[Elecraft] : Resonance

[Guy Olinger, K2AV]

> I was always of the impression that the definition of resonance of a
> half wave radiator is the condition in which the current at the center
> is a maximum and the current at the ends is at zero.

This would also be true of a 1/4 wave dipole fed in the center, or any 
dipole less than a 1/2 wave.  The current would be higher in the center of a 
less than 1/2 wave dipole, than it would be for the same power fed to the 
center of a 1/2 wave dipole. No one to my knowledge considers a 1/4 wave 
dipole "resonant".

I'm not aware of any standard reference that does not define as resonant a 
1/2 wave dipole having zero reactance at a center feed. The classic Terman's 
shows overall circuit current at "resonance" as being entirely resistive. 
{p.46, Electronic and Radio Engineering 4th Edition, F E Terman, McGraw 
Hill, 1955}

For the dipole this would be the point that the undissipated power from 
prior excitation returns exactly in phase with incident excitation.  This is 
your grid dip meter case of maximum accepted power, hence maximum dip, and 
also where a center feed displays zero reactive current.

Perhaps a better definition of a wire resonant at a given frequency would be 
*if there exists* a point on the wire where a feed so placed would not 
exhibit any reactance. This takes in other cases than center fed 1/2 wave 
dipoles.

73, Guy.