Topband: Radials on ground v FCP

[Jim Brown]

As usual, I agree with Rick.  But I'd like to observe that an extensive 
study of loaded mobile whips published in two parts in QEX about ten 
years ago showed that inductive loading, especially at the base, was a 
bad idea, and that the closer loading moved to the top, the more 
efficient was the radiated field. The published work included extensive 
measurements of various positions of the loading, with top loading being 
the best. Which is what we're doing with both the L and the T.

One fly in the ointment in our understanding is that most modeling 
software, especially if it models inductive loading as a lumped element, 
fails to correctly model the phase of current through the inductor. Some 
years ago, W7EL added a method of modeling inductors using his EZNEC 
interface as a large number of small inductors in a spiral geometry, in 
an attempt to correct for this. Thus a practical inductor could include 
hundreds of (or even a thousand) elements, so it requires one of the 
more expensive versions of his software, and takes a while to crank.

73, Jim K9YC

On 1/10/2022 11:24 AM, Richard (Rick) Karlquist wrote:
> Actually, you are kidding yourself making the inverted L long enough to 
> be resonant.  That has the effect of moving more current into the 
> horizontal part of the inverted L, which is also not desirable.  The 
> solution to this dilemma is to use a top loaded (T type) vertical, and a 
> loading coil if necessary.  The resonant inverted L is "elegant" but not 
> optimal.