RADAR reflectors

Wandering Sagebrush

Wandering Sagebrush

Free Range Human
I don't know how effective they are, but I wanted one and never bought because i felt the price was too much for what is there.

While poking around my favorite toy store (Fisherman's Marine) in Oregon City, I found a couple of Seadog reflectors for $11.50. The original price was around $30ish. Comparable in WM is $50ish. They are solid aluminum and will break down. There's one left in Oregon City, and maybe some at the Delta Park store.

Steve
 
I have always placed a high priority on radar reflection. I use a medium size tri-lens radar reflector. I have not used other reflection systems, but I know this one works like a champ. It is AMAZING how small of a target even a 30' fiberglass vessel can return for example.

Here is a link for reference, I use the middle size unit:

http://www.tri-lens.com/trilensweb12002002.htm
 
I have one of the mid-sized, aluminum ball types that comes apart. When out in the ocean, I hang it inside the radar arc, but have kept it in the back of the aft dinette cabinet here on the lake. To my surprise, my dockmates say they can see a large echo of my boat for it's size, even with the reflector tucked away.

John
 
I wanted a radar reflector but was put off by the $ for some simple pieces of aluminum. A sheet metal shop here sold me some aluminum and cut it into circles for $2.00 total. I fabricated a reflector from those, bonded the pieces with JBweld and mounted it on the uprights of the radar arch. Pictures are on page 3 of the C-Cakes photo album. Not at all hard to do and I feel a little better. It is not certified by any government agency but the geometry is the same as the commercial ones and physics is physics.
 
Any of the refectors work--some better than others. The foam/foil reflectors seem to work, as do the folding square or aluminum. Even foil over plywood works well. The "Rain catch" position seems to work well.

Having a radar on, may give some interference to a boat with a radar with similar frequency radar, and thus show the boat better. But it does not act as a reflector or intrinsically increase the radar image.
 
When we had our sailboat in Lake Michigan, another boat asked us to check their radar image both with and without their reflector up. Using a 2 kW Raymarine CRT, I could see no difference.

Has anyone tried to scan a boat with and without their reflector (same boat)?

We also had a radar detector. Worthless, because of too many radar signals. Even in the middle of the ocean, we'd get a signal; I assume from satellites. I think that the best radar signal is from the radar on your boat.

Boris
 
colobear said:
I wanted a radar reflector but was put off by the $ for some simple pieces of aluminum. A sheet metal shop here sold me some aluminum and cut it into circles for $2.00 total. I fabricated a reflector from those, bonded the pieces with JBweld and mounted it on the uprights of the radar arch. Pictures are on page 3 of the C-Cakes photo album. Not at all hard to do and I feel a little better. It is not certified by any government agency but the geometry is the same as the commercial ones and physics is physics.
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As far as I know the geometry is fairly critical for this type of reflector. If the angles are a few degrees off 90 degrees, it significantly decreases the reflective profile.
 
I think you are right about the geometry. When I studied radar back in the dark ages we learned that the radar cross section of a target with some kind of reflector was substantially bigger than the same target without a reflector; so I figure even if my home built reflector is a degree or two off my boat will still be a substantially bigger target than without it. When I decided on that construction I used the same geometry as the folding circular reflectors and a true 90 degree square to set my angles and tried to keep to that accuracy. The commercial ones have a loose enough assembly to be off a degree or two and figure if it is good enough for them it will likely be good enough for me. Anyway, I feel better with it there :)
 
I suppose reflectors work, and have read the studies comparing one to the other. Lots of nice numbers, graphs, etc., but what always seems to be lacking are photos of radar screens, showing significant, or even noticable, differences in actual returns. Anyone come across a link to this info?

Whenever we're boating with a group, and someone hangs up one of the disk type reflectors, I make a point of looking at the radar returns, while I change position, range, etc. I've never been able to see an improvement with the reflector up. I do detect differences from one boat to the other, which I attribute to different engine blocks, running gear, etc. But, opening up and deploying a disk reflector has yet to show up on my radar screen.

I haven't done any definitive testing, and perhaps at longer range, or in rougher seas, the reflector would make a difference. I also haven't targeted any of the tri-lens reflectors, which I understand do a better job. My radar is a JRC 1500, which is not top of the line, and perhaps a better set would pick up the differences.

Others have reported improved returns. What's going on?
 
My only experience in a group was about 2-3 years ago when about 6-7 C-Dorys headed across Rosario Channel to Lopez. I was in the front and all where in somewhat of a line spread over about 1/2- 1 mile. It was reported by several others that I "painted" a much bigger picture than others. I have the standard three aluminum disks fitted together to form a sphere. I carry it right under the high arch.

If you are traveling in or through Canadian waters they are required. Although I don't know what they do to enforce it. I guess if you have an incident that gets investigated you better have one.

Anything that makes you look bigger on someone else's radar is a good thing. It is just like driving a car. I don't worry so much about me, it's the other guy I worry about. I want to be seen.
 
David, From discussion with the Canadian "coasties" I believe the requirement to meet their standards (on a number of things including radar reflectors) only kick in after 30 days if my memory is correct.
Enforcement is another issue.

