Tom Rauch wrote:
> > If both antennas have the same gain they will have the same
> > directional properties.
>
> No, that is not true.
>
> The antennas can and often do have vastly different directional
> properties even with the same gain.
> 73, Tom W8JI
> W8JI@contesting.com
I guess I should have qualified that a little better. I did say that one
may have a sharper vertical pattern and the other a sharper horizontal
pattern. What I meant by that over simplification was that for a given
amount of gain in one direction, gain has to be reduced in another
direction.
By the "same directional properties" I meant that they will have the
same total beam width exposure to the sky. (not necessarily in the same
direction) This total beam width is the sum of both vertical and
horizontal beams.
One antenna may be a vertical collinear type with 360 degree horizontal
pattern but it's vertical pattern will be very narrow. Another antenna
may be a bi directional vertically stacked dipole array. It will have 2
major horizontal lobes and a very narrow vertical pattern. A yagi of
course has a 1 major horizontal lobe in one direction and a suppressed
vertical pattern.
If you add up all of the area of the sky that each antenna beam is
exposed to due to each ones horizontal and vertical beam widths, I think
you will find that given the same gain for each they will also have
equal total exposure area.
In other words you can not have gain without without having a
directional antenna.
73
Gary K4FMX
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