On Mon, 2008-07-07 at 14:52 -0700, Alfred Lorona wrote:
> Zero reactance in a wire antenna feedpoint is a necessary but not sufficient
> condition for it to be truly resonant. Citing the Antenna Fundamentals, chap
> 2, page 2-1 of my 16th addition of The ARRL Antenna Book, a resonant wire is
> defined as 'The shortest length of wire that resonates at a given frequency
> is one just long enough to permit an electrical charge to travel from one
> end to the other and back in the time of one RF cycle.'
That limits a resonant antenna to those without any loading. That
definition is too narrow because of that.
> Clearly, a short wire with a finite pure resistive radiation impedance is
> too short physically for the required condition to exist as stated in the
> Handbook definition..
So having a resistive feed Z by adding a loading coil to a short wire is
not resonant. I disagree.
> On the other hand, elsewhere in the book, a zero reactance 'resonant'
> condition does not mention the required physical length of the wire.
Perhaps because that is allowing for loading coils and/or trimming
> If this
> is all that is required, ANY wire can be called resonant and there is
> nothing to distinguish such wires from a halfwave wire.
Not so, because if loading coils or trimming capacitors are not allowed
the only way a wire can have resistive feed point impedance is for that
wire to be a multiple of 1/4 wave long, or there is no wire, only a
> Somehow this doesn't
> sit right with me. What do you think? Do you think that this discrepancy
> begs for a minor clarifying rewrite?
> 73, AL
73, Jerry, K0CQ
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