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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