Re: [TowerTalk] Dayton 2004 Antenna Forum Papers now on the Web!

[Jim Lux <jimlux@earthlink.net>]

At 02:02 PM 5/21/2004 -0500, you wrote:
> If you missed the Antenna forum at Dayton this year, or you were there
> and would like a copy of the presentations, you can go to
> http://www.k3lr.com and click on the 2004 Dayton Antenna Forum button
> and that will take you to K5TR's site where the papers (except for
> W8DMR's) are available.
>
> I hope you enjoy this fantastic information!
>
> 73,
> Tim K3LR
>
> http://www.k3lr.com

I highly recommend:


> "An Investigation Into Ground Systems for Best HF Performance"
> Rudy Severns, N6LF

Some very interesting food for thought there, particularly the plots 
(figure 15, page 13) showing the change in gain for adding radial 
length.  Fractions of a dB (as in <0.1dB) for going from 0.1 to almost 0.5 
wavelength with 16 radials.  Kind of implies that if you have relatively 
few radials (compromise installation), the length is less critical.  Even 
with 64 radials, the difference going from 0.12 to .48 lambda is only about 
a dB.  We can all argue (and probably will) about the effect of a dB 
change, but, in reality, I suspect other factors (like how wet the ground 
is) will have a bigger effect.  Turning on the sprinklers may be more 
effective than installing more and longer radials. (or, maybe you're better 
off slitting the soil to install drip irrigation tubes to keep the earth 
damp than slitting to install copper wires)

I wish he had run some plots for higher frequencies (like 40 or 20m) where 
the lossy capacitive behavior is more important because that figure's for 
1.8 MHz, which is pretty close to the broadcast band, for which the 
resistive approximation works fairly well.

I also like the analysis of grounding systems where the number of radials 
is not constant (fewer radials close in).

Jim W6RMK

P.S. The reference to Sommerfeld's paper should be "Über... Drahtlosen..."  

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