Radar Radiation

T

thunderbird1

New Member
Oct 4, 2006
365
Pacific Northwest
When we're tied up at public docks along the Columbia River, we often observe boats with their radar scanners still spinning for 5-10 mins after they have docked. I asked one skipper last week (after his radar had been running for about 20 minutes) if he could please turn his radar system off. He did, but looked at me like I was insane -- which I may be, of course. I had assumed that his radar was blasting my kids with radiation as the scanner merrily spun round and round 40 feet from my boat .

Is there a health issue associated with running radar at the dock?
 
I'm sure there are others on the board who can more fully answer the dangers, if any, from the radiation emitted from a radar, but I agree with you. Why expose anyone to any additional radiation unnecessarily? I turn my radar off as part of my "before landing checklist" outside of the marina or anchorage.
 
I also turn off my radar before getting into a harbor/marina.... But I do fire it up before I leave the dock to make sure it is working.

I watched a guy dock at St. Michaels last month in a 380 and his radar was running... he looked like an idiot IMO... His wife was on the bow and the radar was blasting right into her.
 
Are there any warnings located in the radar manuals? Should show recommend distance versus level of irradiation.

I was part of a safety class a number of years back on a piece of equipment my ship had on it. We used a egg as a test subject. The fire control officer lite up the radar, narrowed the beam and walla! We had a hatched chicken. Moments later we had cooked chicken and after that we were hunting barbecue sauce. :smt038

Moral of the story, keep barbecue sauce always handy, it covers up the burnt parts. :smt043
 
thunderbird1 said:
I had assumed that his radar was blasting my kids with radiation as the scanner merrily spun round and round 40 feet from my boat .

Is there a health issue associated with running radar at the dock?
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I think the short answer is that if you stay at least 1 meter away from the radar antenna, then you are OK. This assumes a consumer radar of about 4 KW.

If you are 40 feet from the antenna, then the exposure is reduced by over 100 compared to being 3 feet away.
 
Well. . .there is radiation, then there is :smt101 radiation :smt101.

Light from a lightbulb, radar emmissions, microwave ovens, and cell phones ays all are radiation sources. The question is the POWER and WAVELENGTH of the emmission.

I would look at the radar user manuals for guidance on this topic. Manuals for that type of consumer electronics would be very explicit and very conservative.
 
From the manual:

2. ELECTROMAGNETIC ENERGY. The radar scanner transmits electomagnetic energy. It is important that the radar is turned off whenever personnel are required to come close to the scanner to perform work on the scanner assembly or associated equipment.

It is recommended that the radar scanner is mounted out of range of personnel (above head height)

Avoid looking directly at the antenna as your eyes are the most sensitive part of the body to electromagnetic energy.

When properly installed and operated, the use of this radar will conform to the requirements of ANSI/IEEE C95.1-1992 Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3Hz to 300 GHz and NRPB, Board Statement on Restrictions on Human Exposure to Static and Time Varying Electromagnetic Fields and Radiation. Doc NRPB, NO. 5 (1993).
 
I always wondered about those boats with radar installed in front of the flybridge - right between the captains legs.
 
You know. .. this is why the country is going to pot. Explanations like what is in the manual that Dominic quoted.

The manual implies "Electromagnetic energy is bad". oooohhh. Electromagnetic energy is baaaad. stay away. (Please don't sue us.).

Is too hard to state a minimum safe working distance? I guess so. geez. What's with people?

Folks, SUN LIGHT is electromagnetic energy. Yes. . .your eyes are sensitive to electromagnetic energy. That is how VISION works.

http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html

The question is how much POWER the darn radar puts out and at what wavelengths. Then you can determine a safe distance. R.A.D.A.R. stands for RAdio Detection And Ranging. (If I remember correctly). It's just a high power radio transmitter and receiver.

http://en.wikipedia.org/wiki/Radar

The issue is that Radar units put out a good bit of power -> thousands of times more than your handheld VHF radio. How much you are being fried by the darn thing is a function of the POWER and the RANGE.

