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post #1 of 10 Old 06-07-2007 Thread Starter
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radar reflectors

Found this from another link supplied in a different thread.
I thought it very interesting.
Lots to read through.
I was surprised by the findings.
I always thought that the tube type reflectors were the choice of most sailors. These findings result in a different recommendation.

Of course the best protection will cost you a lot more $$$$


http://www.setsail.com/c_central/tec...Reflectors.pdf


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post #2 of 10 Old 06-07-2007
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Frightening isn't it. However, I wonder how two or three tubular reflectors might fare, one on each shroud and one on the backstay.
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post #3 of 10 Old 06-07-2007
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Having multiple radar reflectors can actually work against you from what I've read. Having one good one is probably the way to go.

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post #4 of 10 Old 06-07-2007
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I might beg to differ with the dog on that one, although i have no evidence to back it up. I would say, from the test results, it does appear that you would have three poorly performing reflectors.

The problem with small boats is that they easily disappear amidst the seas and rain squalls. Although, even ships will disappear in rain squalls. Unless you are steel or aluminum hulled, you are only going to "paint" a ship's radar screen sporadically. Anything you can do to enhance your radar return is advantageous. Multiple reflectors might do that, although additional inefficient ones may not be worth it. Certainly, if you were on a ketch, and could afix multiple high quality reflectors to each mast, I believe you'd increase the frequency of "painting" ship's radar. Regardless of type of reflector, excluding active units, a great many of your echos are going to be reflected either skyward or down into the sea. The boat and reflector are rarely aligned with the incoming radar beam sufficiently to give a good and consistent return. That is one of the reasons that radar watches must be actively held by a crew member, not relying on the "computer".

For multiple reflectors to work against each other they'd have to mounted in close proximity, thereby inducing some type of cancelling effect. As any motorist, dedicated to high speed travel, can tell you, this is very difficult to achieve.(g) Although, mounting them close to one another might induce false echos, that is to say, inaccurate ranging on board the radar equipped vessel.

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post #5 of 10 Old 06-07-2007
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There is a great (and frightening) article in Panbo on this. Look here: Panbo: The Marine Electronics Weblog: Radar reflectors, do they really work?
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post #6 of 10 Old 06-08-2007
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Quote:
Originally Posted by sailingdog
Having multiple radar reflectors can actually work against you from what I've read. Having one good one is probably the way to go.
Complex subject. The individual returns could cancel, if of nearly equal strength. But the test results for a single reflector show that the observed elevation angle plays a significant role, so having several reflectors at different elevation angles is likely to mean that the strongest return will dominate.
Also in that QineteQ report, did you see the range fades on the 4m target, 30m radar? Those will move about with changed assumptions, but they show the weakness of this type of radar. Even a 10m2 reflector will vanish from the screen at certain ranges. Hence having multiple reflectors at different heights might compensate a little.
On the SeeMe transponder, they didn't test how it responds when the yacht's own radar is on. I suspect that the SeeMe will continuously respond to the yacht's radar and consequently be rejected by the ship's radar, just as it rejects the yacht's radar signal as not being one of its own returns.
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post #7 of 10 Old 06-08-2007
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Ocean Navigator Online
Ocean Navigator Online - Radar reflector performance

An article in Ocean Navigator, March 2006, by Gallman on passive radar reflectors (he also has a book on the subject) rates reflectors. Bottom line: Tri-Lens (large size) is best while the Davis octahedral is OK and much less expensive.

The boat's angle of heel and pitch is the biggest factor in performance and while most people mount the Davis in the recommended "rain catch" position it's suggested the Davis in the "rain catch" down position will reflect best for boats with low heeling tendencies.

So the question is, why not an Davis EchoMaster on each spreader in both orientations?
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post #8 of 10 Old 06-08-2007
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Most sailboat owners choose to install those "tubular" reflectors since they're relatively unobtrusive. I've read articles that report, in spite of the lower costs, the Davis Echomaster actually outperformed them. I have yet to be fully convinced that I should switch - although ronbo raises an interesting possibly.

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post #9 of 10 Old 06-08-2007
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I've had the large Rozendal Tri-Lens reflector on my last two boats, and I am told I paint like a large ship on my friends' radars. I wouldn't feel safe boating in this area without it. Sequitur's is 10 metres up the mast, just above the radar.

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post #10 of 10 Old 06-08-2007
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