[TowerTalk] Field Strength comparison

[Lux, Jim]

On 9/4/21 8:05 PM, Wes wrote:
> For an illustration try this: 
> http://www.cuminglehman.com/wp-content/uploads/Introduction_to_Antenna_Test_Ranges_Measurements_Instrumentation.pdf
>
> and look at the figure on  page 4.  This shows the usual antenna range 
> situation where the test antenna is receiving a signal from a point, 
> or small aperture source.  This is how I would run this comparison.  I 
> think, but do not know for sure, that I would use the larger dimension 
> of the vertical(s) as the "D" in the equation.  The idea is to have a 
> plane, or near plane, wave over the whole aperture of the test antenna 
> in both directions.  Note that some antennas, Yagis for instance, can 
> have an effective aperture larger that the physical aperture.
>
> Wes  N7WS 


But that's the 2D^2/lambda  - and that comes out strangely small.   And 
it's not effective aperture (that's more about voltage/power at the 
feed) - this is about the physical optics.

D =30m (across the 4 square diagonally) is almost certainly bigger than 
the height of the 80m elements (20m?)