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Old 01-11-2012, 12:38 AM   #1
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Locating one's radar antenna

Is there any need for concern where one locates the radar antenna regarding the health of persons aboard?* Consider concerns with cell phones next to brains and that the inventor of the microwave oven got the idea when the chocolate bar melted when he stood in front of a radar antenna.
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Old 01-11-2012, 01:27 AM   #2
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RE: Locating one's radar antenna

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Is there any need for concern where one locates the radar antenna regarding the health of persons aboard?
Assuming we're talking about the typical radar units used by recreational boats like ours, the short answer to your question*(according to the radar people I've talked to) is no.

What I was told when we were replacing the dying radar that came with our boat is that the only way you could do yourself harm from the extremely low power output of recreational boat radar is to hold your head hard against the radome with the unit on and transmitting for a week.

That said, prudence is*the better part of valor.* Why take chances if you don't have to?* So it is smarter to mount the antenna in a position where people on the boat will not be in its transmission beam.

This is not to say that radar cannot be harmful even in short duration exposures.* Boeing made a plane for the USAF, NATO, and Japan*called the AWACS (Airborne Warning and Control Systems).* In essence it is a 707 (later 767)*with a huge rotating radar/IFF antenna on a pylon on top of the fuselage.* While this program was long established by the time I joined the company I did some work in support of it in the 1980s.*

One of the things the AWACS flight crews told me was how cool it was to fly low with the antenna transmitting, bank the airplane, and watch the streetlights down below*come on momentarily as the beam swept across them.

So you probably wouldn't want to put yourself in front of an AWACS antenna when it was transmitting.* Unless you're done having kids :-)
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Old 01-11-2012, 06:30 AM   #3
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RE: Locating one's radar antenna

When I went through radar tech certification at FURUNO I asked the same question.* Got the same answer as Marin.* You would have to have your head so close to the rotating*bar that you would have to duck in and out of it to get any dangerous radiation. So virtually any mount on a boat would be safe.

However unless I could create a "no transmit zone"...I would never mount a radar where a human would stay in it's direct beam for anything more than a moment.
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Old 01-11-2012, 08:30 AM   #4
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RE: Locating one's radar antenna

Why don't you look into Simrad or Lowrance broadband radar?
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Old 01-11-2012, 11:44 AM   #5
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Locating one's radar antenna

I was showing a 75 year old dignified lady through a town home we had for sale. *It was within site of a Bell South microwave tower. *She said that she had heard that they were dangerous. *I said that they were. *She asked how so. *I told her that they could make you sterile. *After a few minutes she turned to me and said, "you were joking. *weren't you".


-- Edited by Moonstruck on Wednesday 11th of January 2012 12:54:07 PM
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Old 01-11-2012, 11:48 AM   #6
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Locating one's radar antenna

Since someone will most likely raise the issue, I'll answer the question before it is asked. Why do some boats have their radar antennas mounted on the face of the flying bridge, which puts anyone sitting on the flying bridge in the path of the transmission beam?

One reason is that on earlier cruisers, like ours, the masts were often of solid wood. And on earlier generation radar units, like the 1980s vintage Raytheon 2600 that was on our boat when we bought it, the cable between the antenna and the display unit was relatively huge. So running this heavy cable down the outside of a wood mast and then the length of the main cabin to the radar display presented some challenges (although it could certainly be done and was done). Mounting the antenna on the face of the flying bridge makes the installation of the radar dirt simple, particularly if, as in our case, the radar display unit is mounted on or in the overhead of the main cabin. The distance from our radar antenna to the display unit is about five feet in an almost-straight line. So almost all of the long connection cable that came with our Furuno is coiled up neatly under the flying bridge console (it was explained to me that you cannot simply cut a radar cable to a convenient length at will--- the length of the cable is "tuned" to the radar unit.)

Also, back in the day, radar equipment tended to be pretty bulky and heavy. And repeater displays, at least for recreational-type radars, were not available. So the equipment tended to be mounted inside the boat, where the reasoning was the helmsman would be steering from anyway in inclement weather.

On our boat we run the radar all the time when we're underway. However, if it's a nice day and one of us or guests want to ride up on the flying bridge we turn the radar off. If we need the radar, we simply tell guests that the cannot go up to the flying bridge. While the transmission signal will not be harmful to anyone sitting on the flying bridge for the length of time they would be sitting there, we nevertheless take the position that no exposure is preferable to even a tiny bit of exposure to a very weak, virtually harmless signal.

At the very bottom of our lengthy to-do list is "Move radar antenna to mast." Whether we ever actually do it remains to be seen--- it would involve a fair amount of work. But the reason we would do this is not for health reasons or to see farther. The upper helm wheel, throttle and shifter mechanisms, steering cable raceway, and other odds and ends of hardware are behind the antenna. While the transmission and return will go through fiberglass (to a degree) they won't through metal. So we have a wedge-shaped blind spot directly behind us. Something big like a Washington State ferry will show up back there, but not smaller power and sail boats.

