On Jul 1, 11:14 pm, Cecil Moore wrote:
Keith Dysart wrote:
On Jul 1, 4:35 pm, Cecil Moore wrote:
Richard Harrison wrote:
Radiation resistance is a resistance. Radiated energy has its current
in-phase with its voltage.
The IEEE Dictionary is pretty clear when they define two
types of resistances: (A) a resistor with resistance and
(B) a virtual resistance with the V/I ratio in phase.

I could not find "virtual resistance" in "IEEE 100, The Authoritative
Dictionary of IEEE Standards Terms, Seventh
Edition".

Do you have a reference?
Sure do, Keith - your own quote. An example of Definition
(A) is a resistor. An example of Definition (B) is the
characteristic impedance of a transmission line which
is a virtual dissipationless resistance. Another example
of (B) is the feedpoint impedance of a standing wave
antenna. Another example of (B) is the virtual impedance
at the end of a quarter-wave series section transformer.
Another probable example of (B) is the dissipationless
part of a generator's source impedance.

I understand now. "Virtual resistance" is a term of your
own invention, not the IEEE, which explains why it is not
in the dicionary.

It is not a bad term for the concept, just misattributed.

....Keith

Keith Dysart wrote:
I understand now. "Virtual resistance" is a term of your
own invention, not the IEEE, which explains why it is not
in the dicionary.

I didn't invent the term, Keith. It is simply
descriptive of a resistance when the resistance
is not a resistor - a virtual resistance as
opposed to a physical resistor.

The fact that there are two definitions, (A) and
(B), for resistance in the IEEE dictionary is what
is important. But their definition has (A) as a
subset of (B). So what do we call a resistance that
satisfies the (B) definition but not the (A) definition?
Walter Maxwell calls it a virtual resistance and that's
good enough for me.

It is not a bad term for the concept, just misattributed.

I believe the first time I encountered the word
"virtual" used for an impedance was when I read
Walter Maxwell's early QST articles some 30 years
ago.
--
73, Cecil http://www.w5dxp.com