> From: "PeterO" <rebyl_kayak_at_iprimus.com.au> > Its always puzzled me why hand held shortwave transceivers aren't sold. They > would surely represent the most reliable hand held communication in remote > areas. There are such transceivers- Mizuho of Japan made a wide range of them. The problem, though, is antennas. VHF radios can get by with stubby inductively-loaded antennas with a physical size of perhaps a tenth of a wavelength, but lower frequencies require proportionately bigger antennas A transceiver operating around 4MHz would require an antenna of quarter-wave size (roughly 18 meters in length for reasonable efficience. You can use inductive loading to make a reasonably effective antenna of perhaps 2-3 meters in length, but efficiency goes way down. Remember those giant WWII walkie-talkies you'd see John Wayne carrying in the movies? They operated around 3-4 MHz, used a ton of batteries, and had a useful range of about a mile. -- mike -------------------------- Michael Edelman http://foldingkayaks.org http://findascope.com *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Thu Jun 10 2004 - 07:25:53 PDT
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