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Old 26-11-2019, 08:51   #16
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Re: To reflect or not to reflect

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Originally Posted by a64pilot View Post
A mast really isnít a directional reflector.
A factory made radar reflector (aka corner reflector) is though, thatís how they work.

I doubt that a Cat has much if any larger an RCS than a similar sized mono. itís most likely the metal bits that contribute most to RCS, the lifelines and rigging, mast, Solar panels etc.

But what really hurts us is that we are relatively low to the water and we would easily get lost in ground clutter, we give a return, but itís lost in the clutter.

Years ago late 70ís I believe a motorcycle magazine conducted a test to determine the range at which a Police Radar could determine a motorcycles speed.
What they found out was very confusing at first, some of the little sport bikes could be tracked further than the full dress Harelyís they eventually figured out it was the headlights, the headlights were concentrating the Radar beam and reflecting it back to the Radar and many of the Sportbikes had dual headlights if you took the headlight bucket and re-aimed it way up or down, a motorcycle especially a sport bike was very tough to detect. Back then most Standard Japanese motorcycles headlights had one mount on either side and it was simple to move it so it would point way high or right at the ground.

Now almost if not all sport bikes headlight reflectors are plastic and donít reflect Radar.

I suspect I used the wrong wording.


A mast is like a mirror. The reflection leaves at the angle of incidence, not in the direction from which it came, unless the angle is exactly 90 degrees. Tilt the mirror at all, and the return goes into space.



A corner reflector returns the reflection in the direction from which it came.
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Old 26-11-2019, 10:59   #17
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Re: To reflect or not to reflect

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I suspect I used the wrong wording.
A corner reflector returns the reflection in the direction from which it came.

I donít believe so, I believe it still has the be aimed or pointed correctly, just like the motorcycle headlight bucket if not correctly oriented the reflected energy isnít reflected back

https://en.m.wikipedia.org/wiki/Corner_reflector
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Old 26-11-2019, 11:39   #18
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Re: To reflect or not to reflect

I can recall hearing a Mearsk Capt. giving a guy down the road for not having a reflector.
She was specific on every aspect relating to why he was lucky he wasn't run over.
Take it for what it is worth.
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Old 26-11-2019, 11:54   #19
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Re: To reflect or not to reflect

All I know is most any boat will show on the radar until you reduce the sea clutter by adjusting in messy seas. Then you may not get a signal back. Not sure what the answer is, but have often wondered if the hanging units really do much, although I've always had one.
Also sea bouys reflect real well on radar, and they seem to have similar reflectors atop them like the aluminum ones in your rigging. A bit bigger than most I guess and steel.
isn't there an active radar signal system?
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Old 26-11-2019, 12:20   #20
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Re: To reflect or not to reflect

I have been picked up on one of those roadside radar trailers while riding an aerodynamic carbon frame bicycle. Carbon handlebars, wheels and seatpost. Barely any metal to the thing... Was it picking up the spokes/brake handles/chain and sprockets?


I use a Davis reflector at the spreaders and have a WW2 surplus reflector in the ditch bag.
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Old 26-11-2019, 14:56   #21
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Re: To reflect or not to reflect

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I have been picked up on one of those roadside radar trailers while riding an aerodynamic carbon frame bicycle. Carbon handlebars, wheels and seatpost. Barely any metal to the thing... Was it picking up the spokes/brake handles/chain and sprockets?


I use a Davis reflector at the spreaders and have a WW2 surplus reflector in the ditch bag.
You were probably not that far from the trailer and carbon is probably a good reflector. If I understand the trailer, I haven't seen one in years. You are going whatever MPH. My brother used a radar gun to clock his kid on a jet ski, again not a great distance. I haven't the slightest of what it reflected off?
I'm with you on a Davis reflector from the spreader. I have seen crumpled up aluminum foil in a 2 ltr. soda bottle used?
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Old 26-11-2019, 15:09   #22
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Re: To reflect or not to reflect

The point of a corner reflector is to return the radar signal in exactly its direction of incidence. The problem with them is that they have peaks and valleys in the reflection pattern. But itís still a matter of getting the maximum radar cross section: area and proper construction are the keys.

The U.K. commissioned an elaborate set of tests after a small boat was run down in the Channel during the 90s. If I remember correctly, the Davis was better than all but some very expensive Luneberg lense designs.
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Old 26-11-2019, 15:23   #23
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To reflect or not to reflect

Quote:
Originally Posted by Cheechako View Post
All I know is most any boat will show on the radar until you reduce the sea clutter by adjusting in messy seas. Then you may not get a signal back. Not sure what the answer is, but have often wondered if the hanging units really do much, although I've always had one.

Also sea bouys reflect real well on radar, and they seem to have similar reflectors atop them like the aluminum ones in your rigging. A bit bigger than most I guess and steel.

isn't there an active radar signal system?


We see bouys etc sometimes because we donít have a look down angle on them or not much depending on where your Radar is mounted, they have clear sky as a background and they stand out against that as there is no returns from clear sky.

Reflectors mounted on our little boats, they are obscured by the ground clutter of the ocean, if there is any kind of seas, from a high mounted ship Radar.

In Germany my unit would war game against our German sister unit which was a Roland missile system. If they set up on top of a hill, they had great range, but I could get them, by staying real low and staying in the ground clutter.
But if they were in a valley, they had much less range of course but if I tried to get them, I would almost always be skylined (think old western movie when you could see the Indians creeping across the top of the hill) and they would get me. One time I even dismounted my Lt. and had him crawl up and find the Roland in Binoís. Then he came back and I ground taxied under power lines and the Roland got me.

