Path: utzoo!attcan!uunet!pyrdc!pyrnj!rutgers!iuvax!silver!commgrp
From: commgrp@silver.bacs.indiana.edu
Newsgroups: sci.electronics
Subject: Re: Circular polarization vs omnidirect
Message-ID: <7200015@silver>
Date: 7 Oct 88 14:34:00 GMT
References: <17770@glacier.STANFORD.EDU>
Organization: Indiana University CSCI, Bloomington
Lines: 25
Nf-ID: #R:glacier.STANFORD.EDU:-1777000:silver:7200015:000:814
Nf-From: silver.bacs.indiana.edu!commgrp    Oct  7 09:34:00 1988




>I have an antenna on VHF that might have the properties you're 
>looking for.  It is from FAA surplus and is labeled circularly 
>polarized, so I guess it is.  It's rather hard to describe, but 
>here goes.  The elements are swastika shaped....
> 
>I assume the FAA wants this kind of antenna to receive equally well
>from airplanes in all directions; and circularly polarized so it
>doesn't care about the orientation of the (linearly polarized) antenna
>in the plane.
> 
>haynes@ucscc.ucsc.edu

Circular polarization helps eliminate "mobile flutter" and other 
polarization-related effects. Another reason for the unusual 
shape of FAA antennas is to achieve omnidirectionality without a 
null zone directly overhead, like that produced by a simple 
vertical.

--

Frank     W9MKV
reid@gold.bacs.indiana.edu