|Subject:||Re: [TowerTalk] Dayton 2004 Antenna Forum Papers now on the Web!|
|From:||Jim Lux <firstname.lastname@example.org>|
|Date:||Fri, 21 May 2004 17:02:35 -0700|
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 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).
P.S. The reference to Sommerfeld's paper should be "Über... Drahtlosen..."
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
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