Julio MacWilliams wrote: > ...Putting an internal sheet of aluminum foil should serve as a radar > deflector A simple flat surface doesn't make a good radar reflector, as the trasmitted beam will be not provide a decent return unless the surface is directly facing the radar set. That's the purpose behind the design of the F-117 Stealth, if you've ever seen one; all those flat surfaces reflect the radar beam off away from the radar antenna. > , but according to Derek Hutchinson's book even a commercial > radar deflector on the deck of a kayak is sitting to low to be effective. > He says that a ball of aluminum foil wrapped on the tip of a fishing pole > is way better. If I knew someone who had a boat with radar I could > test that. A sphere will always reflect *some* of the transmitted energy back to the radar, although with diminished intensity. So a ball is better than a plate. The radar reflectors you see commonly are made with three flat surfaces intersecting at right angles. This creates what's called a corner reflector, a geometry that will reflect a transmitted beam directly back at its source over a wide area. Automobile tail light lenses are made with the same geometry for the same reason- lots of tiny cubes that will brilliantly reflect a headlight. Imagine a pair of mirrors set at right angles. Trace the various paths of light entering and exiting and you'll see how this works. (Light reflects off a mirror at the same angle at which it strikes the mirror) Thus it occurs that this all-purpose device we're designing could have a corner reflector embedded in it. You could embed thin plates or metal foil in foam. Four pieces of foam seperated by metal foil or screen, glued together, would make a great float/reflector combo. > ...> Or maybe you can incorporate some mylar film in the design and create > > a radar reflector for SAR purposes, too. That might work, too, if the mylar had a good conductive metal film. I'll e-mail a pal of mine who designs radars for various airborne systems and see if I can't get some better ideas from him. ---------------------------------------- Michael J Edelman mje_at_mich.com http://www.mich.com/~mje http://www.mich.com/~mje/kayak.html http://www.mich.com/~mje/scope.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/ ***************************************************************************Received on Wed Mar 18 1998 - 14:03:34 PST
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