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."

Resistance is defined as real. That is, current is instantaneously
proportional to the voltage.

Any efficient antenna has a high ratio of radiation resistance to loss
resistance.

Resistance is the ratio of in-phase voltage to current accepted by an
antenna. Part is made by loss in the antenna. part is made by radiation
from the antenna. They are often represented by an equivalent circuit of
two resistors in series.

Dr, Frederick Emmons Terman says of radiation resistance:
"This is the resistance that, when inserted in series with the antenna,
will consume the same amount of power as is actually radiated. ---it is
customary to refer the radiation resistance to a current maximum in the
case of an ungrounded antenna, and to the base of the antenna when the
antenna is grounded."

Best regards, Richard Harrison, KB5WZI

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."


Hi Richard,

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.

73's
Richard Clark, KB7QHC

(Richard Harrison) wrote in message ...
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."

Resistance is defined as real. That is, current is instantaneously
proportional to the voltage.

Any efficient antenna has a high ratio of radiation resistance to loss
resistance.



Ok, i stand partially corrected. I should have stated this:

"You cannot tell if the 50 Ohms reading on a Network analyzer into
a Black Box is a dissipative resistance like a dummy load, or if it is
a radiated resistance of a perfectly matched antenna. You don't have
that information."

Richard, I like your definition of real: "Resistance is defined
as real. That is, current is instantaneously proportional to the
voltage."

In other words, the V and I sine waves will be IN PHASE.

This clarifies it more for me. BOTH the radiation resistance and
the dissipative resistance of a dummy load are both "real" resistive
impedances.


Thanks,

Slick

Dr. Slick wrote:
"You cannot tell if the 50 Ohms reading on a Network analyzer into
a Black Box is a dissipative resistance like a dummy load, or if it is
a radiated resistance of a perfectly matched antenna. You don't have
that information."

Conversion of RF energy to heat can be measured. Conversion of RF energy
to EM radiation can be measured.
--
73, Cecil http://www.qsl.net/w5dxp



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W5DXP wrote in message ...
Dr. Slick wrote:
"You cannot tell if the 50 Ohms reading on a Network analyzer into
a Black Box is a dissipative resistance like a dummy load, or if it is
a radiated resistance of a perfectly matched antenna. You don't have
that information."

Conversion of RF energy to heat can be measured. Conversion of RF energy
to EM radiation can be measured.


Agreed. But a Black Box to me implies you have limited
information from it. My point is that if someone gives you an
impedance plot of a resistive 50 Ohms, you will not be able to tell if
it is dissipative (lossy) or radiated resistance.

I was just reading that Joseph Carr calls radiated resistance as
a sort of "ficticious" resistance. I'm sure many here would argue
this description, but it kinda makes sense to me.


Slick

I'd be one of the people arguing. Radiation resistance fits every
definition of resistance. There's no rule that a resistance has to
dissipate power. The late Mr. Carr was quite apparently confusing
resistance with a resistor, a common mistake.

Why not call radiation resistance "real" resistance and loss resistance
"ficticious"? Makes just as much sense as the other way around -- that
is to say, none.

Roy Lewallen, W7EL

Dr. Slick wrote:
W5DXP wrote in message ...

Dr. Slick wrote:

"You cannot tell if the 50 Ohms reading on a Network analyzer into
a Black Box is a dissipative resistance like a dummy load, or if it is
a radiated resistance of a perfectly matched antenna. You don't have
that information."

Conversion of RF energy to heat can be measured. Conversion of RF energy
to EM radiation can be measured.



Agreed. But a Black Box to me implies you have limited
information from it. My point is that if someone gives you an
impedance plot of a resistive 50 Ohms, you will not be able to tell if
it is dissipative (lossy) or radiated resistance.

I was just reading that Joseph Carr calls radiated resistance as
a sort of "ficticious" resistance. I'm sure many here would argue
this description, but it kinda makes sense to me.


Slick

Roy Lewallen wrote in message ...
I'd be one of the people arguing. Radiation resistance fits every
definition of resistance. There's no rule that a resistance has to
dissipate power. The late Mr. Carr was quite apparently confusing
resistance with a resistor, a common mistake.


Your point has been well taken, Roy. But you have to admit that
radiation resistance is not a easily understood concept (which is why
it may be a common mistake), so for someone to call it a "fictitious"
resistance can make sense, in the sense that it is not a dissipated
resistance. After all, "Imaginary" numbers are well accepted. And
from an arguing sematics point of view (which is unfortunately
necessary sometimes), even you call it "radiation resistance", which
means that it is obviously not the same thing as a dissipative
resistance like a 50 Ohm resistor.

That being said, rest assured, Roy, that you have convinced me!



Slick

Roy Lewallen wrote in message ...
I'd be one of the people arguing. Radiation resistance fits every
definition of resistance. There's no rule that a resistance has to
dissipate power. The late Mr. Carr was quite apparently confusing
resistance with a resistor, a common mistake.


BTW, did Joseph Carr really pass away? Sad, his book is very practical.


Slick

Yes, he died not long ago, within the last year I believe.

Roy Lewallen, W7EL

Dr. Slick wrote:
Roy Lewallen wrote in message ...

I'd be one of the people arguing. Radiation resistance fits every
definition of resistance. There's no rule that a resistance has to
dissipate power. The late Mr. Carr was quite apparently confusing
resistance with a resistor, a common mistake.



BTW, did Joseph Carr really pass away? Sad, his book is very practical.


Slick