The ship is that Roland on a hill trying to break out your boat and reflector in the sea clutter, he canít resolve you with all those returns from the sea, likely.
Now your Radar has him skylined, plus of course heís huge with huge RCS, our much less sophisticated Radar will see him.

Yes there is an active reflector, and that has great promise, but I donít have any experience with it t say itís a good one or not.
I keep saying this but itís true, think about a dark night and a ship has a searchlight that turns around in circles looking for other vessels, yes you can put a small piece of reflective tape on your boat, it canít hurt, but if you really want to ensure your seen, you will have your own light, a flashing one would be good. Thatís in effect a transponder.
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Old 26-11-2019, 15:27   #24
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Re: To reflect or not to reflect

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Originally Posted by Bycrick View Post
The point of a corner reflector is to return the radar signal in exactly its direction of incidence. The problem with them is that they have peaks and valleys in the reflection pattern. But itís still a matter of getting the maximum radar cross section: area and proper construction are the keys.

The U.K. commissioned an elaborate set of tests after a small boat was run down in the Channel during the 90s. If I remember correctly, the Davis was better than all but some very expensive Luneberg lense designs.


Yes Physics is hard to argue against, you can have all kind of things and set up your own tests for marketing etc, but the plain simple corner reflector is tough to beat, itís why you see them on the sides of runways and why they are on bouyís if the tube reflector was better, Iím sure it would be in bouyís
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Old 26-11-2019, 16:04   #25
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Re: To reflect or not to reflect

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Hi
fit a good ........ active reflector.
This
plus AIS


most recreational sized passive reflectors are better than nothing at all but they are still really really poor - just not enough reflective surface area. There have been a number of decent tets of recreational reflectors - like this one and like this one.
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Old 26-11-2019, 16:10   #26
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Re: To reflect or not to reflect

Sailboats give a rather poor reflection ...i struggle to pick them up at 4 miles in calm weather with a well tuned radar

It is very worthwhile to add a reflector to increase your signature
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Old 26-11-2019, 16:58   #27
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Re: To reflect or not to reflect

I had an active reflector for a while. But I could not use it and my boats radar at the same time, I melt tripping alarms on my radar.

Been a while so I forget details.

But then again both our boats are steel.
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Old 02-12-2019, 11:26   #28
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Re: To reflect or not to reflect

Hello all,
As a fairly recently retired Master Mariner after 40+ years at sea in many varied types of vessels I can categorically state that a properly fitted radar reflector greatly enhances the radar reflection of any (relatively) small craft, especially in rain or sea clutter.
Ciao,
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Old 05-12-2019, 07:28   #29
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Re: To reflect or not to reflect

After reading the replies to this post, about reflections and angles that radar would recognize at different angles. Is extremely informative. Has anyone tried to construct a reflective device in the shape of a disco ball made out of metal?
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Old 05-12-2019, 07:47   #30
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Re: To reflect or not to reflect

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Originally Posted by Bycrick View Post

The U.K. commissioned an elaborate set of tests after a small boat was run down in the Channel during the 90s. If I remember correctly, the Davis was better than all but some very expensive Luneberg lense designs.
You are referring to the report on the sinking of the OUZO.

https://assets.publishing.service.go...ors_report.pdf

Quote:
The following is concluded;
∑ The Sea-Me is a good example of an active reflector (RTE) exceeding the
requirements of the current and future ISO 8729 at heel/elevation angles of up
to 15˚, it is also very small and light. Drawbacks are that it requires power to
operate (which on a yacht is at a premium), it will only operate at X-Band and
will offer no performance at S-Band.
∑ The POLARef shows excellence is possible but at a price, technically it just fails
meet current ISO8729 [1] or its replacement [2]. The main drawbacks are it is
very costly at £2000 and its quite heavy at around 5kg. It is currently used as a
radar measurement standard although it could possibly be re-engineering for
commercial production which could reduce the price.
∑ The Large Tri-Lens performs well especially at larger angles of heel and
elevation, it just falls short of ISO8729 [1] having a peak RCS of 8.5m2
but
otherwise performs well. It is the heaviest reflector supplied for test at 5.5kg
and costs around £300.
∑ The Echomax 230 narrowly failed to meet ISO8729 during this testing, but
showed good peak and average RCS performance. The reflector is reasonably
priced at £130 and weighs 2.4kg; the main drawback was a RCS drop-off above
an elevation angle of 10˚.
∑ The Firdell Blipper 210-7 narrowly failed to meet ISO8729 during this testing,
but showed good peak and average RCS performance. The Blipper is priced at
£130 and weighs 1.8kg; the main drawback was a RCS drop-off above an
elevation angle of 10˚.
∑ The Standard Tri Lens does not meet ISO8729 as the peak RCS was too low at
4m2
. However its consistent RCS response outperformed most of the other
reflectors when heeled over beyond 10˚; it is reasonably priced at £130 and
weighs 2.5kg.
∑ The Plastimo 16Ē octahedral is inexpensive at £16 and lightweight at 0.65kg
but failed to meet ISO8729 in either tested position. It had reasonable peak and
average performance averaging around 2m2
but had wide nulls which kept its
stated performance level down. Other drawbacks are that its mounting
arrangement is by suspension only (often in an unfavourable position) and
could be subject to damage.
∑ The Davis Echomaster failed to get close to ISO8729 during this testing. Its peak
RCS is too low at 7.5m2
and its average performance is only 1.75m2
. This
reflector is priced at £60 and is lightweight; it can be mounted on a rod as well
as by suspension (in the correct catch-rain position).
∑ The 4Ē tube reflector performed very poorly.
∑ It is concluded that either the active Sea-Me, POLARef and the Standard or
Large Tri-Lens radar reflectors are the best reflectors at heel and elevation
angles of over 10˚.
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