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Old 14-03-2011, 16:33   #1
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Radar Reflectors

i was just curious if someone could tell me a good radar reflector to buy. however, isn't it just rquiring flat metal surfaces for wave reflection? if so then couldn't you just make one for about $5? any thoughts
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Old 14-03-2011, 16:42   #2
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Re: radar reflectors

Certainly. It would be a great 7th/8th-grade, metal-shop project. (Do they still teach that stuff in intermediate school?)
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Old 14-03-2011, 16:43   #3
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Re: radar reflectors

If you are looking for economy, the Davis reflector has a very good reputation. There are a few others but much more expensive.

Rich

If you search at Amazon you will find a variety that seem to average around $50.
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Old 14-03-2011, 17:13   #4
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Re: radar reflectors

I posted a number of interesting testing results in this blog entry:
Sail Delmarva: Search results for radar reflector
Go down to the radar reeflector section.

There are some home-made reflectors, some of which were tested and did fine.

But yes, the Davis reflector does seem like the best compromise.
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Old 15-03-2011, 06:51   #5
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Re: Radar Reflectors

Check out this article on homebuilding an interesting reflector design:
Duckworks Magazine - Passive Radar Reflectors

and a follow-up article with more detail on the construction:
Duckworks - Do It Yourself Lifelines and Bow Pulpit

I built one of these using aluminum roof flashing and pop rivets. Total cost: $10, with material left over to build a second one.

We haven't been run down by a freighter yet! (Actually, I have wanted to radio a boat with radar to ask what our boat looks like on their screen, but have not done so yet. So really, I have no idea how well this works -- but it all seems good in theory.)
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Old 15-03-2011, 07:09   #6
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Re: Radar Reflectors

You may want to look at the results of this 2007 radar reflector test commissioned by the UK Marine Accident Investigation Board (.pdf file).

http://www.maib.gov.uk/cms_resources...s%20report.pdf

In a nutshell- none perform as well as promised, but some are better than others. Tri-lens type reflectors fared the best.
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Old 15-03-2011, 07:14   #7
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Re: Radar Reflectors

Also good, with lots of data, is The Radar Reflector Site . Phil is an old colleague and really knows his stuff.
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Old 15-03-2011, 07:30   #8
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Re: Radar Reflectors

it just seems to me that what makes the stealth bomber and the stealth chrysler virtually undetectable is the fact they have no flat spots that return signal.. i was thinking if a guy uses 1/16 stainless about 12x12 and rigged it atop the mast, theoretically it should work well.
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Old 15-03-2011, 08:35   #9
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Re: Radar Reflectors

A piece of flat metal might work well for the two directions its facing but not for the directions the 1/16 in was facing. You need something that will reflect in a 360 degree pattern.

Rich
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Old 15-03-2011, 09:32   #10
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Re: Radar Reflectors

Someone, I think it was Ocean Navigator did a pretty in depth study of radar reflectors about 5 years ago. They tested the major designs at several distances and at various 'angles of heel', including to the side (L-R) and toward the radar (front to back). They also tested them all in the various angles (ie from bow to stern in an arc) to see if some were better in a specific horizontal angle or specific orientation. The resulting diagrams of reflectivity strength were really neat showing how some reflectors worked exceptionally well in a very narrow range but quickly lost the ability reflect well outside of that range. The overall best in the ranges that a sailboat would heel (up to about 30-45 Degrees) was the tri-lense. It reflected well in all horizontal orientations and had the widest 'strong' range of the group.

The Echo Master by Davis also worked great but only in the 'catch rain' position which it is usually not mounted. It also diminished effectiveness drastically after a heel of about 15 degrees if I remember.

There was one other that had a really strong return in a narrow horizontal band, but diminished severely outside that. Wish I could remember what it was.

I scan good articles when I find them, but lost that one before I got my scanner.
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Old 15-03-2011, 09:33   #11
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Re: Radar Reflectors

The medium-sized BBQ mounted on my pushpit seems to do a better job reflecting radar than any of the commercial radar reflectors available.

And it does a better job grilling a steak.
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Old 15-03-2011, 09:51   #12
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Re: Radar Reflectors

Look at the design in the Duckworks link above. It's a very interesting shape and should provide better reflection around 360 degrees, and various angles of heel. If I had any metal shop ability, I would produce them commercially.
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Old 15-03-2011, 10:01   #13
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Re: Radar Reflectors

I have Firdell Blipper Radar reflector which is now discontinued and replaced by the EchoMax Radar Reflector. At $220 it is pretty expensive. There is also a Mobri reflector but I'm not to sure how well they work although they are quite small and usually mount on the shroud just above the spreader. They claim to be excellent.

EchoMax:
EchoMax 230BR Radar Reflector

Mobri:
MOBRI Radar Reflector

As you can see, a properly mounted Davis is pretty economical by comparison.

Rich
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Old 15-03-2011, 10:09   #14
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Re: Radar Reflectors

Quote:
Originally Posted by Bash View Post
The medium-sized BBQ mounted on my pushpit seems to do a better job reflecting radar than any of the commercial radar reflectors available.

And it does a better job grilling a steak.
Bash

How do you work with a BBQ mounted 4 meters above the waterline?

Quote:
PERFORMANCE
3.1 The radar reflector should have a žStated Performance LevelÓ measured in square metres
radar cross section (m
2
RCS) of at least 7.5 m
2
in X-band and 0.5 m
2
in S-band mounted at a
minimum height of 4 m above water level.
Lots of freeboard?
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Old 15-03-2011, 10:25   #15
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Re: Radar Reflectors

Have seen some of the data on various kinds of radar reflectors and have decided that the standard Davis unit is best. Some of the newer mast mounted units look really nice and require no hoisting, maintenance BUT they seem to have poor performance. Watching the signals I receive when in fog, I can say that sailboats without reflectors up are nearly invisible to the radar. There must be something about the rigging that makes sailboats harder to see than powerboats. Even though it a is a major PAIN, having the aluminum ball rattling around in the rigging, I make sure it is up at all times and have semi-permanently strung it up with Dyneema just below the spreaders.
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