It's not advanced at all. If both antennas are equally efficient, the
ratio of their apertures (in square wavelengths) is exactly equal to the
gain of one relative to the other.

Roy Lewallen, W7EL

Michael R. Davis wrote:
I'm reading an article about antenna aperature. Is it correct to state
that dipoles have a very large aperature and something like a horn
assembly used in microwaves has a tiny aperature except for wavelength
for which the horn is designed?

Just trying to get a handle on this advanced theory.