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Old 03-18-2018, 09:29 PM   #1
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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.
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Old 03-18-2018, 10:31 PM   #2
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You will get nothing meaningful from behind.
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Old 03-18-2018, 10:37 PM   #3
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At that location, the flybridge will be a good place to be irradiated.
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Old 03-18-2018, 10:45 PM   #4
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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.
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Old 03-18-2018, 11:14 PM   #5
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Quote:
Originally Posted by twistedtree View Post
You will get nothing meaningful from behind.
I would respectively disagree. I have had ships behind me going faster than me in the fog.

Quote:
Originally Posted by markpierce View Post
At that location, the flybridge will be a good place to be irradiated.
I agree with mark and GFC. Need to mount it above your top.
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Old 03-18-2018, 11:45 PM   #6
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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.
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Old 03-19-2018, 12:51 AM   #7
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The higher the radar antenna is, the further it sees. It also helps with sea clutter in rough water.
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Old 03-19-2018, 02:19 AM   #8
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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.
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Old 03-19-2018, 04:06 AM   #9
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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...
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Old 03-19-2018, 04:25 AM   #10
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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.
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Old 03-19-2018, 04:39 AM   #11
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Originally Posted by twistedtree View Post

You will get nothing meaningful from behind.
Quote:
Originally Posted by Alaskan Sea-Duction View Post
I would respectively disagree. I have had ships behind me going faster than me in the fog.

.
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.
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Old 03-19-2018, 06:14 AM   #12
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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 .
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Old 03-19-2018, 06:45 AM   #13
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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.
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Old 03-19-2018, 09:15 AM   #14
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Quote:
Originally Posted by Alaskan Sea-Duction View Post
I would respectively disagree. I have had ships behind me going faster than me in the fog.

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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Old 03-19-2018, 10:31 AM   #15
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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/si...n_manual_k.pdf


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Old 03-19-2018, 10:53 AM   #16
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Quote:
Originally Posted by Wxx3 View Post
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.
Quote:
Originally Posted by twistedtree View Post
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.
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.
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Old 03-19-2018, 11:08 AM   #17
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Quote:
Originally Posted by Keysdisease View Post
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/si...n_manual_k.pdf


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!
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Old 03-19-2018, 12:01 PM   #18
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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.
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Old 03-19-2018, 01:41 PM   #19
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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.
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Old 03-19-2018, 01:49 PM   #20
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Just do a clearing turn if you think something could be behind you.
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