omnidirectional circularly polarized FM antenna

[Garrett Wollman]

<<On Sun, 19 Nov 2006 22:31:07 -0500 (EST), Ric Werme <ewerme@comcast.net> said:

> Finally, what does an omnidirectional CP transmitter antenna look like,
> anyway?  The vertical component is no problem, of course, but does the
> horizontal part need some serious compromises?

TV antennas, of course, are mostly horizontally-polarized, although
some are also circular and some are elliptical.

On the FM side, some of them use separate H and V sections, and some
of them use an integrated circular design.  Shively's 6814 
<http://www.shively.com/ds-6814-hw.php> is of the latter design; you
can also compare their 6812B <http://www.shively.com/ds-6812b-hw.php>.
A pure-vertical antenna is shown at
<http://www.shively.com/ds-6510-hw.php>, and a pure-horizontal looks
like this: <http://www.shively.com/ds-6600-hw.php>.  The 6017 is a
broadband CP antenna and is perhaps the clearest photo to look at:
<http://www.shively.com/ds-6017.php>; compare the broadband panel
6016P: <http://www.shively.com/ds-6016p.php>.  Similar products are
available from ERI, Dielectric, and several other manufacturers; if
you are so inclined, you can get data sheets from many of them.

-GAWollman