Steve Jernigan wrote First, any conductive material placed in the near-field an antenna will de-tune it. When placed near (or in contact with) the tip, it will lower the resonant frequency of the antenna by an amount dependant on how much and how close. There is not really all that much metal in a metalized mylar film, so the effect will probably be fairly insignificant. For the same reason, I'd expect the mylar film to be a not particularly effective reflector of microwave (radar) radiation. The best suggestion I can offer is to try a with / without experiment, coordinating the efforts with your yachting friends on VHF. That might give some indication of how much effect the pennant is having on your antenna as well. Peter Rattenbury wrote: - It was a perfect ellipse, in other words a regular oval or egg-shaped device, divided into four quarters. The kite string was attached at the longtitudinal ends of the ellipse, and the whole thing spun on its axis. Matt Broze wrote: - Someone should test a metalized helium balloon as kites are hard to keep in the air from a kayak even on a windy day. Of course the balloon would be blown down to sea level in much wind. Advertised in our local yachting shop were a number of radar reflectors including a very expensive one which is apparently used by NATO as a low volume, high apparent area reflector responding over 360 degrees and down to 30 angles of heel. It answered to Peter Rattenburys description of the inventor's rotating egg shaped device. I'ld hazard a guess that it contains a metallized flat sheet which is also rotating, but I'm not about to buy one and and pull it apart! A quick check through some ancient text books, suggests that at 9GHz a metallized sphere shouldn't work as well as a corner reflector or a metallized pennant fluttering through 90degrees in the wind (not to mention pinwheels!). The metal on aluminised foils is probably about 0.1 micron thick and I make the skin depth for 9GHz about 0.7 micron, so as Steve suggests, these foils may not be optimal (I'm no radar expert though). A lot of these films are not continuous metal so would they really change the antennae characteristic? Would it help to extend the insulator and keep the reflector away from the antennae? The yachtie mates liked the antennae and pennant idea for optical visibility but few of them carry radar and generally only use it outside the harbour. However, I think the local volunteer coast guard might and a few weeks ago they were showing a healthy interest in foldable kayaks so may be able to trade free rides on the Klepper in exchange for radar tests. Sadly it will have to wait til after rough water self rescue practice and tether trials, which are coming up on the horizon very rapidly. All the best, PeterO *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Fri Aug 20 1999 - 03:50:18 PDT
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