[TowerTalk] Choke on feed point of dipole

Wed Jan 14 11:20:53 EST 2026

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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