[Elecraft] Portable antenna

[Bill Coleman]

On 9/30/02 10:18 AM, Charles Greene at W1CG@QSL.net wrote:

>Three points.  1. The vertical performs a little better than both the 
>Hustler 6BTV with 22 radials and the G5RV on both receive and transmit 
>which it would not do if it were that much worse (5 and 8 dB respectively) 
>that those two on receiving noise.

I have no answer to this other than to ask exactly how you determined 
that the antennas "perform" the same?

>  2. There are many studies that indicate 
>that using more than two (or four for symmetry) radials does not improve 
>the performance of elevated radial verticals.

This is true when the radials are elevated 1/2 wavelength above the 
ground. Near the ground, things get more complex. Of course, we're 
talking about 1/4 wave radials (or longer), not two foot pieces of wire 
as were suggested in the original posting.

There were some computer models that suggested that a small number of 
radials elevated 1/32 wave or so above the ground had the same effect a 
few years ago. Although such installations "worked", when attempts were 
made to compare actual field strength measurements of the ground and 
elevated systems, the ground systems showed stronger field strengths.

I can also point to the study that LB Cebik published recently in the NCJ 
trying various models of ground radial systems in various modelling 
software. The most intriging thing about this report is how widely the 
results varied.

Bottom line: I wouldn't trust the computer modelling of radial systems 
within 1/2 wave of the ground as producing 100% accurate results. 
Corroboration with actual measurements is needed.

>  3. When I modelled the 
>antenna using EZNEC, going from two to 16 radials did not improve the 
>performance at all. In fact, the model showed that 4 radials was less 
>efficient than two.  If you like, I will send you my EZNEC file.

It does not surprise me at all that two 2 foot radials is 
indistinguishable from 16. Make your radials at least 1/4 wave long, and 
you'll see substantially different results.

And again, the model is just that -- a model. It isn't reality.

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901