A lower antenna mounting like ours does offer some advantages in seeing things in the water close to the boat. And up here, with all the overlapping islands, we never run the radar on more than a six mile range because we usually cant see any farther than that anyway. Usually we run on three miles down to an eighth of a mile depending on where we are.* So a higher mast mount would not gain us anything in range that we need or could even use most of the time.

But if one was contemplating the installation of a radar on a boat that didn't have one, I would never recommend a flying bridge face position for the antenna. The advantages of a mast or radar arch position outweigh the couple of advantages of a flying bridge mount.

The only production boat I know of that still uses a flying bridge face mount is the Camano Troll. I have no idea why they do this as it makes no sense to me. The Camano doesn't have a mast and boom arrangement, but a radar arch would be an easy way to go.


-- Edited by Marin on Wednesday 11th of January 2012 12:52:06 PM
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Old 01-11-2012, 08:10 PM   #7
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RE: Locating one's radar antenna

Don that is cute!

Mark, why risk boiling your eyeballs?* Plus having it higher maximizes your range, I believe...
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Old 01-11-2012, 08:13 PM   #8
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RE: Locating one's radar antenna

Jennifer, I think I'm "covered."
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Old 01-11-2012, 08:19 PM   #9
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RE: Locating one's radar antenna

Despite the theory being discussed here, I am not done having kids so I'll never mount or operate one less then 7' above any place I could reguarly stand...or 9" above my head. I often feel bad for the guys handling lines on the travel lift pier when I pull into the pit and forget that the radar is still running......
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Old 01-11-2012, 08:51 PM   #10
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RE: Locating one's radar antenna

My vote would be to have the unit mounted high enough that no person would be subjected to the RF energy transmitted by the unit. My original training was in Air Traffic Control Radar...portable yet powerful enough to reach out quite a few miles. Later I worked with Artillery Radar that had a limited effective range of about 10,000 meters, then with Infantry Radar with an effective range of 10,000 meters as well.

I can pretty well guarantee you, unless you are wearing a lead helmet....and you are exposed for more than a few minutes to RF energy...you will suffer intense headaches, and possible RF burns.

When I was on the Cambodian border in the Delta....I was operating the AN/TPS-5A Infantry radar....with the 10,000 meter range....It stood on a tripod about 3 feet high. We had several of the locals come up and stand right in front of it while it was in operation...and even though we told them not to do it...they did....and the following couple of days they went through hell, and no one else was ever that curious again.

I'm sure there will be rebuttals....but in this case I would be sure to err on the side of caution.
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Old 01-11-2012, 08:58 PM   #11
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RE: Locating one's radar antenna

Quote:
Pineapple Girl wrote:
*Plus having it higher maximizes your range, I believe...
*Precisely. *The closer to the surface of the water it is mounted, the closer the effective horizon is and the shorter the range. *A 24 mile radar mounted at the surface and aimed level cannot see much more than 7 to 7.5 miles, unless the spotted object is taller than the horizon. *

*

I can't remember the equation, but there is one that gives the rule of thumb for distance from the surface to the "horizon".
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Old 01-11-2012, 09:01 PM   #12
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RE: Locating one's radar antenna

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JAT wrote:
I'm sure there will be rebuttals....but in this case I would be sure to err on the side of caution.
*Yes.* Big difference between the radar units you are talking about and today's recreational boating radar units.* ATC radar puts major*interference into a* professional video camera from quite a*distance away.* Up to a mile.**That same*video camera held right next to the Furuno radome on our boat sees no interference at all.
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Old 01-11-2012, 09:08 PM   #13
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Locating one's radar antenna

Quote:
JAT wrote:
*Precisely. *The closer to the surface of the water it is mounted, the closer the effective horizon is and the shorter the range.
Conversely, the higher a radar antenna is mounted the less it will see items close to the boat.** This is the one advantage of a lower-mounted antenna like the one on our boat.* We have no need to see more than about 6-8 miles in the area we boat so a high antenna and the 36 mile rage of our radar would be of no value to us.*

But the water here*can be littered with crab pot buoys and other stuff.* In calm-ish water these things*will be painted*on our radar right up to*a boat length or*so from the bow.* Very handy when running in fog, which is usually accompanied by calm water.* In fog in areas where crab fishermen regularly work we'll run the radar at a range of 1/8 mile to spot the floats.* Many of them incorporate a big fender washer as part of their lashup so they show up on radar very well.

This is not a reason to mount a radar on the face of the flying bridge-- a mast or arch mount is better for several reasons.* But if one boats in an area with a lot of stuff in the water, particularly crab, shrimp, lobster or net floats, an antenna mounted lower rather than higher on the mast or arch can be very beneficial.


-- Edited by Marin on Wednesday 11th of January 2012 10:11:39 PM
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Old 01-11-2012, 10:05 PM   #14
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RE: Locating one's radar antenna

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Marin wrote:
Conversely, the higher a radar antenna is mounted the less it will see items close to the boat.**
*My antenna is maybe 24 feet above the water, and it shows close objects in the immediate area, such as boats on the opposite side of the pier.
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Old 01-11-2012, 10:23 PM   #15
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Locating one's radar antenna

Quote:
markpierce wrote:Marin wrote:
Conversely, the higher a radar antenna is mounted the less it will see items close to the boat.**
*My antenna is maybe 24 feet above the water, and it shows close objects in the immediate area, such as boats on the opposite side of the pier.

