Re: NEC-LIST: QUESTION

The difference is real. A great deal of the power radiated from a
vertically polarized antenna is lost in the reflection from ground. This
reflection takes place mostly beyond a typical ground radial screen.

To get a quantitative idea of just how much power is lost by this
phenomenon, specify average gain calculation on the RP "card" and note
the difference between horizontal and vertical dipoles. To get a better
idea of the mechanism, note the different equations for reflection
coefficient for vertically and horizontally polarized waves in any
edition of Kraus' _Antennas_.

Roy Lewallen

Don Belcher wrote:
> Hello,
> I am a fairly new user so this is probably a dumb question but I have been
> comparing simple half-wave dipoles over typical earth, oriented vertically and
> horizontally. The patterns look as you would expect however if one overlays
> the patterns, it sure looks like the horizontal is radiating a lot more
> integrated power than the vertical (meaning it looks like the overall
> radiation efficiency of the antenna/earth "system" is higher with the
> horizontal). Of course the overlays are at the broadside azimuth for the
> horizontal....
>
> Just for grins, I am using a 21 MHz half-wave dipole about 20 feet high at the
> feed point.
>
> Is there some factor of 2 or something similar that I am missing or is it all
> pattern effects and fooling me bacause I am looking at the horizontal's best
> azimuth?
>
> thanks
> Don
> dbelcher_at_wherenet.com

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