Bob,

Sorry for the strong words, but the intent remains the same.

I don't know what happens to the source impedance when the load is
changed, because the system is undefined.

However, read carefully the definition at the beginning of your paper.

The Maximum Power Transfer Theorem:

The maximum power will be absorbed by one network from
another joined to it at two terminals, when the impedance of
the receiving network is varied, if the impedance looking into
the two networks at the junction are conjugates of each other
[1]

Gene Fuller wrote:
"I don`t know what happens to the source impedance when the load is
changed, because the system is undefined."

Yes. Maximum power transfer is accomplished by making the load impedance
the conjugate of the generator impedance as defined by Thevenin`s
theorem.

The value of the Thevinen impedance is that which might be measured by a
generator`s open-circuit voltage devided by its short-circuit current.
You don`t need to know the generator`s specifics other than, drop in the
output voltage is proportional to the current delivered.

The current which flows in a linear load impedance connected to a
Thevenin generator is the open-circuit voltage divided by the sum of the
generator`s internal impedance and the load impedance. These may be
complex impedances.

At maximum power transfer, internal and load impedances are equal in
resistance and their reactances are conjugate (opposite and equal).

There is no requirement that resistance in either the generator or load
be dissipative, and frequently, lossless resistance is a part of the
generator impedance so that we can get maximum possible power into the
load without losing 50% in the generator.

Best regards, Richard Harrison, KB5WZI

On Tue, 02 Mar 2004 15:37:25 GMT, Gene Fuller
wrote:

Bob,

Sorry for the strong words, but the intent remains the same.

I don't know what happens to the source impedance when the load is
changed, because the system is undefined.

However, read carefully the definition at the beginning of your paper.

The Maximum Power Transfer Theorem:

The maximum power will be absorbed by one network from
another joined to it at two terminals, when the impedance of
the receiving network is varied, if the impedance looking into
the two networks at the junction are conjugates of each other
[1]
.
.
.
[1] W. L. Everitt, "Communication Engineering", McGraw-Hill, 1937

The maximum power transfer theorem describes the impact from change of
the load impedance. It is not the Grand Unified Theory for all the
universe. If someone tries to expand this elegant concept to all sorts
of pathological cases then it is likely that confusion will ensue.

The MPTT analysis is straightforward if the problem is well defined. The
ongoing argument in amateur radio circles is about the source
characteristics of amplifiers and tank circuits. The MPTT does not
address that argument, but rather it is a victim of the silliness.

Including the down-home touch of steam engines adds nothing to the
technical content.
Dear Gene,

No problem, I will try to understand where you're coming from.
Obviously, there have been some experiences in your tour of duty that
have caused you some heartburn - it happens with all of us.

Relative to your points about amplifiers, etc., I hope to have my
article on that topic available before the end of this month.
Actually, it has been "almost ready" for several days now, but there
are some things that need to "cook" awhile before I release it. As
soon as you get into the details of a Class-B linear, you're up to
your butt in alligators, not to mention all of the myths surrounding
them and the matching problem. I'll do my best to keep it "on topic" -
Hi!

73,
Bob

From the design side, MPTT is defined at an interface, and minimizes
"reflected power" at that interface, and that is it.

The other items about matching are also quite important, such as stability,
loading, impedance transfer (both directions), bandwidth, Qs, loaded Qs etc.
But that is Not MPTT. There is a tradeoff between these, if one can also
obtain mptt, great, but close is good too.

mptt is just one of several parameters needed to optimize a match. At times
there are too many unknowns and the matching is experimental (class C)
.................................................. ...........................
........................
"Robert Lay W9DMK" wrote in message
...
On Mon, 01 Mar 2004 22:23:56 GMT, Gene Fuller
wrote:

What a load of crap!

The only difficulty in the MPTT occurs when some folks create new
definitions and new constraints that are not shared by others in the
discussion. Allowing the problem to float at will means that the
solutions will float as well.

