[TowerTalk] Feedpoint Impedance

jimlux jimlux at earthlink.net
Tue Jul 29 09:59:37 EDT 2008

Ward Silver wrote:
>> Radiation resistance should be fixed..
> Oh, right...duh.
> The current equation will do - but the radiator (I may have confused things 
> by referring to it as a "dipole") may be anywhere between one-half and one 
> wavelength long, so the current won't be a simple cosine function.  It 
> *will* be zero at the ends :-)

(unless you run a lot of power, and have corona discharge <grin>)

I think Orfanidis's book has the equation you're looking for.. actually 
several approximations, of varying fidelity..

I'm pretty sure there's some standard assumptions of the current 
distribution shape (ranging from uniform for very short, to triangular 
to sinusoidal to something else), possibly broken up into segments.

What sort of accuracy are you looking for?


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