How safe is radar ?

FMCW (frequency-modulated continuous wave, aka Navico Broadband) radar uses a continuous, low-power transmission whose intensity is comparable to that of a cellphone transmission. These are "huggable" with a human-safe distance smaller than the diameter of the dome.

Pulse radar sets (anything with a magnetron) should not be mounted where the beam will go through people. There is no risk of ionizing radiation damage, since the photon energy in a radar set is several orders of magnitude too low to shift electrons around within an atom. But there are some tissue heating effects with these high intensity, short duration microwave pulses. Eyes are particularly vulnerable (the eyeball's cooling system is not very effective), as are testes (they don't tolerate heat very well).

Speaking in very general terms:
A small-boat FMCW set will have no effect at all on people.
A 2 kW pulsed set may increase your risk of cataracts if your head is in its beam.
A 20 kW set will noticeably heat human tissue that gets too close to it for extended periods when it's on.
A 200 kW set will cook your nuts and could induce dangerous levels of hyperthermia if you're clinging to the array.

Don't forget the 1/r^2 intensity fall-off; at a boat-length away, none of these will have an appreciable effect on your health.

 

Didn't know about the link with cataracts . Hmmm

Im a full time sailor , with many radar hours on small craft each year. I got senile cataracts when I was 47 years old.

 

When I was much younger (so much younger than today......) I was a fire control technician in the Coast Guard (To you novices, that's gun fire control) They sent me to a Navy electronics school to learn how to operate and repair radars. The fire control radars for guns in those days had far less power output than the consumer radars of today. Yet we were told emphatically Do Not Stand In Front Of A Transmitting Radar!" To press the point they took us to a missile fire control site that stood on top of a heavily forested hill. The trees for at least 1/4 of a mile around the site were all dead.

Of course those missile fire control radars transmitted in megawatts and ours was rated at about 50 kw (WWII stuff) but still it would easily light a neon tube held in front of the feed horn. We used to tell lookouts not to stand in front of it and would hold up a neon tube to show them why.

So It's not a good idea to mount any radar where you are going to be continuously irradiated, unless of course you don't want children. I doubt a single exposure would harm you but continuous just might. Put it up on a spar or radar arch. Besides, up there it has fewer obstructions and better range.

 

PS: I still have a magnetron from one of those old sets.

 

As a much younger lad, I was involved in HERO testing of aircraft ordnance to "local' field power levels of over 200V/m. We would handle the "dummy" missiles and rockets, etc around various airframes, on a groundplane that simulated a carrier deck, in accordance with normal ordnance handling procedures, and a measurement system installed inside in place of the weapon's firing train would relay data via telemetry to a remote recorder. The power being radiated on to us was supposed to be equivalent to the carrier environment; various radar systems (targeting and navigation) and comms antennas.

Watched bright blue fire jump over a foot from a Hellfire in my arms to the helo rack..watched the tail wheel tire on an Apache actually burst in to flame (Army pilot not happy about that)...saw much electronics equipment fried...saw many weapons register induced power levels that would have set them off were they "live".

All these years later (almost 30?), I guess I'm OK....though some would argue otherwise.

 

Welders and glass blowers also get cataracts from the exposure to those rays.

http://cires.colorado.edu/websites/uv/resources/uveyes_final.pdf

http://www.mrcophth.com/ophthalmologyonstamps/phototoxicity/d.html

 

I heard that at one radar station, they had a chicken coup close to the radar, and the eggs were cooked by the radar?

 

Ike, could the fire control radars be rated in terms of average power output while consumer radars today are rated interms of peak power output or pulse power output?

 

I've built a microwave gun that can permanently silence portable equipment like "ghetto blasters" from a considerable distance. It can also defoliate bushes and probably immobilize vehicles. It uses the innards of a commercial 1 KW microwave oven, an aluminum wave guide and a small satellite dish. Pointing it at people probably has serious consequences, so I didn't experiment with that.

I also know from personal experience that target locking radar can fire old fashioned flash bulbs over 100 yards away. But the small marine radar on my boat is pretty harmless compared to that. It does generate 1 KW pulses, but even if it were to transmit continuously, the 2 degrees aperture and 360 degrees sweep would limit exposure to approx 5.5 watts. I consider a cell phone to be much more dangerous.

 

Ok a 20KW radar will do serious damage to human flesh but dont you have to be in its beam?

Being underneath for instance will be ok wont it?

 

I don't think there are 'standards' do decide where it is measured.

All electronics are emitters. Radar is just one emitter you do not want to be close to ....

remember .... distance squared .... 10 feet is MUCH saver than 1 foot.

wayne

 

Ike,

I don't think they read your post ....

RADAR IS NOT A SAFE TRANSMITTER.

Distance, direction, and LEAD SHIELDING are are your best protectors - NOT the strength of the beam ....

If for some reason that SMALL beam were 'focused' at 10 feet .... it no longer matters that you are 10 feet from the source ....

RADIATION IS NOT GOOD FOR YOUR INSIDES. You can argue about melanin in the skin, but that is a DIFFERENT radiation.

If it makes a florescent bulb glow in the dark - what do you think it does to your insides?

BTW, you might take a florescent bulb and 'wave' it around your radar emitter to see where it leaks. You want it real close - an inch. and at night.

wayne

 

a leaking 800watt microwave oven will do more damage as its continuos

 

A 20KW radar unit is a serious piece of equipment, expensive enough to have horn shaped antennas that radiate nearly all energy in a single direction. Directly underneath the antenna unit is a cone of silence, so you are quite safe there, but in the direction of the beam a small amount of radiation is present. Not exactly dangerous, but enough to be measured with a field strength meter.

The small radar units have a much simpler antenna that is just a rotating piece of printed circuit board with many vertical strips that emit the radiation in a horizontal plane. The highest intensity is a 90 degrees angle, but a lot of energy escapes around it. If the dome is mounted on an aluminum mast, the full intensity of the beam is scattered in all directions at every sweep. A bit like washing your car wheels with a powerful water jet: you will get very wet!

 

If you have one. Mine is in storage .... 10,000 miles away.



Radiation is radiation. Just like a fire, it burns whatever it touches. Any other way of looking at radiation reduces safety.