The longstanding MPTT argument in amateur radio circles is not really
about power transfer and conjugate matching. The argument is typically
about what happens to the source impedance under varying load conditions.

Steam engines? Gear boxes? Yeah, sure, they help a lot.

That's a fair question, Gene - what does happen to the source
impedance under varying load conditions?

While you're at it, could you please explain how you would separate
the issues of maximum power transfer and conjugate matching from the
question of what happens to the source impedance under varying load
conditions?

I have no problem in supplying copies of the article to anyone who
requests a particular format by e-mail - available choices are pdf,
html, or Word for Windows 97 or 2003. The complete file is
approximately 1 MB in any of the formats.

73,
Bob

"John Smith" said -
MPTT is defined at an interface, and minimizes
"reflected power" at that interface, and that is it.

===============================

Indeed it is. R+jX one way and R-jX the other.

Why the vast amount of palaver and bickering about such an obvious and
elementary notion defeats the imagination.

Reg Edwards wrote:
Indeed it is. R+jX one way and R-jX the other.

Why the vast amount of palaver and bickering about such an obvious and
elementary notion defeats the imagination.

Reg, you are in a room with a transmission line passing through it.
You measure all voltages, currents, and powers. How do use your "obvious
and elementary notions" to tell if the transmission line is conjugately
matched or not? How do you measure the impedance looking toward a typical
amateur radio transmitter without changing the very thing you are trying
to measure? Many have tried and many have failed.
--
73, Cecil http://www.qsl.net/w5dxp



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Check for reflected power in either direction.
If none, then it is conjugally matched exactly.
If it is about -14 dB down, that is good and close enough.

One can try to measure Tx output Z (looking into Tx) and then the Z looking
backup the antenna line, and try matching the two as a start,
but reflected power quicker, faster, more accurate.
(also I agree with you in trying to measure Tx output Z (looking into the
output)
tried and got a mess many times,...)


"Cecil Moore" wrote in message
...
Reg Edwards wrote:
Indeed it is. R+jX one way and R-jX the other.

Why the vast amount of palaver and bickering about such an obvious and
elementary notion defeats the imagination.

Reg, you are in a room with a transmission line passing through it.
You measure all voltages, currents, and powers. How do use your "obvious
and elementary notions" to tell if the transmission line is conjugately
matched or not? How do you measure the impedance looking toward a typical
amateur radio transmitter without changing the very thing you are trying
to measure? Many have tried and many have failed.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

Cecil,

Are you suggesting that a steam engine is needed in addition to "obvious
and elementary notions"?

Let's see, how about a nice triple expansion engine fed from a Scotch
boiler fueled with the finest Welsh coal. Don't forget to raise steam
slowly, and make sure you don't tie down the safety valve.


8-)

73,
Gene
W4SZ

Cecil Moore wrote:
Reg Edwards wrote:

Indeed it is. R+jX one way and R-jX the other.

Why the vast amount of palaver and bickering about such an obvious and
elementary notion defeats the imagination.


Reg, you are in a room with a transmission line passing through it.
You measure all voltages, currents, and powers. How do use your "obvious
and elementary notions" to tell if the transmission line is conjugately
matched or not? How do you measure the impedance looking toward a typical
amateur radio transmitter without changing the very thing you are trying
to measure? Many have tried and many have failed.

On Tue, 2 Mar 2004 14:40:02 -0600, "John Smith"
wrote:
Check for reflected power in either direction.

Hi John,

You would be surprised how hard that is for some, especially when an
argument about the direction of current flow becomes part of the
turmoil.

If none, then it is conjugally matched exactly.

Still too simple, not enough gristle to chew on. ;-)

If it is about -14 dB down, that is good and close enough.

In three sentences you've said enough to resolve the matter. But not
enough to end the debate....

73's
Richard Clark, KB7QHC

Well sed!

Jack K9CUN