RF exposure from marine radar

T

triton1

New member
I need someone out there that is up on their trigonometry? My new installed radar has a vertical beam of 25 degrees. The center of the radar beam is approx. 2ft. 7in. above the cabin top. I would like to know how many feet from the antenna does the lower 12.5 degree beam intersect with the cabin top plane? Thanks.

Robert Healy
Fan-C-Dory
 
2'7" = 31 inches

31"/TAN(12.5) = 139.8" = 11.65 feet ~ 11'8"

So... assuming that the radar post is perpendicular to the roof (and that my math is correct), the beam would intersect your roof 11-feet, 8-inches away from the post.
 
Rough numbers are 11.3 feet. That should be well clear of both your head in the cabin, and the V berth (for there the height would be considerably more). Even with big ships radar (I have seen a photo, and it does not look at all bad)--you are going to be safe. The issue areas are mostly the eyes and gonads.

However, the "Beam width" is not really a sharp cut off--there is some radiation below this. But the amount of exposure you would get is still not significant.

Now another question--did you put the 4 degree down wedge under this radar? If so, that will change the geometry--and the distance would be 8.6 feet, you would still be clear.

I used 2.5 feet for simplicity, and rounded at the second place.
 
Yep - 11' 8". Here's an image to make the math a little clearer.
RadarTrig.sized.jpg

Also note that with the new digital broadband radars from many manufacturers the power levels are MUCH lower and no longer a concern.
 
I forgot we did have the 4 degree wedge installed. So the bottom of the beam would still be above our heads? I was wondering if side lobes would come in to play, providing scattered EMF below the actual lower bottom beam? Thank you both for your help in the math department. I feel much better about our exposure risk after reading your opinions.

Robert
Fan-C-Dory
 
triton1":1ezlfrgd said:
I forgot we did have the 4 degree wedge installed. So the bottom of the beam would still be above our heads? I was wondering if side lobes would come in to play, providing scattered EMF below the actual lower bottom beam? Thank you both for your help in the math department. I feel much better about our exposure risk after reading your opinions.

Robert
Fan-C-Dory
Click to expand...
The distance is about 8'8" with the 4 degree wedge installed.
 
I do not believe that there are any significant health risks from your radar (a medical opinion--free) There are actually more from the cell phone if you put it up to your ear, instead of using blue tooth.
 
Thanks Dr. Bob, I will sleep well tonight! Oh yes, I am going to use the speaker phone or blue tooth from now on..........................

Robert
Fan-C-Dory
 
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