> John Magliacane wrote: > > > It's a traveling wave antenna where the helix is wound around a > > supporting vertical mast that serves as a reflector.
David Woolley <[EMAIL PROTECTED]> wrote: > None of the references I found (including university course > notes), when researching this at the weekend, described anything > other than a dielectric core. They did suggest a spectrum of > behaviour from basically linear polarized, to circular polarized, > depending on the pitch. Johnson's "Antenna Engineering Handbook" (McGraw-Hill) among others describes the antenna design to which I am referring. A preview of chapter 28 where the antenna is described is available at: http://books.google.com/books?id=xTSNJhVlHGgC&pg=PP1&sig=qdNrli_UaJsiZB_gq3cRqvjy4DY#PPT961,M1 Dielectric Communications (formerly RCA) manufactures such an antenna (model TCL) for the purpose I originally described. Their older print catalog describes the antenna in more detail than what is available on the web: http://www.dielectric.com/broadcast/images/tcl1.jpg http://www.dielectric.com/broadcast/vhf.asp Jampro does a better job of describing and illustrating the antenna on-line. In particular, they state: "The JTC Circularly Polarized Spiral Antenna consists of a supporting pole around which are multiple stainless steel spirals wound at specific pitch angles and spaced from the pipe by heavy-duty fiberglass-reinforced low-loss insulators. The array acts as a traveling wave antenna, with the main beam broadside to the support pole and exceptionally low radiation along the axis of the pole. It produces an omni-directional azimuth pattern with low VSWR." Full description and photos are available here: http://www.jampro.com/index.php?page=jtc-circularly-polarized-spiral-tv-antenna 73, de John, KD2BD Visit John on the Web at: http://kd2bd.ham.org/ . . . . ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
