50 Ohms "Real Resistive" impedance a Misnomer?
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July 15th 03, 05:46 PM
On Tue, 15 Jul 2003 10:22:02 -0500 (CDT),
(Richard Harrison) wrote:
Dr. Slick wrote:
"The funny thing about this is that you cannot say that the 50 ohms in
the center of the chart is a "resistive" 50 ohms as there is very little
real resistance in the average antenna."
This is seems to be a point of convergence for the derivation of many
fascinating and strange theories of fancy and speculation.
You point out in the remainder of your posting about the combination
of resistances (giving particular care to describe in terms of phase)
and yet many posters here fail to account for those same assortment of
R's available from real life.
One notable offering of measuring antenna (or load) impedance involved
the use of a thermometer to which I asked "what is the Z for a 1
degree rise?" I was not surprised to find no answer forthcoming even
when the premise was sound. Such is the shortfall of speculation in
the face of analytical enquiry. There is no corresponding shortfall
of opinion draped in the mantle of citations unfortunately.
These attempts to separate "real" resistance from other resistances
are challenged with volumes of formulaic recitation, and the absolute
resistance (yet another meaning) to merely stepping out into the field
with an OhmMeter (much less that same thermometer). Clearly,
resolution of these imponderables is not a target for some scribblers.
For many years there has been this effete distinction of there being
dissipative and non dissipative resistance (perhaps the basic, or
elemental concern of this thread; yet through hazy writing that agenda
remains elusive). The transmitter cannot possibly separate the two.
It thus remains for the target audience to resolve, but even they
cannot either unless the incident of gaining or losing this additional
resistance occurs in a short enough interval to allow its perception
(notably expressed in dB). If the researchers refuse to do some field
work, it will always remain among their mysteries of the sacrament.
Richard Clark, KB7QHC
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