashed into a tower blasting 50kW at 770kHz, while it was ON THE AIR!!. The occupants of the balloon were able to safely climb down the several hundred foot tower, though.

I should mention that the station owners temporarily took it off the air so they could come down, though. I think it was on when they hit the tower.

in case you didn't know, with an AM broadcast antenna the entire tower is radiating, not some little portion at the top. Also this is why some AM towers are taller than others - they usually are a fraction of a wavelength, like most commonly 1/4 or 1/2 wavelength.

Ok, now... if I was holding a camera up to my eye with a 10mm focal length lens, and this was filling the frame, approximately how far away would I probably be?
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Old Mar 12, 2005, 6:01 AM   #10
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pianoplayer88key wrote:
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they usually are a fraction of a wavelength, like most commonly 1/4 or 1/2 wavelength.
You must have very big towers in the USA. In the UK , "Long Wave" AM radio is 1500m wavelength (198kHz) (about a mile), and "Medium Wave" around 909kHz is approx.1500/909*198=328 metres wavelength.
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