[TowerTalk] Resonance is over rated
Andy
ai.egrps at gmail.com
Fri Aug 7 20:37:23 PDT 2009
> Something either has capacitive or inductive reactance, both not both at
the
> same time.
That is true of the total net reactance. Antennas in general do have both,
distributed along their elements; as do tuned circuits; but when you look at
the terminals, you see only the net reactance which is one or the other.
Maybe a better definition is that a device ought to have a reactance that
varies with frequency, which goes through zero and is capacitive on one side
and inductive on the other. That would preclude purely resistive devices.
This concept of resonance also gets clouded when looking at the input
terminals of your feedline. Unless the resonant impedance happens to equal
the feedline's characteristic impedance (or the feedline is an exact
multiple of a half wavelength), you'd find that the impedance seen in the
shack looks resonant at an entirely different point. By not concentrating
so much on resonance, you don't need to think about which resonance would be
the "right" one.
Andy
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