Author Topic: Large HF transmitter 200kw AN/FRT-62 and health effects  (Read 8081 times)

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Offline Zero999

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Re: Large HF transmitter 200kw AN/FRT-62 and health effects
« Reply #25 on: September 17, 2015, 11:50:16 am »
It's not just the power output or frequency but how concentrated the beam is.

A large bonfire could easily be outputting more than 500kW of radiation (mostly in the IR but there will be some in the microwave band as well as the visible) but because the energy is radiated in all directions so one has to be pretty close to it to suffer burns or eye damage.

A magnetron produces a more concentrated beam of radiation so it's much more dangerous. Yes it's true that 2.45Hz penetrates the human body more than IR so it presents a greater danger to the internal organs but the main hazard is the concentration of energy. An IR laser with a power output of just a couple of Watts will blind you instantly.
 

Offline T3sl4co1l

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Re: Large HF transmitter 200kw AN/FRT-62 and health effects
« Reply #26 on: September 17, 2015, 12:04:45 pm »
Well no, magnetrons don't produce more concentrated beams than IR...

Lasers can cause instant blindness due to vaporizing the retina in spots, but magnetrons certainly won't do the same.  If you're in a field intense enough to do that (say a military radar), you're damn well going to feel it on the rest of your body, and run the fuck out of there because it feels like being roasted alive (which is what's happening)!

Eyes are basically water, about 8 mL worth.  Which might be damaged quickly by a modest 5C temp rise, which will take 170 J, or over 1kW actually absorbed by the eye and nothing else to cook it in "a fraction of a second" (which is still considerably longer than 'instantaneous', but I'll give this one for human terms of 'instantaneous').  Which would be an impressive feat, in the middle of a face, for a microwave field no more energetic than 1kW.

I don't suggest pointing the magnetron antenna tip at your eyeballs, but I don't find common magnetrons themselves to be a special concern around things made of meat (except for long exposure).

Tim
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Offline VK5RC

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Re: Large HF transmitter 200kw AN/FRT-62 and health effects
« Reply #27 on: September 17, 2015, 12:22:57 pm »
@ez24 memory is not a limitless resource, from my understanding reasonably frequent use of a memory is needed to maintain it although some are locked in at an early stage, typically by very strong emotional stimuli.
There are age related changes in cognitive function, one of the main ones is the decline in multi-tasking. I am noticing this in my early 50s, to a subtle degree, esp when driving a car, previously could do lots of stuff e.g. drive close to the speed limit, radio up loud, look at the pretty girls etc. Now if the traffic gets busy the radio goes down, eyes on the road.
Anxiety can also cause an apparent cognitive deficit by diverting attention so worrying about your memory won't help!!! HiHi.
Whoah! Watch where that landed we might need it later.
 

Offline AF6LJ

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Re: Large HF transmitter 200kw AN/FRT-62 and health effects
« Reply #28 on: September 17, 2015, 01:01:53 pm »
It's not just the power output or frequency but how concentrated the beam is.

A large bonfire could easily be outputting more than 500kW of radiation (mostly in the IR but there will be some in the microwave band as well as the visible) but because the energy is radiated in all directions so one has to be pretty close to it to suffer burns or eye damage.

A magnetron produces a more concentrated beam of radiation so it's much more dangerous. Yes it's true that 2.45Hz penetrates the human body more than IR so it presents a greater danger to the internal organs but the main hazard is the concentration of energy. An IR laser with a power output of just a couple of Watts will blind you instantly.
The above statement is not true a magnetron radiates like a 1/4 vertical antenna.
The output terminal is a probe that is designed to be inserted into a waveguide. The Waveguide gives it directonality, and concentrates the enegry. At power levels seen in microwave ovens it is still harmful, without a waveguide. .
Sue AF6LJ
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Offline Zero999

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Re: Large HF transmitter 200kw AN/FRT-62 and health effects
« Reply #29 on: September 17, 2015, 04:51:20 pm »
Lasers can cause instant blindness due to vaporizing the retina in spots, but magnetrons certainly won't do the same.
It depends on the wavelength of IR which covers a huge bandwidth from about 300GHz to 400THz. The shorter wavelengths will penetrate deep enough to damage the retina but the longer wavelengths will be absorbed closer to the surface of the eye and cook your eyeball.

The above statement is not true a magnetron radiates like a 1/4 vertical antenna.
The output terminal is a probe that is designed to be inserted into a waveguide. The Waveguide gives it directonality, and concentrates the enegry. At power levels seen in microwave ovens it is still harmful, without a waveguide. .
Yes you're right, I stand corrected.
 

Offline SeanB

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Re: Large HF transmitter 200kw AN/FRT-62 and health effects
« Reply #30 on: September 17, 2015, 05:17:53 pm »
Problem with the eye is that the cornea has no actual pain receptors, only the lids and the inner layers have nerve endings. Thus you will not feel pain from having the actual cornea cooking, though it only has to rise over 45C to actually cloud over from the proteins denaturing. You often find welders with corneal damage from looking at the unshielded arc when striking.

As to the radio station broadcasting over a border and needing to make a directional array that is all a matter of changing the radiation pattern from an omnidirectional to a directional one, by using extra antennas fed with a phase shifted signal ( really large high power air cored inductors and high voltage capacitors in a doghouse near each antenna element to do the phase shift) so there is a higher power signal radiated in the desired direction, with a reduced pattern ( along with some nasty side lobes as well) to the chosen side. Basically a very large Yagi antenna, just with the phase shift provided by LC circuits, not by making reflector elements longer and directional elements electrically shorter.
 

Offline calexanian

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Re: Large HF transmitter 200kw AN/FRT-62 and health effects
« Reply #31 on: September 18, 2015, 08:02:49 pm »
+1 for HF is less of a concern. Exposure limits become more of a concern as frequencies increase. Additionally most of the equipment used in military/commercial applications used hard line and lots of shielding in their respective enclosures. Where things get tricky is VHF and above high power experimental things where people are hovering about in close proximity to very high power high frequency and more thought is given to experimentation and testing rather than safety. Generally speaking though in a commercial piece of equipment whos antenna radiating surface is up a tower outside somewhere a hundred feet or more away you have little to worry about. If you are 10 feet from a multi kilowatt UHF transmitter antenna I would say find a new job.
Charles Alexanian
Alex-Tronix Control Systems
 

Offline AF6LJ

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Re: Large HF transmitter 200kw AN/FRT-62 and health effects
« Reply #32 on: September 18, 2015, 10:52:05 pm »
Just to add a date point to this.
My Paternal grandfather was an iron worker he had his own business providing parts for the Cold War. He had iron worker's cataracts. I pestered my father to take to me Grand-Pa's business and got to see what went on there. The amount of IR radiation this man subjected himself to was amazing. Heat treating special missile parts in a -40 degree caustic soda bath that were orange hot when they came out of the furnace, it was like a walk through Hell.
He had his eyes needled twice for cataracts. An amazing man who learned metallurgy when it was still an art.
IR is much worse than RF when it comes to the damage it can do.
Sue AF6LJ
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Offline SeanB

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Re: Large HF transmitter 200kw AN/FRT-62 and health effects
« Reply #33 on: September 19, 2015, 01:29:48 pm »
Snap, Grandpa was a patternmaker, at a foundry that made munitions. The patterns he made are probably still in use, as bomb design has not really changed much since WWII, though the accuracy has improved somewhat. They all still hit the ground, but the spread has improved from "somewhere within vision" to "Don't be the target".

Still have his retirement dish they made for him there.
 


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