Sonny Hood wrote:
On Wed, 27 Feb 2008 15:05:54 -0800, Roy Lewallen
wrote:

The gain and pattern will be very close to that of a dipole at a height
of about 24 feet. Maximum field strength will be straight up, and quite
dependent on the ground characteristics.

What's a point incident antenna?

Hi Roy, I consider it the radiation point of a "0" length element
which radiates in spherical direction.

Oh, that would be an isotropic source. Gain relative to an isotropic
source usually assumes that the source is in free space, so you get an
automatic 3 dB of gain when you restrict your antenna to a hemisphere by
adding a ground plane.

There's no single answer to your question, since the gain is strikingly
different in each direction and at each elevation angle. The maximum
gain occurs straight up, and you'd only be interested in that figure if
you're doing NVIS work -- and it would vary quite markedly depending on
ground conditions.

The simplest way to find the gain relative to isotropic (dBi) at any
particular azimuth or elevation angle is by modeling. The free EZNEC
demo program at http://eznec.com is adequate, and the Test Drive
tutorial in the included manual takes you through the building of a
similar antenna. You can easily modify the example to imitate your antenna.

Roy Lewallen, W7EL