Rookie Radar Question

So...I have very little practical experience with radar, but I'm curious about something. If you mount your radar on the front of the bridge, as in the picture below, do you get any return from behind you, or will the radar only "see" the 180 degrees in front of the boat ? I can't imagine the fly bridge doesn't interfere with your radar, but it seems odd to spend all that money on a radar system, and mount it in such a way that you can't see all around you. Thanks.

You will get nothing meaningful from behind.

At that location, the flybridge will be a good place to be irradiated.

AT that location, Mark is right. You would be irradiated by the older radars, which is not a good thing. Radar energy is what cooks your food in a microwave. It cooks everything in its path. Arms, legs, brains, stomachs, etc.


The new radars are at a much lower energy level and I have read that they will not cook you the way the old ones do. I'm not sure I'd trust my body to that, but they say it's safe.


Either way, a radar mounted in that position would not give a return to the rear.

twistedtree said:

You will get nothing meaningful from behind.

Click to expand...

I would respectively disagree. I have had ships behind me going faster than me in the fog.

markpierce said:

At that location, the flybridge will be a good place to be irradiated.

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I agree with mark and GFC. Need to mount it above your top.

Thanks...it seems like a fairly common place to put the radar, based on a lot of pictures on Yachtworld and so on, so I thought maybe I was missing something. Thanks.

The higher the radar antenna is, the further it sees. It also helps with sea clutter in rough water.

A previous boat had it mounted there when we bought it. We had a blind spot about 30 to 40 degrees wide to the rear. I later installed a mast and moved the radar up on it.

Lousy location for any kind of radar, but broadband puts out very little energy and definitely won't irradiate you. It also doesn't reach very far, best useful range of only a couple of miles. The radar that WILL irradiate you has a much more useful range for most purposes, and the higher you mount it the better it's range. It is recommended that broadband be mounted very low on your vessel so it will illuminate things very close by, you can see the space between boats and their docks with broadband. You still need 360 degree visibility no matter the radar type...

I can't tell from your picture exactly how high the antenna is, or where the helm is located. Radars *will* see through the thin fiberglass of the bridge but at the cost of a degraded image. It wont see through wiring or humans. The radar wont harm you where it is and I wouldn't count on it to paint targets behind you behind you. It will do a fine job (well,as good as Furuno's little 2,2kW unit has ever done) of showing targets & storms ahead of and beside you.

Originally Posted by twistedtree View Post

You will get nothing meaningful from behind.

Alaskan Sea-Duction said:

I would respectively disagree. I have had ships behind me going faster than me in the fog.

.

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The key word is meaningful.

When a radar signal gets degraded by passing in two directions through materials, what it "sees" and what it displays may vary with many other environmental conditions.

So one day, you may see ships behind you; other days you may not.

Happens all the time with rain. Even humidity will affect the return, as well as how the radar sensitivity is set up in terms of filters and gain.

many RADARs mounted like that just program a dead zone where it doesnt even transmit in the zone where the bridge seating is... so radiation is not sn issue.

while knowing what is behind you is nice, for many cruisers who chose to travel in daylight and fair weather. a dead zone aft is no big deal.

if you cant live with thst, mount it elsewhere but that usually is inconvenient so people fall back to this option .

My older Raymarine is in a similar position (you can see it clearly in the beginning of my Slow Lane video below). I "see" images from behind me all the time.

I've even seen newer boats with the radar in a similar position. I highly doubt manufacturers would put it there if it was hazardous to your health. Please don't dramatize it so much guys. Drama queens.

Alaskan Sea-Duction said:

I would respectively disagree. I have had ships behind me going faster than me in the fog.

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You gotta love language.... What I meant was that the radar would not provide any meaningful detection of things behind the boat, not that there isn't anything meaningful back there to care about.

Wxx3 said:

Originally Posted by twistedtree View Post

You will get nothing meaningful from behind.

The key word is meaningful.

When a radar signal gets degraded by passing in two directions through materials, what it "sees" and what it displays may vary with many other environmental conditions.

So one day, you may see ships behind you; other days you may not.

Happens all the time with rain. Even humidity will affect the return, as well as how the radar sensitivity is set up in terms of filters and gain.

Click to expand...

twistedtree said:

You gotta love language.... What I meant was that the radar would not provide any meaningful detection of things behind the boat, not that there isn't anything meaningful back there to care about.

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So if you take the OP's picture, I would agree you are not going to get any useful info from behind when mounted in such a position.

However if the radar is mounted above you should get good information aft of the boat.

