Dave wrote:
have you guys read this one yet?

www.qsl.net/w9dmk/MPTT.pdf

Yes, as a matter of fact, I have. It tends to support my argument
with Jeff Anderson, wa6ahl, on this newsgroup from about a decade
ago, but is much more thorough and eloquent than I ever could be.
--
73, Cecil http://www.qsl.net/w5dxp



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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.

73,
Gene
W4SZ

Cecil Moore wrote:
Dave wrote:

have you guys read this one yet?

www.qsl.net/w9dmk/MPTT.pdf


Yes, as a matter of fact, I have. It tends to support my argument
with Jeff Anderson, wa6ahl, on this newsgroup from about a decade
ago, but is much more thorough and eloquent than I ever could be.

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

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]

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

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

"Lossless resistance?" Would that be zero resistance,
or perhaps a negative resistance, as in the active part of
a tunnel diode's V-I characteristic?

I am a career EE, with a couple of graduate EE degrees;
and this is something entirely new to me. Could you explain
this concept, and/or provide some references?

Thanks, Ed

On Wed, 03 Mar 2004 00:56:57 GMT, "Old Ed"
wrote:

"Lossless resistance?" Would that be zero resistance,
or perhaps a negative resistance, as in the active part of
a tunnel diode's V-I characteristic?

I am a career EE, with a couple of graduate EE degrees;
and this is something entirely new to me. Could you explain
this concept, and/or provide some references?

Thanks, Ed

Hi Ed,

This is the most useless term employed in these threads; what I call a
difference without a distinction.

To put it shortly, it is the resistance observed in an infinite
transmission line (better known as the Characteristic Z) or the
resistance of an antenna (better known as the Radiation Resistance).
You will note that a competent engineer already understands the nature
of this resistance, shrubs may need more words to obtain the same
knowledge.

Some explanations like to force it into the same definition of Z, and
then add more words to denote there is not reactance, and then more
words to add there is no heat generated.

In other words (too many of them) the issue is driven from the physics
of heat which if anyone peeled back the onion layers, then they would
find they have not actually escaped from it all, and more words are
forced into the definition to argue what dissipation means.

Principally, a new instrument has been added to the Ohm Meter, the
thermometer, to prove you have in fact measured the value of a carbon
composition resistor. No one actually does this; no one actually
could offer a suitable caloric answer if their life depended on it;
and certainly no one could tell you what the resistance is from a
thermometer reading. But they would demand it is necessary none the
less. ;-)

73's
Richard Clark, KB7QHC

Old Ed wrote:
"Couild you explain this concept, and/or provide some references?"

Suppose we adjust a variable d-c supply to full-scale indication on an
external meter. Next, install a chopper (lossless on-off circuit) driven
at a high frequency to produce a square wave interruption of the d-c
with a 50% duty cycle, and insert the chopper contacts in series with
the external meter.

The chopper connects the external meter 50% of the time and disconnercts
it 50% of the time. The meter reads 50% of full scale.

Another way to reduce the scale reading to 50% is to insert a resistor
in series with the meter. If it is an 0-1 ma meter and if it has an
internal resistance of 1000 ohms, insertion of a 1000-ohm resistor in
series with the meter will reduce the meter scale indication to 50%.

The chopper as part of the meter source eliminates current to the meter
50% of the time.

The resistor which has the same effect and produces the same scale
indication as the chopper on the effective output current exacts its
loss of 0.0005 amp x 0.5 volt or 0.25 milliwatt during 100% of the time.

The chopper eliminates the power-losing resistor by substituting
off-time in the power source. The source only supplies the power used by
the load. With a resistor limiting power to the load, the source
supplies its loss and the load power.

The power in the load, a meter in our example, is the same using either
the resistor or the chopper. The resistor is analogous to a Class-A
amplifier. The chopper is analogous to a Class-C amplifier.

The off-time has the same effective opposition to current to a load as a
dissipative resistance. As the time-limited currented opposition to load
current consumes no power, it is called a dissipationless resistance.

Best regards, Richard Harrison, KB5WZI

It is in the same class of parts with inductancless inductors,
and capacitanceless capacitors are in.
With lossless resistance they can form
a lossless, non-energy storing, extremely low/high Q, network.
No need for tuning either!
(sorry-just not serious today)




"Old Ed" wrote in message
hlink.net...
"Lossless resistance?" Would that be zero resistance,
or perhaps a negative resistance, as in the active part of
a tunnel diode's V-I characteristic?

I am a career EE, with a couple of graduate EE degrees;
and this is something entirely new to me. Could you explain
this concept, and/or provide some references?

Thanks, Ed