On Sun, Jun 26, 2005 at 02:08:48PM -0400, Wes Cosand wrote:
> Folks:
>
> I am embarrassed to ask a question I should be able to figure out but my
> Handbook and Antenna Book aren't proving sufficient to overcome my ignorance.
>
> How can I calculate the field strength in volts/meter as a function of
> distance from an isotropic antenna emitting a given power in watts? (Let's
> ignore the near field/far field issue.) Where does a ham go for this kind
> of information?
>
> Thanks
>
> Wes, WZ7I
Wes,
I haven't come across any texts which discuss this, but you can look at
the situation as a sphere with a radius equal to the distance from the
antenna which has a uniform power density. Calculate the surface area
of the sphere (4 PI R^2) in square meters. Divide the power radiated by
this value and you have the power density in watts/square meter. Since
E^2 = RP, you multiply the power density by the impedance of free space
(377 ohms) and take the square root of that result to get the field
strength in volts/meter.
73, Bob N7XY
--
Bob Nielsen, N7XY n7xy (at) n7xy.net
Bainbridge Island, WA http://www.n7xy.net
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