[Antennas] ground mounted vertical radials question

Saandy Eban alexeban at gmail.com
Wed Nov 15 10:45:05 EST 2006 

...guys, there's a big difference between a workable antenna and a   GOOD
antenna. A workable may get along with 2 radials per band, but it's hardly
enough! You only get a reasonable SWR but a lot of losses too. 
If ground mounted, you need many radials to create a conductive mat under
the antenna, not in order to realize a counterpoise. You guys tend to
intermingle operation with radials with operation with a ground plane! These
are 2 different mechanisms!
Antennas on ground planes don't rely actually on the length of the ground
wires; they merely use them to provide the return path for the field induced
currents. Radials, on the other hand radiate: they are a part of the antenna
itself. This can be proven by playing with the slant angle of the radials:
when spread in an horizontal plane the input impedance is 36 ohms as for a
ground plane. When dropping vertically underneath the antenna, you get 72
ohms, as in a dipole.
Definitely something else: one is BASED on the "radials" being 0.25
wavelengths and one who couldn't care less what length they are, as long as
the ground capacitance is enough and the gathering of the field induced
current is reasonably good enough.
Doctor, leave the poor mathematics alone, get physical. OBSERVE! There are
too many variables for calculation: some areas cope very well with two
radials, some need 100. You don't even have to calculate: think what will
happen if you have a copper plate backyard!! I should do just that, since I
live over sand, here, in 4Zulu land!
Just put in all you can and enjoy that: nobody can do more!



Alex Eban     4Z5KS
alexeban at gmail.com
      050-7774300
      03-9067913




-----Original Message-----
From: antennas-bounces at mailman.qth.net
[mailto:antennas-bounces at mailman.qth.net] On Behalf Of Charles Greene
Sent: Wednesday, November 15, 2006 4:52 PM
To: Dr. William J. Schmidt, II; David Ashworth; antennas at mailman.qth.net
Subject: Re: [Antennas] ground mounted vertical radials question

Bill,

Who do you want me to quote, W2FMI or ON4UN?.  What measure of 
evaluation?  Increase of 0.2 dB in the far field?  Why not 1.0 dB, or 
even 3 dB?  Who is going to notice 1/2 an S unit, particular with QSB 
over 10 dB?   As I don't want to get into a flaming contest,  this 
will be my last communication on the subject.

I agree on this: add radials until the ground resistance essentially 
stops decreasing.

73,  Chas

At 11:54 PM 11/14/2006, Dr. William J. Schmidt, II wrote:
><<Using more than 16 radials does not help much.>>
>
>Prove this....  Show me mathematically how this makes any sense.
>
>Sincerely,
>
>Dr. William J. Schmidt, II  K9HZ
>Trustee of the North American QRO - Central Division Club - K9ZC
>
>Email: bill at wjschmidt.com
>WebPage: www.wjschmidt.com
>
>"If you drink... don't drive.  Don't even putt"  - Dean Martin.
>
>
>----- Original Message ----- From: "Charles Greene" <crgreene at cox.net>
>To: "David Ashworth" <fathom at dslextreme.com>; <antennas at mailman.qth.net>
>Sent: Tuesday, November 14, 2006 8:34 PM
>Subject: Re: [Antennas] ground mounted vertical radials question
>
>
>>David,
>>
>>The best approach is to go for more radials on the order of 0.1 
>>wavelength rather than less radials that are longer.   I have a 
>>Hustler 6BTV and I put 2 radials for each band about a 1/4 wave 
>>length each; however, that was several years ago and I'm smarter 
>>now.  So if a radial is 0.1 wavelength on 80, it is 0.2 wavelength 
>>on 40, 0.4 wavelength on 20 and so on so it is an effective length 
>>on all bands.  The reason for this is that current in the ground 
>>radial drops off over 0.1 wavelength so making the wire longer  is 
>>not necessary, but the longer wire does not degrade the effect of 
>>the radial, so the longer wires are still an effective length. You 
>>would think 1/2 wavelength would not be a good length as it would 
>>ofer a high impedance at the antenna, but looking at the current 
>>that is not the case.  Using more than 16 radials does not help 
>>much.  In other words, 32 radials marginally better than 16, but 
>>not twice as good.
>>
>>
>>73,  Chas W1CG
>>
>>At 12:37 AM 11/11/2006, David Ashworth wrote:
>>>Hello to all.  Will be installing a Hustler 5BTV vertical on the ground,
up
>>>in the country where there is no problem with people tripping over
radials.
>>>The radials will NOT be buried.  They will be placed upon the ground.
Been
>>>reading my reference material on radials, but would like to hear from
>>>operators that have been there/done that.  The lowest band will be 80
meters
>>>and the highest 10 meters.   Hustler recommends at least two radials per
>>>band.  Then, been reading W2FMI's book about short verticals.  Think he
was
>>>happy with about 40 radials.  Am I on the right track, the more radials,
the
>>>better, up to a certain point?  The soil there is very dry unless it has
>>>been raining.  As soon as the sun comes out, there goes the moisture
content
>>>of the soil.  So, would it be better to spread, say 40 radials at 1/8
>>>wavelength, or maybe 20 at 1/4 wavelength?  Would you spread some for
just
>>>80, or do a combination of the different bands?  If this was salt water,
bet
>>>you could throw a coat hanger in there, but it is not.  Any good ideas?
I
>>>am leaning towards less radials and longer radials, but experience is the
>>>best teacher.  Thank you for your comments/recommendations, Dave, NC6P.
>>>
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>>
>>
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>


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