Please take this with the grain of salt that it deserves. I am not the
author and am only quoting what I read (or thought I read). The 1978
article on shortened antennas and radials is available from the QST
archive and makes for interesting reading.
John -- WA1JG
On 1/5/2011 4:44 PM, Richards wrote:
> Er... ah... No joke. Do you doubt the proposition that a
> good ground plane lowers radiation take off angle? If so,
> I would be curious as to your reasons. (Seriously, and with
> no intention to flame or cause an argument, as I have
> made quite an investment in time and resources in vertical
> developing a reasonably decent vertical antenna system
> for my small, suburban back yard. Any info would be
> greatly appreciated. )
> FYI ---
> ------ Extra Class Exam Questions of interest -----
> Question E9A12 - and the answer is that the efficiency
> of a quarter wave grounded vertical antenna can be improved by
> installing a good radial system.
> Question E9A13 - answer is - soil conductivity is the most important
> factor in determining ground losses for a ground-mounted vertical
> antenna operating in the 3-30 MHz range.
> Question E9C13 - answer is - When a vertically polarized antenna
> is mounted over seawater versus rocky ground, the far-field
> elevation pattern low-angle radiation increases.
> Question E9C17 - answer - The main effect of placing a vertical
> antenna over an imperfect ground is that it reduces low-angle
> Also, on the audio study guide, Gordo makes some stray comments
> about using 3 inch copper strap for radials on his roof, and
> mentions improving the ground field increases low angle
> radiation - he goes on to say it does not increase signal strength,
> of course, but only that it increases the amount of signal that
> has low take off angle.
> This information is consistent with all that I have read on verticals
> in the ARRL Antenna Handbook, and I did LOTS of research before
> installing a large vertical monopole in the back yard.
> A huge ground pane does lower take off angle (as NEC modeling
> shows) and also improves antenna efficiency -- I stopped at 65 radials
> but I wish had installed even more just to be sure. Also, my back yard
> soil is very conductive and remains moist even through the summer, so
> the soil, itself, helps me considerably. Rob Sherwood and I exchanged
> some nice email at the time I was doing this homework, and I believe
> he lives over a more dry, rocky soil, and that is much harder to work
> over. I also corresponded with the infamous Rudy Severns N6LF
> and his findings are consistent with this conclusion. NEC modeling
> produces consistent results.
> N'est ce pas? Happy trails OM.
> =============== JHR ============================
> I had
> On 1/5/2011 1:01 PM, Steve Hunt wrote:
>> I presume the "wink" indicates that is a joke !
>> The only thing that would improve the elevation pattern would be
>> improved ground conditions in the Fresnel Zone where the ground
>> reflections are taking place. That would take some awfully long radials
>> - certainly well beyond my property boundary - and an awful lot of them
>> to achieve a copper density that would affect the conductivity so far out.
>> Steve G3TXQ
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