Merv
 
Back in my sailing days I used one of the Davis Instruments foam/aluminum foil reflectors mounted high on a flag halyard right under one of the spreaders. On the Chesapeake I hailed a passing Coast Guard vessel and asked for info on my radar return. They replied that I had a radar signature nearly identical to a large, steel commercial fishing vessel nearby. That surprised the heck out of me, but also made me feel a lot more comfortable as a singlehander.

Nick
"Valkyrie"
 
David,

Here's one for you. If you trailer your boat into Canada from USA via Nexus you will not be given a "magic" number to hang in your window next to the dock. :shock:

What was the first question? :roll:

Merv
 
Anna Leigh said:
If you are traveling in or through Canadian waters they are required. Although I don't know what they do to enforce it. I guess if you have an incident that gets investigated you better have one.
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It's not quite that draconian:

Rule 40 Collision Regulations, Canada Shipping Act 2001 requires a vessel that is less than 20 metres in length or is constructed primarily of non-metallic materials to be equipped with a radar reflector if practicable, unless (i) it operates in limited traffic conditions, daylight, and favourable environmental conditions and where compliance is not essential for the safety of the vessel, or (ii) the small size of the vessel or its operation away from radar navigation makes compliance impracticable.
 
As far as the amount of signature increase a radar reflector shows, let's look at the Davis reflector, which is 11.5" in dia. This is slightly less than 1 sq. ft., MAX. and if it's not pointed with one of the panels perpendicular to the radar beam, can go down to ~1/2 sq. ft.

Now a reflector just reflects energy, it can't increase it beyond what it intercepts, so the MAX reflected radar signal is equal to a 1 sq. ft. target, at the appropriate range. Now compare that with a metal ship that's 50' high by 40' wide by 300' long with lots of metal things sticking out (bridges, etc.)

I do not believe that a small reflector can give the same return signal as a big (or even small) metal ship at the same range. No matter how you look at a ship, one can't get the cross-sectional area down to 1 sq. ft.

That's why I feel the best radar signal is from the radar on your boat. YOU can see the big guys quickly, and can take the appropriate action quickly. I also feel the cheapest radar you can get is the best safety investment for your boat.

Boris
 
journey on said:
As far as the amount of signature increase a radar reflector shows, let's look at the Davis reflector, which is 11.5" in dia. This is slightly less than 1 sq. ft., MAX. and if it's not pointed with one of the panels perpendicular to the radar beam, can go down to ~1/2 sq. ft.

Now a reflector just reflects energy, it can't increase it beyond what it intercepts, so the MAX reflected radar signal is equal to a 1 sq. ft. target, at the appropriate range. Now compare that with a metal ship that's 50' high by 40' wide by 300' long with lots of metal things sticking out (bridges, etc.)

I do not believe that a small reflector can give the same return signal as a big (or even small) metal ship at the same range. No matter how you look at a ship, one can't get the cross-sectional area down to 1 sq. ft.

Boris
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I think you are looking at it too simplistically. Radar reflections are a very complicated matter and have to compete with sea clutter at short ranges. A typical octohedral reflector has an RCS (radar cross section) anywhere from 2 to 10 square metres depending on heel and dips in its profile. It doesn't have to be facing the radar transmitter, the signal is reflected within the corners back to its source. A ship's side, on the other hand has to be directly facing the radar to reflect properly. The ship's signal is more likely to come from all the angled surfaces above the deck line than the hull itself.

The point of a radar reflector may be to provide a minimal consistent reflection that distinguishes a fibreglass boat from sea clutter at short ranges (2-10 miles). Of course, the attentiveness and superior maneuverability of a small boat operator is going to be far more effective in collision avoidance than dependence on the radar operator on a seagoing vessel.
 
journey on":309x2t9z said:
As far as the amount of signature increase a radar reflector shows, let's look at the Davis reflector, which is 11.5" in dia. This is slightly less than 1 sq. ft., MAX. and if it's not pointed with one of the panels perpendicular to the radar beam, can go down to ~1/2 sq. ft.

Now a reflector just reflects energy, it can't increase it beyond what it intercepts, so the MAX reflected radar signal is equal to a 1 sq. ft. target, at the appropriate range. Now compare that with a metal ship that's 50' high by 40' wide by 300' long with lots of metal things sticking out (bridges, etc.)

I do not believe that a small reflector can give the same return signal as a big (or even small) metal ship at the same range. No matter how you look at a ship, one can't get the cross-sectional area down to 1 sq. ft.

That's why I feel the best radar signal is from the radar on your boat. YOU can see the big guys quickly, and can take the appropriate action quickly. I also feel the cheapest radar you can get is the best safety investment for your boat.

Boris
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Boris,

The radar reflectors are so called corner cube reflectors - e.g. when you look into a given 1/8 of the sphere, it's essentially the corner of a cube. Corner cube reflectors have the special property that light (or microwaves) which goes into them comes back out in the same direction from which it entered.
689px-Corner-reflector.svg.png.

This is a much more effective reflector than a similar surface area that is often not directly perpendicular to the signal.
 
Last year my father picked up a radar signal booster. It take a signal that is pointed at it, reads and amplifies it and then sends it back at a higher power there by making you look bigger or more to the point sends a stronger signal that may not other wise be seen at long distance or in big seas. We have not had time of the place to put it to a test yet but its a neat idea.
 
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