On Mon, 1 Dec 2008 08:27:22 -0800 (PST), Art Unwin
wrote:

I have had a similar antenna
for the 80 metre band where the helix diameter
is just 4" which is quite directional even tho as low as 30 feet!.

My transistor radio antenna of 50 years ago was smaller than that and
could do better at lower frequencies: Triple the wavelength, 4 times
smaller, and at one tenth the height. That is a 120 fold advantage
over your design. It cost $12, and the antenna came with it for free!

73's
Richard Clark, KB7QHC