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Old 25-07-2008, 08:22   #16
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If you don't stand in front of the array in your underwear for a million years you should be fine... The thing you should worry about is exposure to the sun.
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Old 25-07-2008, 10:29   #17
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UV doesn't penetrate the skin to a great depth - and we know it causes damage; prudent sailors recognize this hazard and take steps to protect against it. Microwaves penetrate deep into the body, where they heat the tissues. It is highly debatable that this would ever cause cancer, but whether it does or not, common-sense would rule that "cooking" ones internal tissues, especially the brain cannot be a good thing.
Why would a large microwave penetrate deeper than a small UV wave? It wouldn't. Microwaves heat water by dielectric heating, as a result of dipole (water) rotation. The microwaves themselves stop at the surface of the skin, and heat that surface (from a 2W mobile phone source, placed right on the head) just a fraction of a degree. Much less than the sun does.

I have little doubt that standing next to a military grade radar array for any length of time may kill you, but these are several orders more powerful than the little raymarine boxes we use. Worrying about marine radar is kind of like worrying about raising your bath water 1 degree, because raising it 1000 degrees will kill you.

As for disorientation and nausea induced from a powerful array, I have no idea. Maybe it has to do with the sudden local and uneven heating of the air (dipole heating again) causing havoc with your balance mechanism (like being seasick). I really don't know, just a guess.
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Old 25-07-2008, 10:32   #18
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In a nutshell, the dangers of electromagnetic waves (EMF) boil down to three variables:
1. Frequency, the higher the worse, in general.

2. Power, the higher the worse.

3. Time, the more time you are exposed to EMF, the worse.

I don't worry about yacht radar EMF because I don't have my head 1 meter away from the antenna 24/7. The exposure to EMF power drops with 1/distance squared from the source. So get your body away from the antenna some and you will decrease your exposure to the power variable dramatically.

You get more EMF (gamma radiation) by standing in the sun that you do from a typical yacht radar.

And BTW, nuclear radiation from atomic decay (Alpha and Beta radiation) and radar radiation (Gamma radiation) are very different things. Radars have nothing to do with the decay of atomic particles. Yes, I would be worried too if ionizing positrons, ionizing neutrons and ionizing helium nucleus's were being thrown at me at close to the speed of light...talk about the potential of altering ones DNA! That's not the case with radars though.
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Old 25-07-2008, 10:43   #19
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Alpha partice = He4 nucleus
Beta particle = electron or positron
Gamma particle = any EM radiation produced by subatomic particle decay

Strictly speaking, radar is none of the above. It's EM radiation induced by shaking electrons in a wire with a current.
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Old 25-07-2008, 10:46   #20
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Why would a large microwave penetrate deeper than a small UV wave? It wouldn't. Microwaves heat water by dielectric heating, as a result of dipole (water) rotation. The microwaves themselves stop at the surface of the skin, and heat that surface (from a 2W mobile phone source, placed right on the head) just a fraction of a degree. Much less than the sun does...
It all has to do with the wave length of the electromagnetic radiation. X-band radar, which is what we use on our little boats has a wave length of about 3.2 cm. S-band radar, found on large ocean-going vessels has a wavelength of around 10 cm.

The waves can penetrate solid matter, and remain strong for about 1/3 of their wavelength. The penetrating energy is called an "evanescent wave", and it decays exponentially. Longer wavelengths penetrate more than shorter wavelengths.

An example of how this works is my Sonic brand electric toothbrush. The handle rests in a base to recharge. Neither the toothbrush nor the base has electrodes. Charging is accomplished by the creation of an electromagnetic field using a coil of wire sealed inside the base. Energy is transfered to the battery inside the toothbrush handle through the plastic of the handle.

1 to 3 cm of penetration by high energy EMF is enough to do considerable damage to your eyes, i.e. cataracts.
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Old 25-07-2008, 11:07   #21
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Originally Posted by anotherT34C View Post
Alpha partice = He4 nucleus
Beta particle = electron or positron
Gamma particle = any EM radiation produced by subatomic particle decay

Strictly speaking, radar is none of the above. It's EM radiation induced by shaking electrons in a wire with a current.
Ok, its still the same thing though regardless of the source. Thanks for the precise definition. Radar is EMF, electromagnetic waves at 10cm or 3cm depending on what band you are using.


