Antenna radiation

[guest]

One of my local towers(1000ft) has two antenna's. (the tower is shared by two t.v. stations One at the very top emmits 5000kW (last time I checked thats 5million watts.) The second one is about 20Meters below and is kicking out 1700kW (1.7million Watts) This seems like a hell of alot of RF to be exposed to.. Will standing at the top, right next to 5million Watts of RF phuk me up? Will exiting just below both emmiters decrease the exposure significantly. Or , should I just avoid this tower all-together?

Somebuddy let me know if they have any experience with similar towers with extremely high output.
Thanks

If anyone would like more info on the tower, post your email address and I will give you the call sign. You can querry the FCC's TV station database and see the specs for yourself.

[guest]

You will get burnt by the rf on this site. I try to stay at least 10' vertical seperation from antennas like this at work. If you attempt this on a humid day the odds of being hurt are even higher. This kind of power can arc to you just being close to the antenna.

later

[guest]

I always stay way lower than the stingers. At least 100 feet away from them and climb really fast above evertything on the way there. Also what is the radiation on the tower away from transmitters? I've always been curious about that...

[guest]

Power radiated along the axis of an antenna is zero. Goes up from there (cos-squared or something) until you get into the plane of the antenna. So as long as you're right under the thing, I don't expect you've got much to worry about.

High frequency radiation (RF, maybe) exhibits a "skin effect", on good conductors (like you), meaning it doesn't penetrate worth a damn. It's always been my opinion (for lack of a better-informed one) that the dangers of RF are significantly exaggerated. Of course, 5 million watts of *anything* might ##### you up, so if you want to play it safe I'd say stay below them or just stay away from them...

As a side note, I've noticed some pretty wierd hardware on my way up a local A. Anybody got a good reference where I can find out what these are? Or know what the sets of helical bits (vertical axis) are about?

[460]

Assuming the transmission is in the usual radio frequency (RF), it essentially heats the tissue. The two organs that are very susceptible to heating are: eyes, gonads. Those are the target organs.

Radiation safety is dictated by TDS: Time, Distance, Shielding.

Minimize your time exposure. Be very ready to jump.

Don't get closer than a few feet from the bottom of the transmitter. Transmitters are designed to radiate to the sides and not downward. However, nothing is perfect and there is some significant radiation leakage both upward and downward. In fact, there are other sources of radiation besides the transmitter -- the waveguide that directs the power to the transmitter. Waveguides are not designed to radiate, but they will if the are damaged or failing mechanically. Waveguides range from large empty tubes to heavy cables, depending on the frequency and power of the subsequent transmitter. The large empty tube-style waveguides are generally evacuated using mechanical vacuum pumps held within the control building at the base of the tower. Anyway, these tube waveguides are stacked one on top of the other. At the junction, sometimes leak develop and radiation may be heavily emitted there. The last time I was on a tower, I noticed a heavy ozone smell which I attribute to a leak in the waveguide. Ozone smells sweet and can be readily produced by arcing or high intensity radio waves.

Never stand beside a transmitter mounted either near the top or on the top of a tower!

Regarding shielding, metal can act both as a shield and as a reflector. If you below a transmitter and there is a lot of metal between you and the transmitter, your radiation exposure may not necessarily be that large. However, If the transmitter is above you and your standing on a big metal platform, assuming the transmitter and you and the platform are in a line-of-sight, your radiation exposure may be substantial.

-Chris, physics doctoral candidate

[460]

BTW, Jess is correct. Radio stations are managable. TV stations that transmit 5MW are deadly dangerous if you too close. They will literally burn you. - Chris

[Nik]

The two organs that are very susceptible to heating are: eyes, gonads. Those are the target organs.

Agree....heat wise

Radiation Wise...
Don't forget most susceptible include organ systems with high cell turn over.....

Skin....the largest organ, (EXCLUDING THOSE OF EUROPEAN DESCENT)...hence increased frequency of skin cancer with UV radiation...

Gastrointestinal System....possibly second only to skin in cell turn over......SO PLEASE..pay attention to GI symptoms...nausea, vomiting, stomach discomfort, diarrhea...etc...these have always been some of the acute signs...... 2 mates I know have
visited local gastroenterologists for such, and received "acute radiation exposure".....in their differential diagnosis...

Treatment: see BASE 386

cheers

BIG Nik...

'tis not the size of the rabbit...'tis the magic in the wand.......yea right

[guest]

I have been to one antenna (TV) where if you stand below the crowsnest you can film with a camcorder no problems but as soon as you pop your head above the floor you get goasting of the tv immage on to the camera footage and then the camera shuts down.
its then batterys out and reset before it comes back to life. funny only one person i know has taken the camera to the top and everryone else gears up below the crows nest and then spends as little time near the stinger as is opssible. eg run to rail and go!
must say the option of exiting fron below the crows nest is not as appealing!
daedalus &-)

[guest]

>Skin....the largest organ, (EXCLUDING THOSE OF
>EUROPEAN DESCENT)...hence increased frequency of
>skin cancer with UV radiation...

Yes, but the mechanism for UV damage to DNA is well-defined, and isn't something *any* amount of RF will achieve before it kills you and burns your entire body to a crispy, dehydrated mass. Which is why I have my doubts about the connection between cancer and acute exposure to RF.

Thanks to Chris, though, for the thoughts on heating and more direct electrical hazards.

