How does radar affect my body?

[Lepke]

There's a report out that cell phone increase the risk of tumors. Radar beams at close range are a lot more powerful.
On the positive side, it might reduce the risk of paying child support.

 

[JWellington]

"Boat radars are not dangerous; they don't pose any threat to humans because they emit non-ionizing radiation, which doesn't penetrate the human body. Radiofrequency fields above 10 GHz at power densities over 1000 W/m^2 are a risk; but, those numbers are “far away” for a normal radar most boats use."

 

[Hippocampus]

Found post #59 helpful but still confused. So thought given the beam is focused and not a point emitter the inverse square law doesn’t apply. Kind of like a lazer but not to the same extent. More like a flashlight but with a really good reflector or lens to focus the beam. Excuse my ignorance which is it?

 

[stubones99]

Found post #59 helpful but still confused. So thought given the beam is focused and not a point emitter the inverse square law doesn’t apply. Kind of like a lazer but not to the same extent. More like a flashlight but with a really good reflector or lens to focus the beam. Excuse my ignorance which is it?

There is some beam spread with distance, mostly due to refraction in the air. The accuracy of the beam depends on the size of the reflector, so larger reflector, the better aim it will have. That's why bigger boats often have a larger open array, even if they use a wide beam radar for up close.

Yes, the beam is line of sight, so distance depends on height of the antenna. Anything beyond the visible horizon goes off into space.

 

[OldDan1943]

There's a report out that cell phone increase the risk of tumors. Radar beams at close range are a lot more powerful.
On the positive side, it might reduce the risk of paying child support.

Lepke, and sleeping with someone else's wife is risky too.

 

[Hippocampus]

So beam doesn’t follow inverse square law?

 

[stubones99]

So beam doesn’t follow inverse square law?

Inverse square law is for radiation from a non-focused source. A directional antenna breaks inverse square law since it redirects the majority of the radiation where the designer wants the radiation, rather than having a candle emitting light in all directions.

Beam spread does happen though, due to refraction, hitting moisture, dust, and even air... In space, in a vacuum, there would be less beam spread.

 

[Hippocampus]

Perfect. Thanks. Confirms original thinking. So given there’s scatter and beam spread is that of any practical concern when mounting multiple radar units? Is there vertical distance apart they should be?

 

[twistedtree]

Unfortunately, I don't have any hands on experience with 3D wideband radars but they use a lower broadcast power level, so their danger should be greatly reduced.

With a so-called broadband radar, the transmission is at a lower power - true. I have seen figures of 250W and 600W vs 4kw, 12kw, 25kw for a pulse radar. But that's only half of the story, as edited by the marketing department. With a broadband radar, the transmission is continuous, where with a pulse radar - you guess it - transmits short pulses. As a result, the total emitted energy is nearly the same between the two. This show in the published safe-distance numbers which differ by <1 meter, and often much less. It's just not a very big difference, but vendors (Simrand in particular since they popularized it) have convinced everyone there is a huge difference. There just isn't.

The way Radar works is it broadcasts a narrow beam with one directional antenna, and a secondary antenna a few degrees off of the broadcast antenna picks up the reflected signal. The degrees between the two antennas is how they set the range, since a distant target would require a greater time for the signal to get to the target and bounce back. Some systems slow down the rotation speed to adjust range, others adjust the delta angle between the two antennas.

This is interesting, but different from my understanding of how at least marine radar works. Perhaps there are different types. I don't know.


My understanding of marine radar, and until now I thought all radar, is that distance to an object is measured by timing the return of the signal. You are saying the same thing, but I think you are also saying that's measured by how much the antenna has rotated when the return signal is received. Everything I've read says that it's measured by simply timing the return signal. Since the pulse propagates at the speed of light, it's out and back pretty darn fast. Fast enough, I think, that any rotation of the antenna will be imperceptible. A quick calculation says that with a 24 rpm antenna, a degree of rotation takes 7ms. The propagation time for the pulse to and from a target 96 miles away is only 1ms.


Rotation speed is really about getting more position fixes per minute.