I understand that most boaters are only looking forward and concerned only with what is in front of them but should be aware of 360 degrees around them.

Keysdisease said:

Radio Frequency
Radiation Hazard​

The radar antenna emits electromagnetic
radio frequency (RF) energy which can be
harmful, particularly to your eyes. Never
look directly into the antenna aperture from
a close distance while the radar is in
operation or expose yourself to the transmitting
antenna at a close distance.
Distances at which RF radiation levels of
100 and 10 W/m​

​

​

​

2 exist are given in the
table below.​

Note:​

​

​

​

​

If the antenna unit is installed at a
close distance in front of the wheel house,
your administration may require halt of
transmission within a certain sector of
antenna revolution. This is possible - Ask
your FURUNO representative or dealer to​

provide this feature.

https://www.furunousa.com/-/media/s...18x4c_19x4c_gp1920c_installation_manual_k.pdf

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Keys, that's a lovely copy & paste from Furuno but his 1600 series won't do transmit blanking sectors and anyway, it is about the same power as a large microwave oven. If he were to unscrew the lid, grab the rotator & stare into it while transmitting on hi power, at maybe 6" no less, he would probably do damage to his eyes. Otherwise , there really isn't any need to be too upset.
I know radars pretty well & BTW, I had the exact same setup on my Bertram years ago (I later replaced the Furuno with a 4kW antenna...twice the power... in the same location) & used that radar a lot & my retinas are still intact!

That also is what the Furuno tech told us at the annual update traning.... your head would have to be inside the dome or the swing of up to a 4kw array.

I wasn't looking to start a debate about the safety of being close to the transmitter, as I know there are too many variables there for general statements to apply to everyone.

I would think that when you cruise at 7-8 knots, what's coming up behind you could be pretty important.

Thanks again.

Just do a clearing turn if you think something could be behind you.

Hi,
I'd be a little leery of a clearing turn in the fog with unknown traffic at a unknown speed behind me. On the subject of radar safe distance, all I remember is the NATOPS for the P3 aircraft warned against energizing the old APS80 on the ground if you were parked closer than 75' to a fuel truck. Of course this was a 150 kw radar. Seems to me the less exposure, the better.
Regards,
Roger

A clearing turn doesnt need to amount to much more than a course change....but.....

If your scared of changing courses because someone might be behind you and hit you, then yes, mount the radar differently.

Even then, seeing them on radar may not change the outcome.

Lepke said:

The higher the radar antenna is, the further it sees. It also helps with sea clutter in rough water.

Click to expand...

Actually, since the distance to horizon is shorter the lower the radar is, and since ships especially, but also even smaller boats, are high enough to be seen for some distance (and to return a radar signal) even when beyond the horizon, the sea clutter problem is less pronounced when the radar is low. Also, choppy seas present a better reflective surface (ie, more clutter) to a higher radar, than to a lower one, because the angle of attack is greater.

And too high negates close in work.....

Which some do and some don't care about.....

I like mine on the mast as it provides good 360* coverage. The aft view is so good that I can see my wake behind me and targets several miles aft (never really measured it, though). Aside from cost, the negative is that the mast requires a taller covered slip without a tip-down feature.

Mine doesn't tip down, but I don't mind. Seems like it'd be a hassle having to tip it down and up each time I come and go. I have forgotten my VHF comm antennas enough times to know that I could not be trusted to always remember to tip down the radar mast.

As noted, the newer solid circuit radars are not a health hazard. Same exposure as a cell phone.

The statement that solid states only see a few miles is not accurate. I had an open array, and then solid state on past two boats and the newer solid state was much better than the higher juice open array. Yes, nothing beats a high energy open array for the long view, but the newer solid systems are hard to beat for recreational boaters.

From what I have been reading, all recreational radars will one day be SS. Don’t shoot the messenger.

Re the location of the one in the picture, Agree, see quite a few boats out there with that configuration. I want to be able see at least the aft quarters on the Display.

My radar is located on a high mast. Nevertheless, it's worthwhile using eyeballs to see what's occurring to the stern, particularly in a slow boat.

I wonder if ours works as well as it should as it does point skyward.
Radar follows funnel line
Funnel follows roof line and it is swept up.

I rarely us it as it is not as spectacular as I imagine they should be.

You could put a wedge in there (made for specifically for radars) but not sure that would be enough. Looks to be off plane by quite a bit.

I milled a wedge out of 1.5” starboard to raise the front of the scanner. It was pointed downward a significant amount. I suppose the strut was made for a planning hull that has more bow rise than we do when we run at 10 mph. Before and after photos below.