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Re: [TowerTalk] New N6LF Ground Probe Designs

To: towertalk@contesting.com
Subject: Re: [TowerTalk] New N6LF Ground Probe Designs
From: Leeson <leeson@earthlink.net>
Reply-to: leeson@earthlink.net
Date: Tue, 5 Mar 2024 11:47:45 -0800
List-post: <mailto:towertalk@contesting.com>
A couple more re ground and antennas:

J. Breakall, "Maximizing Performance of HF Antennas with Irregular Terrain," 2021, https://www.contestuniversity.com/wp-content/uploads/2021/01/Contest-University-HF-Propagation-in-Irregular-Terrain.pdf

D. B. Leeson, "Antenna Topics," 2007, https://www.kkn.net/dayton2007/w6nl_ant.pdf

On 3/4/24 12:15 PM, Leeson wrote:
I still think of the foreground slope concept as "Moxon Slopes," from the work and publications of Les Moxon, G6XN, who was a great personal inspiration to me.

An interesting related question for which I don't find many references is the HF propagation over a foreground knife-edge ridge that, while lower than the antenna that "sees" over it, is close and high enough to block ground reflection angles up to, say, 12-15°. This includes the complication of diffraction as well as ray tracing. A start is "HF Terrain Assessment" by KR7C, see especially pp. 15-18,
https://k0rv.files.wordpress.com/2015/01/hf-terrain-analysis.pdf

I think the pattern above the ridge, after giving effect to diffraction, is pretty much the same as without the blockage, with "diffraction wiggles" at the point it hits the ridge. But from that elevation angle down to the horizon it seems the lack of ground reflection denies the 6 dB potential gain, but removes the cancellation at the horizon, yielding a regime more like the free-space pattern of the antenna.

For an antenna high enough to see over a ridge, it will typically be high enough to have a substantial number of nulls, once it finally can clear the blockage angle. Any additional comments, techniques and references would be appreciated.

Here are some additional online references that may be of interest in the general subject of ground reflection and slope.

M. Weissberger, et al., "Radio Wave Propagation: A Handbook of Practical Techniques for Computing Basic Transmission Loss and Field Strength," 1962, https://apps.dtic.mil/sti/tr/pdf/ADA122090.pdf

P. D. Rockwell, "Station Design for DX, Part I -- Antenna Topics and Siting," QST, Sept 1966, pp. 50-54, https://www.rfcafe.com/references/qst/station-design-dx-september-1966-qst.htm

G. Hagn, "HF Receiving Antenna Directivity Patterns and Gain for Ionospheric Propagation Model Predictions for Short-Wave Broadcasting," IEEE Trans Broadcasting, Volume 34, Issue 2, June 1988, pp. 221-229, https://ieeexplore.ieee.org/document/1439

J. K Breakall, et al., "The modeling and measurement of HF antenna skywave radiation patterns in irregular terrain," IEEE Transactions on Antennas, Volume 42, Issue 7, July 1994, pp. 936-945, https://ieeexplore.ieee.org/document/299595

R. D. Straw, "What I've Learned in Two Decades of Terrain Assessment by N6BV," video, 2013, https://www.youtube.com/watch?v=D6nRpeVseSc

R. D. Straw, "Terrain Assessment for HF Contesting," 2014, https://seapac.org/seminars/2014/sea-pac2014-n6bv-Terrain%20Assessment.pdf

D. B. Leeson, "Match HF Antennas to the Ionosphere & Terrain," 2017, https://www.dropbox.com/s/hhc00iy6t4h509c/Ionospheric%20Radio%20REDXA_sm.pdf?dl=0

D. B. Leeson, "Siting and Installation of Yagi Antennas," Ch. 10 in "Physical Design of Yagi Antennas," 1992, available online at https://www.dropbox.com/s/hmhkeofz0igrg1e/Physical%20Design%20Of%20Yagi%20Antennas%20D%20B%20Leeson%20V2.pdf?dl=0

73 de Dave, W6NL/HC8L


On 3/3/24 4:43 PM, Brian Beezley wrote:
Just a note that Rudy Severns, N6LF, has put all 35 of his published Antenna Compendium, Communications Quarterly, NCJ, QEX, and QST articles in one place. Each article is a PDF file in magazine format. So much good stuff. Just click on the article you want:

https://www.antennasbyn6lf.com/

The reference I gave to his original soil parameter article was actually to a preliminary version. Here's the final article:

https://rudys.typepad.com/files/qex-nov-dec-2006-soil-parameters-at-hf.pdf

The article N6RK mentioned about determining ground parameters with a low dipole is here:

https://rudys.typepad.com/files/qex-nov-dec-2016-soil-characteristics-using-low-dipole.pdf

Brian

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