I've never used one of these, but the idea is interesting:

http://www.speedseal.com/seame/welcome.htm

.... it apparently works along the same lines as a SART, enhancing your
radar "blip" by using an active transponder.

Two other points I'd add:

We used the "el cheapo" Davis reflectors on drift buoys on the research
ships I've been on. With the reflector, the buoys were usually visible
on radar at 10-12 nm out, without the reflector they were almost
entirely invisible to the radar no matter how close we were. Not very
scientific, but pretty good evidence that they work IMHO.

No matter how "good" your radar reflector, it by no means replaces your
need to stand an alert and vigilent watch.

--

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On Mon, 21 Feb 2005 08:06:54 -1000, renewontime dot com
wrote:

We used the "el cheapo" Davis reflectors on drift buoys on the research
ships I've been on.

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Offshore commercial fishing boats also use them to mark their buoys
which is a pretty good recommendation. I have carried a small folding
Davis for years which I assemble and display in foggy conditions,
usually elevated on the end of a boat hook. I've been told that it
shows up well. On the other hand my new 4KW Furuno radar has no
problem picking up small boats of all types at 2 to 4 miles, at least
in flat water conditions.