[TowerTalk] Choke on feed point of dipole

[David Gilbert]

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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