On Tue, 01 Dec 2009 18:37:51 -0600, tom wrote:

Nice explanation Richard. And I had never put together the
squared-squared relationship. That's a powerful thing to know.

I suppose this is why it ends up that a 1/10 lambda opening is
considered the rule of thumb cutoff frequency on a dish.

tom
K0TAR

Hi Tom,

Radiation resistance certainly plummets quickly. Look at all the
tunable loops for HF that are 1 M in size AND made on an herculean
scale. I don't think any are rated at 80M (Rr ~ 5 milliOhms), and
even less so for 160M (Rr ~ 29 microOhms). This is the principle
reason why Art's inventions are doomed to abysmal transmit performance
in that band (the shoe-box sized 160M loop).

73's
Richard Clark, KB7QHC