"Dave" wrote in message
...

"Art Unwin" wrote in message
...

Well the idea of 1 inch mesh was a bum idea. I should have kept to my
own thinking.
When transmitters have holes in the casing of 1 inch diameter will be
the time I will use such large holes.
Will now have to take it of and replace with aluminum window mesh.
The present mesh has no idication of working in any sence of the word
Art

let me give you a hint... its not the mesh that is the problem.


The theoretical gain of a dish is expressed as (9.87 times D-squared) /
(wavelength-squared), where D is the dish diameter. If you have a 3 meter
dish and you're working 10m, I calculate the gain as less than unity. Ref:
http://en.wikipedia.org/wiki/Parabolic_antenna

Even then, the efficiency of the dish is assumed to be 100% -- which it
never is. One limitation is the effectiveness of illuminating the entire
surface of the dish uniformly. How can you do that at HF? You need a
compact illuminator at the focal point of the dish but HF doesn't lend
itself to such gyrations.

I think you should not consider a dish for HF. It works only for
wavelengths that are small, compared to the dish size. Don't fight the
math.