Topband: elevated 4-square

[Jeff Blaine]

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
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