Radar Dome Locations

I am sort of hi-jacking this from the thread on boating history, but it got me thinking.* My radar is mounted on a fiberlglass mast, typical of many trawlers.* The bimini frame is in directly in from of the dome.* Common sense would say that the frame diminishes some of the performance of the radar.* Should I relocate the radar?

If the portion of the frame in front of the dome is vertical I probably wouldn't worry about it as the portion of the blocked signal will be very small. But I assume the portion of the bimini frame in front of the antenna is horizontal which I think could definitely interfere with the signal in some way.

But you don't need to relocate the radome. Just raise it enough on its mount so the sweep clears the bimini frame. I don't know where you live, but here in the Seattle area there is a company called PYI who specializes in things like radar mounts, risers, arches,and masts. Their website is http://www.pyiinc.com/ . When we replaced the old radar that came on our boat with a new Furuno NavNet last year we had PYI make us an adapter riser to center the Furuno radome (which is offset forward) on our existing mount. They built it to my design and dimensions, but I believe they carry stock size risers as well.

If you live anywhere near a reasonably popular boating area, I'm sure there are local companies similar to PYI who do this sort of work.

Just make sure your eyeballs and testicals are not within a 15 or 20 deg up or down area in front of the radar.

You could loose your eyesight or your future kids cold have 3 eyes or be Democrats.

FF

Marin, I sure hope you don't pilot from your fly bridge when the radar's on. From your picture, it looks about testicle height! Or maybe eye level if you're sitting down.

First of all, the emissions from a modern recreational radar are so weak that the folks who work with this stuff professionally tell me that the only way you can damage yourself is to literally put your head up against the radome when it's on and keep it there for days and days and days. The measured signal strength is such that sitting or standing four or five feet away from this type of radar antenna will do virtually nothing (this is NOT true of more powerful military or commercial units). The effect will be even less nothing if the exposure is infrequent, as it would be on a typical recreational boat that gets used relatively little over the course of a year.

That said, everyone I've talked to about this subject, from people at Furuno to people at Boeing to the marine electronics sales and repair shops we use, say "better safe than sorry" since every person is different and reacts to their environment differently. So it's not smart to position yourself in the path of a radar transmission regardless of how weak and harmless the signal is.

With regards to our own boat, a flying bridge face radar mount was quite common in the 60s and 70s when a lot of boats like ours had solid wood masts (or no masts). Since electronics back then were pretty heavy and bulky--- as were their connecting cables---- it was assumed that the navigation equipment would be at the lower helm station out of the weather, so that's where the boat would be conned from when the visibility or weather was bad. The flying bridge mount also makes connecting the antenna to the display unit extremely easy--- in our case with the retractable overhead display mount, the distance from the radome to the display unit is about four feet or in a straight, unobsructed line under the flying bridge consol.

The introduction of hollow aluminum masts and the miniaturizing of components like the radar antenna cable made it possible to easily mount an antenna on the mast and run the cable down and forward to the display. This is BY FAR a preferable antenna setup than the flying bridge mount for a whole lot of opeational reasons. I would never recommend a flying bridge face mount for a radar antenna--- the very few advantages are far outweighed by the disadvantages.

As I have stated in other posts, we never run our boat from the flying bridge regardless of the weather for a whole lot of reasons. So even if the transmission signal from the radar was potentially damaging, we're never going to be in a position to be in its path anyway. On the rare occasions when we have other people on the boat, we inform them of the antenna's position and make sure that nobody goes up to the flying bridge when the unit is transmitting. This isn't likely anyway in bad weather (which is the norm up here). If someone does want to go up we simply put the radar in standby while they're up there. Again, the chances the beam would affect them in any way is in theory zero but since there aren't any guarantees, better safe than sorry.

We would like to reposition the antenna to the mast although our reasons have nothing to do with health issues. But right now this project is a long ways down the "to'do" list.

-- Edited by Marin at 13:29, 2008-03-27

Good for you! Of course, you could have just said "we don't".

True enough. But you'd be surprised by how many people when they see the picture of our boat or the boat itself ask me if mounting a radar antenna on the face of the flying bridge is something we would recommend. So I thought a more detailed answer here might forestall yet another inquiry

Thank you Marin for the long answer, we are considering installing a new radar as the old huge crt unit has spat the dummy. You input helps alay some fears, and confirms pretty much what I was thinking.
Cheers

Other thing to remember is that radar is microwave radiation, not atomic decay radiation. So any damage that it could possibly do is through heating, not what you'd typically call "radiation exposure."

It's basically a microwave oven with a very directed beam. If you were to put your head directly in front of a stationary antenna, it could possibly heat your brain and eyes up to the point that they would be damaged (I think 108 degrees F or so).

If you're really paranoid about it, get yourself a nice 3-4 pound ham and set it - in cool weather and out of the sun - where you'd be sitting in the beam. Then run the radar for an hour or so and stick a thermometer into the ham. If it's not warm, you've got no problem.

(on second thought, if you had a brain, would you even own a boat??? )

Unless you have air draft problems it would still be better to mount your radar higher on a mast or mount just so that you could maximise the radars capability.
There is no point in limiting its potential as it is a very important navigational aid.
Having it down low is a bit like anchoring and leaving half your anchor chain in the locker.
Benn

Yes and no. It depends on where you boat and what your radar requirements are. Not long after we got our boat I read an article by a respected "expert" on radar, and he made the point that mounting a radar as high as possible is not always the best idea.

We have a new Furuno radar with a potential range of 36 miles. We are never going to need to see 36 miles with it. In fact, we have yet to set it to a range above six miles other than testing it after its installation. In the waters where we boat, the maze of islands prevent you from seeing much more than five or six miles in any direction most of the time. There are exceptions like the Strait of Georgia, Queen Charlotte Strait, etc, but for the most part the lower ranges is what we use. The ranges we work the most are 0.125 miles to 3 miles.

We boat in the fog if it's foggy and what we DO need to see in our waters are things like crab pot buoys, small local fish boats, etc. With our radar mounted where it is, we see crab pot buoys right up to about 50 feet in front of the boat. Mounting the radar high will extend the distance the radar can see, but it may decrease the ability to see small, low targets close to the boat. So it all depends on what's important.

I don't advocate a flying bridge face radar antenna mount for the reasons I've mentioned earlier. But I wouldn't want our radar at the top of our mast either, as we would miss seeing things we need to see. If the day ever comes that we do move our radome to our mast, we'll mount it just high enough to avoid hitting our heads on it when we come up the steps to the flying bridge.

Someone who boats in open waters and is concerned about seeing shipping traffic with a lot of advance notice would be much more interested seeing as far as they can with their radar.




-- Edited by Marin at 20:29, 2008-03-29