Jeff,
You can also use EZNEC to simulate the effect of the driving point
impedance on the array's behavior. It doesn't take too much additional
effort to learn how to incorporate lumped elements, transmission lines and
transformers into your antenna model.
If you have a copy of the most recent edition of ON4UN's "Low Band DXing,"
there are numerous example models on the CD that you could adapt to your
situation.
73 -- Brian/K1LI
On Fri, Aug 16, 2013 at 1:46 AM, Jeff Blaine <jeff@ac0c.com> wrote:
> What affect is there of vertical *resistance* variations are the common
> 4-square boxes?
>
> N6LF’s QEX article shows quantitatively the performance hit associated
> with using non-resonant elevated radials. Which is interesting because
> non-resonant radial lengths reduce the sensitivity of individual elevated
> radial variations from ideal. However, by altering the relative lengths of
> the vertical/radial, the feedpoint R moves around.
>
> I ran a simple test case pair in EZNEC. First was the resonant radial
> case (length is the same as the vertical radiator). Second was shortened
> radials (about 10%) with the vertical lengthened to restore the same X=0
> frequency. The feedpoint R moves from 32 ohms in the symmetric case to
> about 40 ohms in the short-radials case.
>
> The R has got to translate into a drive impedance shift - but I am
> wondering what the expected impact to the array should be?
>
> 73/jeff/ac0c
> www.ac0c.com
> alpha-charlie-zero-charlie
>
> _________________
> Topband Reflector
_________________
Topband Reflector
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