From: John Rabson <john.rabson@numeo.fr>
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Date: Tue, 27 Jul 2010 16:53:00 +0200
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Subject: Re: LF: David Gibson on Earth antennas and propagation below 9 kHz
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Andy,

I hope to be doing some aerial  experiments (yes - above ground not below)=
 in the next few weeks and will see if I can put something up and do some=
 measurements.

73
John F5VLF

On 26 Jul 2010, at 16:09CEST, Andy Talbot wrote:

> I was thinking about this, and thoughts turned to a rather simpler anten=
na;  the folded dipole and how it would behave when electrically short.
> =20
> A simple non-folded  electrically short dipole (negelecting all losses)=
  has Rin proportional to 1/L^2 and a highly capacitive reactive term
> =20
> A folded half-wave dipole fed conventionally has Rin about 4* that of a=
 normal dipole due to current sharing in the legs -.
> =20
> Now the conumdrum - what does an electrically short folded dipole look=
 like?     It has got to be inductive, since we're feeding into a squashed=
 shorted turn, and presumably the current distribution looks short dipole-=
ish.
> =20
> So is it a loop, is it a dipole, is it both, how can it be both, if it=
 is what's its radiation pattern ?
> Similar to the ground loop/dipole question ?
> =20
> And is there a length where the inductance of the loop bit resonates wit=
h the capacitance that 'ought' to be there due to its also being a short=
 dipole.
> =20
> ?????????????????????????????????????
> =20
> Andy
> www.g4jnt.com
> (not really an antenna sort of person)

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<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Andy,<div><br></div><div>I hope to be doing some aerial &nbsp;experiments (yes - above ground not below) in the next few weeks and will see if I can put something up and do some measurements.</div><div><br></div><div>73</div><div>John F5VLF</div><div><br><div><div>On 26 Jul 2010, at 16:09CEST, Andy Talbot wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div>I was thinking about this, and thoughts turned to a rather simpler antenna;&nbsp; the folded dipole and how it would behave when electrically short.</div>
<div>&nbsp;</div>
<div>A&nbsp;simple non-folded &nbsp;electrically short dipole (negelecting all losses)&nbsp; has Rin proportional to 1/L^2 and a highly capacitive reactive term</div>
<div>&nbsp;</div>
<div>
<div>A folded half-wave dipole fed conventionally has Rin about 4* that of a normal dipole due to current sharing in the legs -.</div>
<div>&nbsp;</div></div>
<div>Now the conumdrum - what does an electrically short folded dipole look like?&nbsp;&nbsp;&nbsp;&nbsp; It has got to be inductive, since we're feeding into a squashed shorted turn, and presumably the current distribution&nbsp;looks short dipole-ish.</div>

<div>&nbsp;</div>
<div>So is it a loop, is it a dipole, is it both, how can it be both, if it is what's its radiation pattern ?</div>
<div>Similar to the ground loop/dipole question ?</div>
<div>&nbsp;</div>
<div>And is there a length where the inductance of the loop bit resonates with the capacitance that 'ought' to be there due to its also being&nbsp;a short dipole.</div>
<div>&nbsp;</div>
<div>?????????????????????????????????????</div>
<div>&nbsp;</div>
<div>Andy<br><a href="http://www.g4jnt.com/">www.g4jnt.com</a> </div>
<div>(not really an antenna sort of person)<br></div></blockquote></div><br></div></body></html>

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