 

[twistedtree]

Inverse square law is for radiation from a non-focused source. A directional antenna breaks inverse square law since it redirects the majority of the radiation where the designer wants the radiation, rather than having a candle emitting light in all directions.

Beam spread does happen though, due to refraction, hitting moisture, dust, and even air... In space, in a vacuum, there would be less beam spread.

hummm, I really don't think so. The focusing of the beam concentrates the available energy into a narrower focus. So you end up with more energy "shining" on a smaller area. But it still falls off based on the square of the distance. There is just a lot more of it to begin with since it's been focused.

 

[fgarriso]

Since I only have two brains ( Left & Right ) with a limited number of brain cells, and getting less every day. I think I will keep the few I have left, and mount the radar antenna
overhead.

 

[twistedtree]

Perfect. Thanks. Confirms original thinking. So given there’s scatter and beam spread is that of any practical concern when mounting multiple radar units? Is there vertical distance apart they should be?

Beam spread is because the beam projects out at an angle. The bigger the antenna the smaller the angle, but it's still an angle - say 1 deg as an example. So the area covered by that beam gets wider and wider the further away the target is.


Kevin Monahan's "Radar Book" has been referenced in this and other threads when radar has come up. It's a good read and covers all this, as I recall. Furuno's operator's guides are quite good too in covering the basics.

 

[Marco Flamingo]

Just found a used copy of The Radar Book. Also saw that the same author has a GPS book. That's next.

Last radar scare I read about was don't have it at eye level. Eyes bad but brain okay? I went with neither and want it up above.

Got a lot of radar use on the weekend of the 4th. Passed Point No Point in 70 feet without a visual on the lighthouse or even the beach. Something passed me to the west at the same time. Odd thing was there were hundreds of small fishing boats at Possession Bar and somebody had an open mike on 16. No easy way to contact the mystery bogie or anybody else. Open mike lasted 30 minutes, CG came on and notified about open mike, then it happed again about 15 minutes later.

Once the fog had cleared, I used a bearing circle on the radar screen and then my pelorus to get s visual on remote bogies. I found that the bogie generally appeared >4 or 5 degrees to the right of the pelorus bearing. It is easy to ensure that the pelorus is registered correctly with the boat's centerline. Is it possible for a radar to be off several degrees? Is a correction by adjusting the dome or electronically in the MFD?

This could also be anothert reason why radar on a day marker and GPS don't always agree.

 

[backinblue]

I'm probably missing something, but how does a CG warning about an open mike reach the violator? BTW, we also have a Point No Point in Stratford, CT.

https://portal.ct.gov/-/media/DEEP/gis/coastalaccessmaps/CoastalAccessSite330.pdf

 

[SteveK]

I'm probably missing something, but how does a CG warning about an open mike reach the violator? BTW, we also have a Point No Point in Stratford, CT.

https://portal.ct.gov/-/media/DEEP/gis/coastalaccessmaps/CoastalAccessSite330.pdf

One of the amusing moments on the water.
Each time I wonder if the newbie operator is told to make the broadcast and then go to storage room to get a skyhook.

 

[OldDan1943]

One of the amusing moments on the water.
Each time I wonder if the newbie operator is told to make the broadcast and then go to storage room to get a skyhook.

Compass grease and 50 feet of shore line.
“Set the mail buoy watch.”

 

[Hippocampus]

TT is right and I’m wrong. Radar does follow inverse square law. Here’s a discussion about strength.

https://www.testandmeasurementtips.com/the-inverse-square-law-and-radar/

 

[Marco Flamingo]

I'm probably missing something, but how does a CG warning about an open mike reach the violator? BTW, we also have a Point No Point in Stratford, CT.

https://portal.ct.gov/-/media/DEEP/gis/coastalaccessmaps/CoastalAccessSite330.pdf

Channel 16 opened up for a few minutes and the CG immediately sent the message. It apparently didn't reach everybody or somebody else sat on their mike. I really don't know how open mike situations arise. When it is kids, you can usually hear them giggling.

 

[Knot Salted]

Pete,
I am a cautious type. For me, I would not install the radar dome right in front of where I plan to sit all day. Plus, I would not be happy with a radar that only showed about 180 degrees (only in front) of my situation. In fog, especially in a slow trawler, you can be overtaken from astern or at an angle that your radar would not show! This would mean that the radar would only be about 50% effective and in a way give a false sense of security.