If I remember correctly, Power = (fudge factors) / (distance squared)

So if you double your distance from the radar unit, your exposure goes down by a factor of four. If you increase your distance by a factor of 10 (10 feet to 100 feet), you drop your exposure by a factor of 100.

Bottom line: Don't stand right in front of the thing! It might fry you!

Your cell phone also puts out electromagnetic radiation (it has a radio transmitter afterall). Cell phones are considered safe because they are low power devices. The issue with cell phones is that the RANGE is really, really short. (where is your ear relative to your brain?)

BTW: Don't put your nose on your computer monitor.

- - - - - - -
 
comsnark said:
You know. .. this is why the country is going to pot. Explanations like what is in the manual that Dominic quoted.
...
Is too hard to state a minimum safe working distance? I guess so. geez. What's with people?
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:grin: It really has nothing to do with the country going to pot. That is happening with or without radar! The statement in the manual Dominic quoted was totally useless to answer what Presentation asked, in a sense. It directly provided no information about how close.

But indirectly, it answered the question. If you are below the radar, not on the same horizontal plane as it, you are OK. That's because the bean goes out more or less horizontally. Note that is only a recommendation though. It states if you are going to work on the radar antenna unit, it must be off. So if you are within arms reach of the antenna, and in front of it, it must be off. Your arms are about 3 feet long. So that (arms length), very indirectly, is their answer in the case of being on the same horizontal plane.

comsnark said:
The issue is that Radar units put out a good bit of power -> thousands of times more than your handheld VHF radio. How much you are being fried by the darn thing is a function of the POWER and the RANGE.
Click to expand...
This is partly true. It is a function of power and range. But the average power put out by the radar is not really so much different than a handheld radio. A handheld may put out a watt or two. The radar puts out 2000 or 4000 watts when it is on, but it is almost always off. The transmitter is on typically less than 0.1% of the time. So for a 4KW transmitter that is on 0.1% of the time, the average transmit power is 0.1% of 4KW, or 4 watts.

comsnark said:
If I remember correctly, Power = (fudge factors) / (distance squared)

So if you double your distance from the radar unit, your exposure goes down by a factor of four. If you increase your distance by a factor of 10 (10 feet to 100 feet), you drop your exposure by a factor of 100.
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Exactly true.

comsnark said:
Your cell phone also puts out electromagnetic radiation (it has a radio transmitter afterall). Cell phones are considered safe because they are low power devices. The issue with cell phones is that the RANGE is really, really short. (where is your ear relative to your brain?)
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True again. I would be very surprised if you didn't get more brain radiation from using a cell phone that you do from the radar at 15 feet.

I changed my answer in my first post above from 3 feet to 1 meter, because if I post calculations, they will have to be based on the metric system. And 3 feet is a meter, close enough for "government work".

I found the Raymarine radar manual , page 5 of the pdf, to be more helpful. It says 1 meter in front of the antenna for the lower exposure limit of 10W/sq meter, worst case. So I think it is also suggesting 1 meter minimum. But the number (10W/sq. meter) is in the wrong format (should be expressed in mW/sq. cm), and is ten times above what I think is the acceptable limit. I think the number is wrong.

Guess I might as well write down my thinking here. From the Raymarine manual, pdf page 29, the pulse length is 1 uSec, and the prf is 740 Hz for a range of 6 nm or more. This means it is on for 0.07% of the time. Multiply that by the 4KW rating of the radar, and you get 3 watts average.

At a distance of 1 meter from the antenna, the vertical height of the beam is about 6 inches, or 1/6th meter (WAG , but useful to calculate with). The circumference of a circle 1 meter from the center of the antenna is 2pi times the radius of 1 meter. Pi is 3, so 2 pi is 6. So the circumference is 6 meters. The area of a surface the beam radiates is the circumference times the height at one meter (1/6 meter assumed). So the area is 6 meters times 1/6 meter, or 1 sq. meter. So we have 3 watts average radiating 1 sq meter, or 3 W/sq. meter.

