I wonder what happened to my last post with questions to Richard Harrison.
I don't see it. Boy! I'm not doing well at all on this Usenet thing
today.....

Comments inserted below.


--
Steve N, K,9;d, c. i My email has no u's.

"Walter Maxwell" wrote in message
news
On Fri, 05 Mar 2004 21:50:55 -0600, Cecil Moore

wrote:

wrote:
Non-dissipative resistance is not well accepted or understood by
many otherwise well informed engineers...no ...treatment in EE courses.

On Sat. 06 Mar 2004 Cecil Moore wrote:

Yet the IEEE recognizes those two types of resistances with different
definitions.
Definition (A) talks about "dissipation or other permanent loss".
Definition (B) simply says "The real part of impedance."
Then a note: "Definitions (A) and (B) are *NOT* equivalent ..." (emphasis
mine)

The resistance in a resistor satisfies definition (A). The characteristic
impedance of a transmission line satisfies definition (B).

What you said above is true, Cecil, but one more statement applies to
Definition B). Although Definitions (A) and (B) are not equivalent,
Definition (B) does include the real part of the impedance of a
dissipative resistor.
The only way to tell which is which is to determine which develops heat.

I still maintain that many otherwise well qualified engineers not aware of
Definition (B), and therefore reject the concept of a resistance that
doesn't dissipate power. And this applies to much more than the Zo of
transmission
lines.


I consider myself very well qualified and have no problem with both
of these conditions and believe I understand them fully. (my post of
questions to Richard Harrison would show, if I could see it--wonder if I
didn't push the send button)

I can only say that I have never heard the term "non-disipative
resistance" either professionally or in the hobby. It is not taught. If I
had to say why, it is because it is a self-conflicting term. In my
nomenclature, all "resistance" dissipates power as heat. In other words,
resistance is what resistors have. Resistance can produce the real part of
an impedance, but the real part can come from other things.
In other situations such as the T-Line, there is a "real part" to
the impedance. The Engineer understands that this is due to a combinatin of
physical things, not only a resistor, so the term in question refers to
something that the Engineer does not need to discuss. When there is only
a real part (no reactance), then both are indistinguishable to the source --
so from the source's point of view, they are the same. In the bigger
picture, however, there is a difference -- heat vs. power going elsewhere.
However, I do not believe it is a good term (loss-less resistance) to use in
this case.
I would call it an unnecessary complication to add a new term of
"loss-less resistance" when you understand all of this. If you were to have
a term "loss-less real part", then I'd say you have a more accurate
technical term. Although, the Engineer (by this, I mean both me and those I
have discussed circuit concepts in school and professionally) knows what is
underdiscussion and what the impedance is and where it comes from, so a new
term is unnecessary.
I don't know if this helps, but it really seems to be adding a term
or name when it is not necessary.

So while the term may "work" for some people, I believe it is a
slight mis-use of the term "resistance".
When you first start talking about "loss-less resistance" to a
schooled Engineer, he'she gets the wrong idea as to just what you are
talking about since it is a conflict in terms.
--
Steve N, K,9;d, c. i My email has no u's.



And because there still remains many who believe the RF power amplifier
absorbs
and dissipates reflected power, I chose to try again to dispel that notion
in my
post in the 'max power theorem' thread.

Walt Maxwell, W2DU