"Richard Harrison" wrote in message
...
Jimmie D wrote:
"My first encounter with Gaussian antenna was with microwave relay paths
and "flyswatter" antennas."

We called them periscope systems. Nice because instead of a waveguide
loss, the periscope gave a gain over the dish alone. The reflector at
the tower top has a cupping adjustment to refocus the energy thus
boosting the gain.

When satellite systems appeared, the FCC started to lean on private
microwave users to replace existing periscopes with "high-performance"
dishes at tower tops. Long after we complied, I noticed FAA relay
systems still using periscopes.

Part of the problem with periscopes, I believe, is the common practice
to use tower top reflectoers that are too small, for economy and
performance.

You believe correctly, especially the ones the FAA used.


Part of the would-be illumination is allowed to fall
outside the surface of the reflector. This boosts gain of the periscope
as the outside ring of the illumination is out-of-phase with that in the
center. I don`t know about Gaussian dishes, but maybe they concentrate
in-phase energy in a narrow beam and eliminate the out-of-phase energy.

Best regards, Richard Harrison, KB5WZI