Topband: Radials on ground v FCP

[Lee STRAHAN]

According to Roy Lewallens Eznec site there are no more expensive versions of his Eznec software. He is retiring and is leaving a last version for free download.
Take a look at Eznec.com for details.
Lee  K7TJR  OR

-----Original Message-----
From: Topband <topband-bounces+k7tjr=msn.com at contesting.com> On Behalf Of Jim Brown
Sent: Monday, January 10, 2022 1:13 PM
To: topband at contesting.com
Subject: Re: Topband: Radials on ground v FCP

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.

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