Minimizing your personal exposure to any form of radiation is never a bad thing!! Mount it on your mast where radiation exposure would be basically non-existent, where it can operate as designed giving a complete "picture" of your "environment", and figure out a way to lower the mast in a safe, easy manner.
Why would you want to operate in a "lose/lose" manner where the radar operates way less than optimally and at the same time might actually be causing damage to your long term health? Just my humble opinion.

This is the camp I am in.
I find it inconsiderate and careless when someone enters a marina with their radar antenna spinning madly to no purpose other than to show it.

Ours is mounted as high as is possible on KS.

 

[Chuck16]

I was a RADAR tech in the US Navy. Yes, consumer boat RADAR is less powerful than air or surface search RADAR we used in the military. The radiation hazard (RADHAZ) should be published for every unit. If not it can be calculated. RADHAZ is a distance.

Like your microwave oven, it heats water best and less dense materials absorb less energy from the radiation. Think, eyeballs, testicles , and yes, brain. But, everything is absorbing that RF energy.

If your RADAR transmits down a small size coaxial cable instead of a mechanical "Wave Guide" you can be pretty sure it's low power. You can google wave guide I would guess to learn more. However, the damaging effects are not really reversible and are cumulative. I will not choose to sit in front of a RADAR that is operating for any length of time. Especially for a 10 hour day, every day, doing the ICW or LOOP. Why do it? Vanity?

I liken it to my well at my house for my drinking water. The level of arsenic in the water is right at the limit. The guy that owned the house before me for 40 years drank it everyday. Eventually he got cancer at age 88 and so did his wife. The cause unknown.
I present to you two glasses of water to drink for the next 10 years, one with the technically safe level of arsenic and one that's pure. Which one would you choose?

I would counsel everyone to put their RADAR up above the human habitation level on their boat and know that if you ever get cancer/brain tumor/sterility it at least was not from your boat.

Respectfully,

Chuck

 

[JWellington]

Looks like nobody believed the quote I found about it not being dangerous. So you'll just frett over nothing.

 

[twistedtree]

I was a RADAR tech in the US Navy. Yes, consumer boat RADAR is less powerful than air or surface search RADAR we used in the military. The radiation hazard (RADHAZ) should be published for every unit. If not it can be calculated. RADHAZ is a distance.

Like your microwave oven, it heats water best and less dense materials absorb less energy from the radiation. Think, eyeballs, testicles , and yes, brain. But, everything is absorbing that RF energy.

If your RADAR transmits down a small size coaxial cable instead of a mechanical "Wave Guide" you can be pretty sure it's low power. You can google wave guide I would guess to learn more. However, the damaging effects are not really reversible and are cumulative. I will not choose to sit in front of a RADAR that is operating for any length of time. Especially for a 10 hour day, every day, doing the ICW or LOOP. Why do it? Vanity?

I liken it to my well at my house for my drinking water. The level of arsenic in the water is right at the limit. The guy that owned the house before me for 40 years drank it everyday. Eventually he got cancer at age 88 and so did his wife. The cause unknown.
I present to you two glasses of water to drink for the next 10 years, one with the technically safe level of arsenic and one that's pure. Which one would you choose?

I would counsel everyone to put their RADAR up above the human habitation level on their boat and know that if you ever get cancer/brain tumor/sterility it at least was not from your boat.

Respectfully,

Chuck

I agree.


First choice, locate it so nobody will be in the beam.


Second choice, locate it to get max distance from the antenna.


Under no circumstances be closer than the published safe distances.

 

[OldDan1943]

Soooo, what's inside the dome?
Is there a rotating antenna?

 

[Oldsarge]

Some Radars Furuno (1715) for instance can be adjusted for a few degrees of non transmission at the rear as it rotates.You loose that area of detection but unless something or someone like the Coast Guard is gaining on you it doesn't matter much.
The reason I mentioned the CG is that they actually did that to me once. The other thing is that Radars are line of sight and the closer you are to the water the less distance you will be able to detect other vessels or landmarks. You loose a lot of range.

