On 3/31/2011 7:26 PM, Cecil Moore wrote:
On Mar 31, 7:10 pm, "Richard wrote:
We don't disagree as far as current distribution is concerned, but maybe in
the belief that such a helix at an operating frequency that is 3X its first
resonance has a practical benefit for users.

I'm not saying that it has a benefit - just that a 270 degree
electrically long antenna can never have the same radiation pattern as
a 51 degree physical whip even if the physical length of the 270
degree helical antenna is physically 51 degrees.

To be clear on what I am saying: Up to a certain percentage of a
wavelength, the physical length of the antenna dictates the radiation
pattern. Above that percentage of a wavelength, the theory falls
apart.

It is akin to assuming that the current distribution in the top
portion of a monopole is a straight line. At some point, the straight
line assumption fails because the current distribution is actually
sinusoidal.
--
73, Cecil, w5dxp.com

Cecil -

Do you have an EZnec file you can post? I'd like to see what you're doing.

Thanks es 73,
John