On Mar 22, 8:56*pm, tom wrote:

Do you have any web references to gridded cavity antennas?

A good source is the paper from which I posted a few "fair use" clips,
and was published in the Sept 1979 edition of the IEEE Transactions on
Broadcasting. I'm not aware of any web link to it, and it is a
copyrighted work. But probably your local public library would be
able to access it through inter-library services, and provide you with
a copy.

This design was developed by Harris Corporation, and has evolved/
improved over the years especially in the crossed-dipole element used
to excite the cavity.

The design is now available through several manufacturers. The first
link below shows a description of it from the 2004 catalog of
Dielectric Communications, who bought the design from Harris. The
picture shows an array of 12 layers of 3-around cavities that was
built by Harris as a master FM antenna (9 stations) for the Senior
Road Tower Group in Houston.

The second link below shows the measured axial ratio for an
omnidirectional version of the antenna.

http://i62.photobucket.com/albums/h8...vity_Array.gif

http://i62.photobucket.com/albums/h8...xial_Ratio.gif

RF