[TowerTalk] New N6LF Ground Probe Designs

[David Gilbert]

I have played around with HFTA using terrain files that I manually 
generated by simply editing an existing file to create cliffs and sharp 
ridges.  It's very easy to do and comes up with interesting results, 
although I can't speak to their validity.

One interesting experiment is to create a terrain object that is not 
symmetrical ... for example gentle upward slope on one side and sharp 
decline on the other side.  The results for low angles are of course 
different depending upon the incident side, which I have always felt 
could contribute to the fairly uncommon "one way skip" that I and others 
seem to have experienced.

A significant limitation of HFTA, though, is that it won't show RF at 
any angle below zero elevation even if you have a 2,000 foot tower.

Dave   AB7E




On 3/4/2024 1:15 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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