I find myself guilty of this occasionally, getting distracted by all the instruments and all the other stuff going on inside the boat and not looking out the windows enough:
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Old 25-07-2008, 11:38   #22
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From what I've read, cataracts may be a reasonable concern, with long exposure to high energy sources.

Evanescent wave penetration is different than how UV and other high-energy particles get in and do damage. From what I understand (and I'm NOT an MD) UV (high energy) does it's damage through direct DNA damage, and (low energy) by inducing free radical production in surface chromophores, which in turn directly damage DNA.

A microwave penetrating evanescently decays exponentially as it does so. The 1/3 figure you give is only a sort of 'rule of thumb' to guess at how deep you might expect to reasonably find a microwave particle (they actually penetrate your entire body, though with vanishingly small probability). You shouldn't think that you'll find an even distribution of microwaves in to 1 cm. Instead, you'll find many at the immediate surface, then a sharp drop to vanishingly small at a depth of ~1cm. It won't get to your brain or your internal organs.
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Old 25-07-2008, 12:05   #23
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... and be courteous.

It's a good idea to turn radars off while at the dock, in an anchorage or on mooring.

Of course, it's not cruising sailors that keep them on for hours after they arrive... it's usually a large power vessel.
Because everyone knows how "cool" it is to motor around the harbor on a clear day with your radar turning.
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Old 25-07-2008, 12:10   #24
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The point of this thread was do we need to worry about radar. The answer is, theoretically, yes; practically, no if you take reasonable precautions.

Here's the safety warning from the Raymarine Radome manual. It applies to both the 2kW and the 4kW models.

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Old 25-07-2008, 12:23   #25
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[quote=anotherT34C;186479]From what I've read, cataracts may be a reasonable concern, with long exposure to high energy sources.

As Sailors/Cruisers, it is worth noting that UV radiation exposure is a major causative factor in the formation of cataracts. As most of us are in the sun (a real nice source of UV) with polarized but non-UV filtering lenses, we are exascerbating the problem because, as our pupils are artificially dilated, we are letting more of the UV to our own lenses. As well, roughly 50% of the general population will have some form of cataract by age 65 with this number rising to 75% by age 75.

So, your best bet, if you can find them, is a pair of Polarized lenses with UV protection. Oh, and you probably don't want to stare directly into your active radar.

Personally, cataracts would not be my main concern. Melanoma from sun exposure tops that list.
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Old 25-07-2008, 14:47   #26
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Cataracts are a definite concern with radar exposure in a previous life I was an optometrist and had a patient who was a radar technician. He developed dense sub capsular poster polar cataracts in his late 30s.
However if you install radar sensibly I feel the risk of cataract is still increased far more by UV exposure caused by the outdoor lifestyle associated with sailing. Use sunglasses or if you wear prescription glasses replace the lenses with a high index plastic lens that can have excellent UV absorption even though they are completely clear. It will also be thinner and lighter.
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Old 25-07-2008, 17:40   #27
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As a USN radar tech, I wouldn't stand infront of ANY radar going round and round, regardless of mil-grade or not. We even paint the restricted space around an array red to warn people (even the civilian radars we use). I could, but wont, dredge up all of the information about klystrons, magnetrons and the formula for Q just to uber-speak my way to the top of this post, and illustrate the point that electromagnetic radiation in a concetrated form is not good for you. Radar is a focused beam of energy and it is that focusing that makes it more dangerous than the broad splash from the sun. The klystron in your radar is the same as your microwave. Would you put your head in the microwave?
I would mount my ray-dome as high as possible to avoid incidental radiation, but mostly to increase my "sight" horizon.
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Old 25-07-2008, 18:46   #28
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Thanks for all the answers, I'm having Crazy Lady re-rigged & while the mast is out I was thinking of moving the radar from the transom pole to the mast. Now my feelings?

Does anyone want to buy a used radar????
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Old 25-07-2008, 19:04   #29
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I'd not ditch the radar as getting run down by a container ship in the night removes the uncertainty factor rather nicely. Stick it way, way up the mast.
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Old 06-08-2008, 07:44   #30
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radars have an angle like a cannon so beneath it u'r saved (cca 15m of radius on cargo ships) or if you are hiding around a mast/ object; on cargo ships, radars have derricks infront so there's a dead angle -> a lot of collisions happens this way!!; thay simply didn't see u; the only solution is steering for few in order to see whats infront of the derrick
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