[Elecraft] : Resonance

[Stephen W. Kercel]

Guy:

Interesting points.

73,

Steve
AA4AK


Guy Olinger, K2AV wrote:
>> 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.
>
>