Re: LF: David Gibson on Earth antennas and propagation below 9 kHz

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Subject:	Re: LF: David Gibson on Earth antennas and propagation below 9 kHz
From:	Andy Talbot <[email protected]>
Date:	Mon, 26 Jul 2010 15:09:53 +0100
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I was thinking about this, and thoughts turned to a rather simpler antenna; the folded dipole and how it would behave when electrically short.

A simple non-folded electrically short dipole (negelecting all losses) has Rin proportional to 1/L^2 and a highly capacitive reactive term

A folded half-wave dipole fed conventionally has Rin about 4* that of a normal dipole due to current sharing in the legs -.

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.

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 ?

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 a short dipole.

?????????????????????????????????????

Andy
www.g4jnt.com

(not really an antenna sort of person)

On 21 July 2010 08:12, John Rabson <[email protected]> wrote:

Reposted by permission

John F5VLF

The antenna is a "horizontal end-grounded line current" antenna; commonly referred to as a "horizontal end-grounded electric dipole". The word "dipole" is often used a bit too loosely, although that is a moot point. If you think "horizontal electric dipole" you get the general idea: its an electric dipole, not a loop antenna.

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