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).
Rick N6RK
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