Sent from my Galaxy
-------- Original message --------From: Leeson <leeson@earthlink.net> Date:
3/4/24 12:15 PM (GMT-08:00) To: towertalk@contesting.com Cc: Brian Beezley
<k6sti@att.net> Subject: Re: [TowerTalk] New N6LF Ground Probe Designs 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.pdfI 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.pdfP. 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.htmG.
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/1439J. 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/299595R. D. Straw, "What I've Learned in
Two Decades of Terrain Assessment by N6BV," video, 2013,
https://www.youtube.com/watch?v=D6nRpeVseScR. D. Straw, "Terrain Assessment for
HF Contesting," 2014,
https://seapac.org/seminars/2014/sea-pac2014-n6bv-Terrain%20Assessment.pdfD. B.
Leeson, "Match HF Antennas to the Ionosphere & Terrain," 2017,
https://www.dropbox.com/s/hhc00iy6t4h509c/Ionospheric%20Radio%20REDXA_sm.pdf?dl=0D.
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=073
de Dave, W6NL/HC8LOn 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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