Changing this number to the correct format, it is 30mW/sq. cm. This is a number that you can compare to an exposure guideline from IEEE. If you go to the link, scroll down to the first chart, you will see at 3 GHz the controlled environment limit is 10mW/sq.cm. So the number Raymarine quotes is ten times too high for continued exposure per IEEE.

As comsnark states above, if you double the distance, you reduce the exposure by a factor of 4. So at 2 meters, the 30mW/sq.cm I very roughly calculated would be reduced to 8 mW/sq. cm. That is reasonably in line with the IEEE spec.

Oh, here is Ontario's specification on the exposure level.

Bottom line, I think that my original posting of 3 feet is safe is arguable, and depends on variables I can't know for sure. Two meters seems to be about the IEEE limit from my rough calculations. At ten feet, I think you are OK. So if the radar antenna is not on your boat, then it should not pose a problem.

The thing least well defined in all the above is the vertical height of the beam. At a distance of 3 feet, you are in what is known as the "near field" of the antenna, and calculations fail. At 10 feet you might be in the "far field", especially in the vertical dimension. All the references assume non-ionizing radiation, which I believe to be valid. It takes quite a bit of power to ionize things.
 
Your arms are three feet long !!!!!!!!!!!!!!!!! :huh:

Must suck to have to stoop under the radar arch.
 
FWIW, garmin's manuals specificly state that you should not look into the radar's path as the eyes are most sensitive to the radar electromagnetic pulses. (Funny how the radar is one of the first things I look at when checking out a boat in a slip!)
 
Just because it is spinning does not mean it is radiating... It could be in a standby mode couldn't it?

The eyes are the most effected by the radar radiating.
 
It is important to note that radars emit electromagnetic energy, not ionizing radiation as you would get from a radionuclide like Cobalt 60 or Americium 241 or from an X-ray machine. Two different things entirely. It's not "radiation" in the sense that most people think about. There are no alpa particles, beta particles or gamma rays. Fuggettaboutit.

I should know. I was a licensed radiation safety officer.

Dennis
 
This thread kind of gets back to a question I asked earlier this summer about why people feel the need to run their radar on an otherwise clear day. Other than the cool spinny thing, of course.

The bottom line was that one could interpret Rule 7 of the Colregs to insist upon running the radar at all times while underway. If I recall, Rule 7 requires "the proper use of Radar, if so equipped" or something close to that. Of course, one could also argue that the term "proper use" leaves ample room for interpretation.

Personally, I don't think running that radar while docked (other than firing it up on the way out) or while underway in a tight harbor on a clear day constitutes "proper use".

But... it appears that from some of the technical data presented earlier in this thread, it probably is harmless.

OK, for the punch line.... If something is probably harmless (meaning there is a slight chance it might be harmful) AND it offers no benefits because you are already tied up to the dock, why do it?

Unless there's a thunderstorm is in the area...
 
Running the radar on a clear day does 2 things. First, it does satisfy rule 7. Second, it breeds familiarity with the radar. If you know what it looks like on a clear day when you can compare targets on the screens to what you actually see, it is far more valuable when you cannot see actual obstacles and have only the radar to depend on.
 
RT 240SD said:
Your arms are three feet long !!!!!!!!!!!!!!!!! :huh:

Must suck to have to stoop under the radar arch.
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When I go to Wal Mart to get a couple of yards of cloth, I measure a yard by holding the end of the roll in my left hand, extending it straight out to the left, and grabbing the cloth at the tip of my nose. That's a yard. I figure that is close enough that I can refer to my arm as three feet. It may not be exact, but I rounded all the numbers. Precision is not important when striving for a rough cut answer.

My 270 Sundancer does not have a radar arch. :smt089 If it did, I would have a fake plastic radar antenna mounted on it like I do on my pickup truck.
 
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