[TowerTalk] 10M phased verticals

[Jim Lux]

On 11/29/11 12:25 PM, Rick Karlquist wrote:
> With a vertical up to 1/4 wave long, the base current
> is the same as the current lobe.  Thus you can control
> the phase and magnitude of the current lobe by controlling
> the base current.  When you exceed 1/4 wavelength, then
> the current lobe moves up the vertical above the base.
> And the current lobe has a different value than the base
> current.
>
> The more you exceed 1/4 wl, the harder it is to control
> the current lobe by forcing the base current.  When the
> vertical reaches 1/2 wl, you have to force the base
> voltage to force the current lobe.  However, the relationship
> between the forcing voltage and the current lobe depends on
> stray capacitance around the base, so it is unpredictable
> in practice.  (However, it works great on EZNEC).
>


Ah yes.. excellent point.
  For  elevated vertical dipoles, too, the current forcing would work 
fairly well.

But for end fed schemes (1/2 and 5/8 wave) I can see where getting the 
right excitation would be tough and VERY sensitive to small changes in 
feedpoint Z.