[Antennas] gain vertical

[James Duffer]

Great that your home constructed antenna is working great.

I am assuming that the gain is referenced to an isotropic radiator which is 
truly an omni directional antenna, not just in azimuth but in elevation, a 
spheroid comes to mind as far as a visual representation of the istropic 
pattern.  You hit on the answer your antenna has a dough-nut pattern and 
since it is collinear further gain is obtained in the elevation pattern, 
your dough-nut has been flattened, giving you increased radiation in the 
lower elevation angles and less at the higher.

73, Jim de wd4air

>From: fkamp at comcast.net
>To: "antennas at mailman.qth.net" <antennas at mailman.qth.net>
>Subject: [Antennas] gain vertical
>Date: Fri, 22 Apr 2005 12:30:31 -0500
>
>I just built and installed a vertical collinear for 2 meters.  Two half
>waves.
>
>It is touted to be an omnidirectional gain antenna.  This thing works
>well.  Much better than the 1/4 wave ground plane I was using at the
>same elevation.
>
>Then I got to wondering.  I understand how a beam works.  You get gain
>in one direction because the signal is 'directed' toward the favored
>direction.
>
>I am not sure where the gain comes from in a vertical gain antenna.  It
>is still omnidirectional.  Seems the only thing it plays with is
>take-off angle.  I dont see how that translates to gain.
>
>Regards,
>Frank Kamp
>K5DKZ