Peter Duniho wrote:
"Dennis O'Connor" wrote in message
...

Larger is better, however... Look at the dish at Arecibo for example..
http://www.rainforestsafari.com/observe.html


Radio antennae such as that one use reflection, not refraction, to focus
radio waves. In fact, I'm not aware of a single refractor radio antenna.


There are indeed refracting antennas. A common type is a dielectric
antenna in the form of a plastic "wedge" shape that protrudes, for
example, from the end of a waveguide. Various vehicular "speed radar"
detectors used antennas like this in years past. Microwave antennas
can also employ solid lenses, made of materials like polystyrene, and
for larger lenses that would be heavy, a matrix of plastic balls
with an overall lens shape serves the same purpose while saving weight.
A convenient material to experiment with for making you own dielectric
antennas is common paraffin wax.

Tom Pappano, PP-ASEL-IA