Actually, several people (W8JI among them) have measured the output
impedance of common amateur linear amplifiers by at least a couple of
methods. The most credible measurements show, interestingly, a value
very close to 50 ohms when the amplifier is adjusted for normal operation.

[sotto voce] "and yet it moves" - updated to

Of course, it doesn't really matter, but people continue to make a big
deal out of it.

Roy Lewallen, W7EL

On Wed, 15 Oct 2003 06:48:09 -0500, Cecil Moore
wrote:

Richard Clark wrote:
A transmitter is loaded with two components and a meter placed between
them - woohah!

Richard, I've got Chipman's book now. Where does he say that SWR
depends upon the source impedance. He does describe a localized
resonance effect within a transmission line. Are you saying the
source impedance is a causal parameter for that localized resonance
effect?

Not arguing with you - just still trying to understand what you
are saying.

Hi Cecil,

Your "not arguing" is as passive as your not looking at either the
text nor referencing my having answered this time and time befo

Chapter 3. Fig. 3-1 "Complete transmission line circuits"

Chapter 3. Fig. 3-2 "Equivalent circuits"

These may be resourced to the SAME answers to you Oct. 3.

Also introduced to you:

Chapter 4. Section 4.4 "Reflected Waves"
which describes the commonplace that any line terminated in an
impedance not the same as the characteristic of the line produces
reflections. This, of course, is something that you have no differed
upon, but on the same hand, neither have your carried it to its
logical conclusion which this section introduces as material being
prepared for Chapter 8. Also note that this section explicitly
references the figures described above.

The cogent point offered by Chipman (and has been reported here by me
as a quote), that when a reflection occurs at the load and returns to
the source:
"in general will be partially re-reflected there, depending on
the boundary conditions established by the source Impedance Zs."
It should come as no surprise that this combination of source power
and re-reflected power will produce a resultant that is dependant upon
the length of the line. This conforms to the simple mechanics of
interference which has been so ill-abused here.

Also quoted he
Chapter 8. Section 8.2 "The practical importance of standing
wave observations."
where in paragraph (e)
"... when the source impedance is not equal to the characteristic
Impedance of the line, this conclusion does not apply. The
General case is discussed more fully in Chapter 9."

Then of course there is more in Chapter 8
Chapter 8. Section 8.8 "Multiple Reflections."
This material shows the transient analysis and sets up the steady
state analysis already anticipated above in Chapter 9.

Chapter 9. Section 9.10 "Return loss, reflection loss, and
transmission loss."

This gives an equation (which modelers fail to appreciate in lesser
work) that answers my earlier Challenge of how to reveal the
Transmitter's characteristic Z through the measure of line loss due to
mismatch at both ends of the line.

Chapter 10. Section 10.7 "Resonance curve methods for impedance
measurement."

This offers how the voltage variation ALONG a transmission line is
function of BOTH source Z and load Z. This was demonstrated by my
bench example. Roy wanted that expressed as a formula specific to
SWR, but as he stated he wasn't going to have his mind changed, I
deemed it unnecessary to extend the math to perform that chore, and
especially when this assemblage of Chipman's work is both unread, and
when offered in recitation is unresponded to. Such is the quality of
"peer review."

Chipman is but a single source that I have offered, but he does have a
following and his material is written to be accessible.

As I have stated, my advantage is that I could be proven wrong by my
interpretation, but none choose to do so with their own readings from
the same source.

The question that remains:
Do you abandon the topic like the others?

73's
Richard Clark, KB7QHC