I forwarded some radar questions to a friend who works on all sorts of FAA and DoD radar systems, and here are his (heavily edited) comments: ;-) > I can't believe that people pfutzing around with paddles and little bath-tub > toy boats even know how to spell radar, forwards or backwards.... Yeah, I'll get him for that... > ...Which brings up a nasty fact that if this thing is floating around at water's > > level, it ain't gonna be seen too well by a ship-board radar --- there's a > nice null in the radar's antenna pattern at the waters' surface. You want to > raise it up a bit; at least a few wavelengths (at 3 cm, the "X" band marine > radar wavelength) -- like a foot or more. So you'll need to mount it on a > stick poking up through your kayak; or on top of your kayaker's Official > Nutcake Helmet, or maybe on a mast on a styrofoam boat roped behind your > kayak, a kind of a towed decoy to attract semiactive homing missiles away from > your stealthy kayak to your corner reflector ball. Better use a long rope. [snip] I asked him about embedding a reflector in foam: > Styrofoam is pretty radar invisible at these frequencies, until you get it > wet. So imbedding the retroreflector into a ball of styrofoam is probably a > bad idea; they one's I've seen just hang out there buck naked, crude foil and > all, merrily blowing in the wind. So if we do that we'll have to use closed-cell foam, which we would anyways, or just seal it up watertight. Retroreflectors are those devices made of three plane surfaces at right angles. (Water attenuates RF at those frequencies; that's how your microwave oven works.) Now, if you *really* wanna stand out... > The other thing you could do is buy one of those cheapo x-band "radar detector > testers", tweak it to the marine radar frequency, modulate it with pulsewidths > and repetition frequencies as used by marine systems, and radiate the signal > through an omni antenna. Then every time a marine radar swings by they'll get > a whole mess of nice strong blips on their screen -- they won't know where you > are in range, but they will likely avoid any heading near your direction! > Unless they happen to have a HARM on board..... HARM = high speed anti-radiation missile ;-) This does suggest that an X-band radar detector would be handy in the fog to see if you were being interrogated by radar.... -- Michael Edelman http://www.mich.com/~mje Telescope guide: http://www.mich.com/~mje/scope.html Folding Kayaks: http://www.mich.com/~mje/kayak.html Airguns: http://www.mich.com/~mje/airguns.html *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Does anybody know about beer cans? Some people here believe that they are very visible to radar... and somehow, there are often empty beer cans available ;-) Cheers, Ari Saarto "In the not-so-cold-as-you-might-believe Fin-land" Kannaksenkatu 22 / P.O. 92 15141 Lahti - Finland - Europe GSM +358 - 50 - 526 5892 fax. +358 - 3 - 828 2815 e-mail: asaarto_at_lpt.fi *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Bruce Winterbon wrote: > >> Styrofoam is pretty radar invisible at these frequencies, until you get it > >> wet. So imbedding the retroreflector into a ball of styrofoam is probably a > >> bad idea; they one's I've seen just hang out there buck naked, crude foil and > >> all, merrily blowing in the wind. > > > I read "radar invisible" as being transparent to radar, so embedding > something in styrofoam is not significantly different, to the radar beam, > from embedding it in air. > Correct. The critical issue was that if the foam absorbed water, the water would attenuate the signal. -- Michael Edelman http://www.mich.com/~mje Telescope guide: http://www.mich.com/~mje/scope.html Folding Kayaks: http://www.mich.com/~mje/kayak.html Airguns: http://www.mich.com/~mje/airguns.html *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
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