Infinite F/B ratio? I get the impression that we're talking about a
multi-bay FM antenna that should be omnidirectional in azimuth... Do
you mean infinite horizontal to zenith ratio? Or Front-to-Side ratio
if it were installed horizontally? Maybe I'm missing something. I
guess I'm missing Kraus's book! We're not talking a unidirectional
beam here, right?

A 5x5 planar dipole array with a 2:1:1:0.1:0.1 ratio spaced on a 1/2
wavelength grid gives a nice clean bidirectional beam with "no"
sidelobes.

A pair of these arrays spaced 90 degrees and fed 90 degrees makes a
nice unidirectional clean beam with good F/B and low rear lobes, and no
front sidelobes.

Not envious of someone who tries to build a distribution harness for
this thing, though.

http://www.n3ox.net/projects/eznec/dipole_array_144.ez

73,
Dan