[guest]

Thanks for all of the positive input. I think I'm going to stay clear of this particular A. We have so many others just as high, but with way less radiation. (like around 20kW and less) I don't think the reward is worth the risk. Anyway, thanks again. Oh yeah, my gonads thank you too!! :7

[guest]

>Which is why I have my doubts about the
>connection between cancer and acute exposure to
>RF.


No such correlation has ever been claimed with scientific prove...all presently being studied and all presently on the possible list.

[guest]

Let's not confuse ionizing vs. non-ionizing radiation. Ionizing radiation (alpha, beta, gamma, neutron) can be a mutagen and a teratogen as well as the acute somatic effects you describe. Rapidly multiplying cells are more susceptible to those effects which impact the DNA.

However, I would agree that for non-ionizing radiation, like microwaves, the chief hazard is heating. If you put an animal in the microwave, it doesn't die from radiation poisoning; it dies from cooking.

The danger of chronic exposure to EMF is largely anecdotal. You can sue the power company if you live below high tension lines and you get cancer, but you won't win because the science doesn't support it.

P.S. I'm a radiation worker. I picked up a dose of about 40 mR today standing on the reactor vessel, and I feel great!

[guest]

Great. Im screwed. I had taken it for granted that:

1) tower radiation was non-ionizing and therefore substantially less dangerous as the ionizing type of radiation was the sort to do cell and dna damage and was directly linked to cancer.

2) the jury was still out on the harmful effects of electromagnetic radiation, with all current reports listed as inconclusive.

3) The only frequency of electromagnetic radiation readily available to our exposure that causes substantial heating was Microwave emissions, usually emanating from drum shaped pods hung on the tower and noted as highly directional.

4) Current carrying electrical capability affected only objects in contact with a ground, or only converted to an electrical medium if it interacted with an object composed heavily of metal.

These taken as gospel, the primary strategy of dealing with antennas; dont stay on them long, stay off the ones with lots of pods, never get in front of a dish, drum or pod. Run past transmitter elements, and never become the highest point on the antenna. Get up, get off, and get away and your fine.

I know many people who spend substantial time on antennas without damage or harm under these guidelines; why the new strategies listed here im not sure; previous warnings to eyes and gonads have related only to microwave transmissions; standard rf emissions do not have heating characteristics on human tissue, reacting by design with metalwork--when electromagnetic energy interacts with your tv or car antenna an electrical signal is induced which the circuitry of your electronics is resonant with, and translates as instructions to tv magnet deflectors, or more directly as music via speakers. What this posts discusses seems a creole of myths, previous posts, oversimplification, and hard science used overinclusively.

Oh, well. whatever the truth we all die someday. The only question is on what day....

[460]

Yes... 1, 2, and 3, fine...

4..., if you are close enough it can spark to you since you are effecitively at ground.

>4) Current carrying electrical capability
>affected only objects in contact with a ground,
>or only converted to an electrical medium if it
>interacted with an object composed heavily of
>metal.
>
>These taken as gospel, the primary strategy of
>dealing with antennas; dont stay on them long,
>stay off the ones with lots of pods, never get
>in front of a dish, drum or pod. Run past
>transmitter elements, and never become the
>highest point on the antenna. Get up, get off,
>and get away and your fine.
>

all part of the time, distance, shielding (TDS) strategy... Also, High frequency microwaves are notoriously more hazardous than low frequency microwaves. Microwave dishes are substantially higher frequency with the advantage of being highly directional, as you note. When I define RF (radio frequency), I'm following the Department of Commerce's definition, spanning from 3kHz to 300GHz. TV stations operate from 54MHz (below the FM Radio range) to 806MHz (defined to be in the microwave regime) (I don't know where HDTV is allocated). Even FM radiowaves will heat tissue noticable if the intensity is high enough. The higher the frequency, the better the absorption and subsequent heating. The absorption of RF by tissue is very low compared to metal, so you will feel your fillings, ear rings, metal bone hardware, etc. first heat before noticable tissue heating. I also know many people who spend substantial time on these towers. Most of them are the builders themselves, the ATC. Sometimes I've hung out with them an hour at a time 20' below two 5MW TV transmitters. -Chris

[guest]

Chris, basically we concern ourselves with antennas that are the most commonly found and jumped, and are really only concerned with actual damage not theoretical damage. In other words directing people away from specific antennas that WILL burn them, not MAY burn them (or electrocute them) using specific warnings about the frequency/power rating to avoid and what guidelines would identify this great white shark of the antenna world, be it height, or configuration, or whatever the layman can easily identify. Koehler said most of the rest of what i intended and said it well, but I will add, TV antennas in the Microwave range which broadcast from a stinger set-up Ive not heard of; my electronics experience is mostly military;Microwave frequencies are typically used because there is less signal loss at that power and the beam can be directed and focused; this beam or transmission would come from a transmitter hung on the tower, it would not be the tower or stinger itself. Additionally, you make one of my points yourself; antennas have ladders and elevators, rest platforms and crows nests for a variety of workers to change light bulbs and work on the electronic and structural needs of the antenna. These workers are not in space suits and calmly hang out at a variety of points on the antenna, with occupational exposure without exploding on contact with the antenna. Im not saying antennas are good for people, Im just saying dont scare the crap out of people who have regularly been on these things by encouraging tales of burnt intestines, which could only be a product of being in front of a microwave emission array casually.