The issue isn't the distance to the target, it's the height and size of the target.* A radar beam*fans out both in width and depth from the antenna.* Close to the antenna it is narrower and not very "thick."* Even so, next-door boats are easy because they are as large as yours*if not more so.* Great big target that sticks up quite a ways above the water.

The test is will the radar see a crab pot buoy, which is about*18 inches long and perhaps six inches in diameter floating in the water a boat length or two in front of*your bow?* That ability is much*more tied to the height of*the antenna off the water.* The higher the antenna, the*more*water surface around your boat will be under the sweep of the transmission beam and thus hidden to the radar.**The ability to see*small things, especially*small things*with long lines hanging down from them, is*nice to be able to do up here in the fog or mist*or at night.* Maybe not so much in SFO bay.

We've even picked up gulls flying past the boat a foot or two off the water and a boat length or so in front of us.* Obviously the bird's passage coincided with the sweep of the radar antenna and I was watching the display at the right moment.

*


-- Edited by Marin on Wednesday 11th of January 2012 11:31:23 PM
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Old 01-12-2012, 06:32 AM   #16
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RE: Locating one's radar antenna

round here...many people "kick" their radar to shoot down 10-15 degrees.* This helps with close aboard objects when going slow and as the bow rises as your speed increases..the beam rises to see objects further out.

As I see it...it's more important on semi-displacement boats because of the drastic change in running*trim. I don't think I'll bother on my trawler because there's not much difference in idle versus cruising spreed trim.

The real ticket is a radar platform adjuster...but just more complication for the average rec boat that costs money, needs fixin or replacing...I thiink I'll just make do
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Old 01-12-2012, 06:40 AM   #17
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RE: Locating one's radar antenna

This is how my radar was on my ex old 34 MAinship. Tilted down slightly as described above. Now this setup I used for 14 years. The radar beam had lasting effects on me...it made be buy a bigger boat.

*
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Old 01-12-2012, 06:46 AM   #18
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RE: Locating one's radar antenna

I have hesitated getting into this discussion since I have no credentials in and only the typical experience of 20-some years using small craft radar. I am in the market for a new radar unit and have been researching the "broadband" units from Simrad. All my information on their units come from their marketing material and their reps so take it for that it's worth.

Conventional radar units use magnetron-generated microwave pulses to produce their signal. These signals are apparently powerful enough (damaging or not, I don't know) to show significant distortion at close range, hence the central sunburst on the display. Some manufacturers suppress or filter this close echo, eliminating short range targets.

The broadband unit uses a continuous lower power (1/10,000 of conventional radar - 5 X less energy than a typical cell phone)) variable frequency tone and ties the echo to that variation in frequency to determine distance to target. They claim a target pick-up as close as 6 ft. from the transmitter and the unit has a close-in 100 ft. range ring. The range of their 4G model is 32 nm.

I've been looking for anything negative on these units, but haven't found it. I'll probably spring for one soon.

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Old 01-12-2012, 07:28 AM   #19
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Locating one's radar antenna

Quote:
dvd wrote:
I have hesitated getting into this discussion since I have no credentials in and only the typical experience of 20-some years using small craft radar. I am in the market for a new radar unit and have been researching the "broadband" units from Simrad. All my information on their units come from their marketing material and their reps so take it for that it's worth.

Conventional radar units use magnetron-generated microwave pulses to produce their signal. These signals are apparently powerful enough (damaging or not, I don't know) to show significant distortion at close range, hence the central sunburst on the display. Some manufacturers suppress or filter this close echo, eliminating short range targets.

The broadband unit uses a continuous lower power (1/10,000 of conventional radar - 5 X less energy than a typical cell phone)) variable frequency tone and ties the echo to that variation in frequency to determine distance to target. They claim a target pick-up as close as 6 ft. from the transmitter and the unit has a close-in 100 ft. range ring. The range of their 4G model is 32 nm.

I've been looking for anything negative on these units, but haven't found it. I'll probably spring for one soon.

dvd
*I too am very interested in the 3G/4G broadband.* I hear the distance performance of the 3G was VERY disappointing past 5 miles or so but the 4G is better...how much better?* No enough feedback from people I trust to give a realistic answer before popping for the extra $600 over 3G.

I like long distance radar...but close in performance wins hands down for me.* I have mixed reports that it's THAT much better...but the "lean" is that it is better and worth buying.

I definitely wouldn't buy*broadband from a radiation safety standpoint.* The radiation from small boat radar compared to most radar*is like using a cell phone as opposed to having your head in a microwave.

*



-- Edited by psneeld on Thursday 12th of January 2012 08:31:06 AM


-- Edited by psneeld on Thursday 12th of January 2012 08:33:18 AM
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Old 01-12-2012, 08:01 AM   #20
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RE: Locating one's radar antenna

There has been some discussion on Panbo's Weblog about Simrad's, Garmin's and Navico's HD radar and some others.* If I was upgrading,*I would probably make the change.* http://panbo.com/
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