 

[AlaskaProf]

I'm probably missing something, but how does a CG warning about an open mike reach the violator? BTW, we also have a Point No Point in Stratford, CT.

https://portal.ct.gov/-/media/DEEP/gis/coastalaccessmaps/CoastalAccessSite330.pdf

In short, it doesn't reach the offender. Anytime you key your transmitter, it turns off your receiver. "Attention all aircraft, (vessels, stations, etc.) check your mikes..." is wasted bandwidth and reveals the lack of sophistication of the person tranmitting. Do this in an air traffic facility (Yes, it happens every day.) and you will become the target of derision from your co-workers.


[edit] Oop, I see everyone else has jumped on this



BTW, the same is true for your radar. After each transmission, it shuts down and listens for the returning pulse. If you look in the specs for your radar you will find the Pulse Repitition Frequency.


Somewhere above there is discussion of a transmitting antenna and an offset receiving antenna, but in my experience, there is only one antenna (or wave guide) alternately sending and listening. (Yeah, I know there are four wave guides in the pic, but that is another story.)

 

[backinblue]

In short, it doesn't reach the offender. Anytime you key your transmitter, it turns off your receiver. "Attention all aircraft, (vessels, stations, etc.) check your mikes..." is wasted bandwidth and reveals the lack of sophistication of the person tranmitting. Do this in an air traffic facility (Yes, it happens every day.) and you will become the target of derision from your co-workers.

Thanks! I thought it was just me, but I couldn't figure out the purpose of the warning if the offender never hears it. The warning makes sense if the keying stops for a few minutes in case they are unaware of a problem or someone playing with the radio and they didn't know.

 

[Oldsarge]

Yes, most commercial Radars have a rotating radiator inside the dome. The Furuno 1715 that I have varies the speed of rotation depending upon what range you are set at. The transmitted signal goes out sort of like a water hose that you are spinning around and even at the speed of light light, which is what the signal is transmitted at, it takes a little time for the signal to go out and be echoed back to the receiver and displayed. Also the Radar equipment has inherent electronic delays.

 

[Oldsarge]

Yes, I went through an eight month course in aircraft Radar in the USAF and then worked with a high power long range search Radar. You can get cooked like in a microwave oven if you are a short distance away in front of the antenna when it is radiating on high power. There was a big danger sign near the Radar warning people to stay away from the antenna.

 

[AlaskaProf]

The Furuno 1715 that I have varies the speed of rotation depending upon what range you are set at.

Interesting, not what I would expect. As you can tell from my posts, I actually know very little about the specifics of my Raymarine C80, and I infer a lot from my experience with "big" radar, (admittedly, a risky ploy) which is always emitting at a fixed speed and power while individual displays can be set for a variety of ranges.



i.e. If I were working Seattle South Satellite, I might be looking at 30 miles centered at Tacoma Narrows, but the antenna is still rotating at 15 rpm at a range of 55 miles from SEA-TAC, emitting about a megawatt a couple hundred times per second.

 

[Slider70]

I am no expert so take this for what it is worth.

In 1986 I had a teck working on my boat radar. The boat was a commercial salmon troller. He had worked the DEW line for many years for the military. He strongly suggested that I glass in a sheet of bronze screen over top my wheel house between me and the radar, grounding the screen to my bonding system to protect me from the rays. He said he had work mates that had been lost to brain tumors, and more with cataracts, that were believed to be associated with exposure to these rays.

Obviously those radars were/are far more powerful than ours. But I took his advice and did this on my vessel. On two future commercial vessels I purchased it had already been done. I past this information on to all of my commercial fishing friends. I think most ignored my advice.

Unfortunately, my two best friends in the business are now both dead from brain tumors. All of us commercial fishers spent weeks each year fishing with the radar on. And, likely those radars of the old days were more powerful that the ones we use today?

My two friends brain tumors and those of two others fellows I fished with, may have had nothing to do with their radars but for me just moving the unit away from my head or shielding is a small price to pay for my ease. And yes I know many things are likely to kill me other than my radar but I like to reduce as many risks as I reasonable can.