[TowerTalk] Ground mounting vs roof mounting verticals

[David Gilbert]

That's not really true.  Elevated radials don't have to be resonant for 
an antenna to work well, or even be resonant.

It is possible, for example, to have the COMBINATION of the vertical 
element and the radials be resonant ... the feedpoint impedance will 
just be higher than the classical 33 ohms.  Think off-center fed 
vertical dipole, except with a portion of the lower part of the "dipole" 
splayed out.  I've built antennas that way and I've modeled them with 
EZNEC as well ... it works.  Several hams have compensated for a 
not-quite-quarter-wave vertical by making the elevated radials longer 
than a quarter wave, and it works the other way as well (longer 
vertical, shorter radials).  Either way, tuning is a bit trickier than 
if the vertical element and the radials were each a quarter wavelength, 
though.

And, of course, if the combination of the vertical element and the 
radials is not resonant, it will still work fine if you use the proper 
matching network to feed it.

As far as feeding a vertical element against a yagi for a ground plane 
.... well, that's pretty much a crap shoot and it would take a lot of 
trimming of the vertical element if you want to make it resonant.

73,
Dave  AB7E




Gary Schafer wrote:
> An elevated vertical must have resonant radials.
>
> 73
> Gary  K4FMX
>
>
>