TopBand: Radial current

[Bob Wruble]

the article was in communications qtrly by k5iu and contributions
and tests at jay, wx0b qth in dallas......good article and picked up
the rag at dayton rag seller booth   w7gg

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> From: Larry Tyree <n6tr@teleport.com>
> To: topband@contesting.com
> Subject: TopBand: Radial current
> Date: Wednesday, June 04, 1997 11:17 AM
> 
> 
> Gee - I had been feeling pretty good about my antenna system...
> 
> That was - until W0UN sent me a copy of a recent article he saw.
> 
> It seems likely that my 20 elevated radials aren't all equally sharing the
> current.  This article (sorry - I left it at home and forget who
> to credit as writing it) simply shows that if any one of the radials
> is near zero impedance (electrically a quarter wave) that the lion's
> share of the current will go into that radial.  
> 
> Compare the current into a zero ohm resistor and a 2 ohm resistor 
> and it becomes clear.
> 
> As you change frequency, the distribution of current in the
> radials will change as a different one approaches the right length.
> 
> The article also provides some solutions.  The simple approach appears
> to be to either shorten or lengthen all of the radials by a quarter
> wavelength (or something close to that).  Now, you will have impedances
> that still may vary by a few ohms, but none of them are near zero
> Ohms.  Then use some loading to tune the radial system for the desired
> frequency (using an inductor if they are short, or a capacitor in series
> if they are long).
> 
> This seems to make a lot of sense - and all from using nothing more
> complicated than Ohm's law.  
> 
> The advantages are a better pattern because of more uniform current
> flow.  The other advantage is elimination of a possible horizontal
> polarized component because of unequal distribution.  I didn't think
> of that before, but having symetric current flow around the base
> of the antenna is important in this regard.  It would also follow 
> that I need to be careful about the physical distribution of the 
> radials as well.  Currently, I have a higher concentration in 
> some directions (i.e., Europe and the east coast).
> 
> So - I guess I will cut my radials down in length (perhaps to 3/16 wave)
> and put an inductor in series with them and adjust it for minimum 
> impedance on 1825 kHz.  Perhaps I will make some current measurements
> before and after to verify the results.  I could tune each radial 
> individually to make them all the same impedance at 1825 before 
> connecting them in parallel.
> 
> Of course, this will remove all the magic from the system and it 
> will never work the same...  
> 
> Been trying a few CQs around 0500Z looking for a ZS or something,
> but no luck yet.  Received a QSL from HP3FL yesterday.  
> 
> 73 Tree N6TR
> tree@contesting.com
> 
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