Hi Jim,
I appreciate your ongoing comments/insights into antenna systems. I am
considered an "antenna expert" by my local club, however I usually find
your comments instructive. (Note that an "expert," like a "professor"
is normally just a couple of pages ahead of the audience in the
textbook...) Please ignore Dave's comments and personal attack on you.
73 -- Larry -- W1DYJ
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Larry Banks | Amateur Extra
Licensed in 1961 | W1DYJ since 1966
http://www.qsl.net/w1dyj/
ARRL Life Member
ARRL Diamond Club
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On 1/14/2026 09:57, David Gilbert wrote:
FFS Jim, I know all about the effect of ground specs on vertical
antenna performance and the difference with horizontal polarization.
I used the default specs BECAUSE I WAS ONLY MAKING A COMPARISON! I
don't need a lecture from you on the basics. I don't need a history
lesson from you on your past experiences and I don't need to go to
your website to learn basic stuff I already know.
What is with you??
I didn't try to show a pattern plot overlay here because this
reflector won't accept images, but I gave the angle and magnitude
comparison of the maximum signal strength TWICE for you.
Lastly, you're preaching to the choir about the difference a dB or 2
can make on the chances of making a QSO. I'm the guy who did the
study on that effect with the Minimal Discernible Difference audio
comparisons that I had on the Weak Signal Files page of my AB7E.com
website. That website is currently offline, but you can still find
the material on the Internet Archive at:
https://web.archive.org/web/20211201014151/http://www.ab7e.com/weak_signal/mdd.html
So just stop, OK?
Dave AB7E
On 1/14/2026 4:35 AM, Jim Brown wrote:
On 1/13/2026 1:53 PM, David Gilbert wrote:
Default ground specs were used. (0.005/13 over Real/MININEC)
Ground quality both close to our antenna and in the far field have a
profound effect on vertically polarized antennas. There's useful
information in my study of the heights of vertical antennas, and how
they, and the signals they radiate, interact with the surface of the
earth, for soils that differ greatly from one QTH to another.
Verticals care as LOT about ground quality and a bit about height.
The electromagnetic nature of the soil varies a LOT from one QTH to
another. In granite mountains where I live, ground is lousy for RF.
30 miles to the east is Silicon Valley, wildly developed, so lousy
ground. 50-7 miles to the east is fertile soil with pretty good
electromagnetic properties, another 30 miles east and it's wine
country, not great soil for radio. That's where N6RO is, and they
were never the biggest signal on the lower bands when I lived in
Chicago, even though they had a great antenna farm.
Horizontal antennas care NOTHING about soil quality but EVERYTHING
about height.
I live in the Santa Cruz mountains, which is mostly granite with a
layer of "duff" -- a rather absorptive soil comoposed of centuries of
the small bits of vegetation that fall off the redwoods throughont
the year, but especially during storms. As we walk through it, our
feed are cushioned by the softness of it. Well into our rainy season,
when that duff gets increasingly saturated, the only useful vertical
in my antenna farm, a Tee for 160M, works better. On higher bands,
the absorption from the trees and the lousy soil makes verticals
useless, while high dipoles for 80 and 40 work great. The highest
dipole I could rig for 160M was at 120 ft, not quite a quarterwave.
The optimum height of a horzontal antenna for those lower bands is
1/2 wave.
A horizontally polarized antenna at a quarter wave is as low
antenna, with poor field strengthen at low to mid-high angles. For
more than two years after I moved here, I had a 160M dipole at 120 ft
and a 100 ft Tee with a lot of on-ground radials, some pretty long,
some shortened by the location of buildings and other concrete. I did
a LOT of on-the-air comparisons with the two, and the dipole rarely
won (but it did with certain propagation conditions, as any on-air
student of propagation who could have switched between multiple
antennas would have experienced.
I strongly suggest that you look at my work on this, and that you
follow my suggestions in an earlier post about plotting the vertical
patterns of the two antennas on the same axes. There, and using the
cursor to put dB numbers to the differences, we see that the antenna
whose current maxima has significantly greater field strength at
lower angles, which, on average, makes for greater DX performance.
Yes, a few dB. But any serious contester in a limited station will
tell you that 2 dB, and sometimes 1 dB, can be the difference between
a QSO or not; or longer to make it with QSB.
Being sure of ourselves is not a great way to learn stuff we missed
the first time around.
73, Jim K9YC
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