Richard Clark wrote:

On Mon, 28 Feb 2005 22:53:17 GMT, gwhite wrote:

Obviously people don't have 100 W (or more!) network analyzers looking into the
output and pretending the device is similar to a linear small signal device.

Hi OM,

Well, it is more accurate to say that you don't, that is for sure.
Defining a solution by negative results can fill up a library without
any positive accomplishment. Obviously people don't have a nuclear
reactor, or lunar lander, or bank account to balance the national
debt. The joke of this, of course, is that no one needs a 100 W (or
more!) network analyzer, or nuclear reactor, or lunar lander, or bank
account to balance the national debt to explain a rather more trivial
problem. Which, by the way, has nothing to do with pretending at all.

You entirely missed the point. You don't know the output impedance because you
don't have a way of determining it by swinging the output full-scale. Even for
class A, large signals will/can have rail to rail swing. The device will not be
linear for large swings: sinusoidal input swing will not result in a sinusoidal
output swing. But "impedance" is a sinusoidal (s-domain) concept. So how can
you define an impedance--a sinusoidal concept--when the waveform is not
sinusoidal for an inputted sine wave? The point is that the output impedance is
time dependent ("causes" the non-sinusoid output for sinusoid drive), which
rather makes the concept questionable. As I wrote earlier, one might decide to
consider a time averaged impedance, but I'm not clear on what the utility would
be.

The suggestion that
requires load pull test equipment and that can be expensive
does not negate its existence which commonly proves what you choose to
dismiss as impossible. I have calibrated this gear (called an
artificial or active load), and the gear (called transmitters) it
tests and there are no differences in Physics based upon your
presumption of low-power/high-power demarcations.

There is no "presumption." Linear parameters and theorems totally ignore
practical limitations--this is a fact and you can look it up in just about any
text on circuit analysis. The simple linear model is perfectly okay for small
signal devices. It isn't okay for large signal devices. In any case, load pull
equipment does not make the pretense of defining output impedance of an active
large signal device. It does say what the load needs to be to acquire maximum
power out of the device.

To say
pretending the device is similar to a linear small signal device
is one of those assumptions forced into the argument.

No, it isn't. Thevenins and conjugate matching (for maximum power transfer) are
explicitly linear small signal device models. Their use in RF PA output design
is a misapplication.

There are any
number of ways to do something wrong.

We're talking about one of them. Misapplying small signal linear parameters to
the output of a large signal device.

Trumping none of these straw
men validates another wrong impression passing as theory.

This
returns us to the imposition of impossibilities to answer a rather
mundane concept, eg.
pretending the device is similar to a small nuclear device
pretending the device is similar to a mars rover
pretending the device is similar to the national debt of Lithuania

Who are you quoting and why?

So to return to a common question that seems to defy 2 out of 3
analysis (and many demurred along the way) - A simple test of a
practical situation with a practical Amateur grade transistor model
100W transmitter commonly available for more than 20-30 years now:
1. Presuming CW mode into a "matched load" (any definition will do);

Any definition won't do, and for this discussion the specific "won't do" is
using conjugate matching which is a small signal (linear) model.

2. Report the DC power consumed before hitting the key;
3. Report the DC power consumed while holding the key.

Hey, at least you're recognizing that DC power is important. Where in conjugate
matching ideas or Thevenins theorem do you see any concern of DC power? That's
right, you don't because they a simple small signal models where DC power and
voltage have no bearing because the signals are so small, relatively speaking.

Concurrently note:
A. Report Heat Sink Temperature for a previously idle/rcv condition;
B. Report Heat Sink Temperature after 10 minute key-down.

For a hypothetical "100W" model (again, a contemporary, common example
for Amateur use) available through standard commercial venues:
2. About 20W - 30W
3. About 200W - 250W
A. About 20 degrees C (or room temperature)
B. Well above 37 degrees C (or skin temperature)

Now, if we are to be any judge of efficiency (Thevenin does not have
to be invoked, condemned, or venerated); then it runs close to 50%
(±10%). Others can invoke their favorite deity to explain.

*You* brought up Thevenins and armchair philosophy regarding it, not me. I said
Thevenins was irrelevent, and now you appear to agree with me. Ken effectively
brought up conjugate matching, not me. The original comment I was challenging
was:

"...the antenna works as an impedance mathcing network that matches the output
stages impedance to the radiation resistance."

I simply wanted to make it clear that the "matching" done was not an issue of
"output impedance" per se. It is an issue of how the transistor is to be loaded
to extract maximum ouput power.

Now, if we are to be any judge of dissipation (no requirement for
advanced degree); then heat as a loss by virtue of less than 100%
efficiency is quite evident. Others can invoke photons to describe
why.

To forestall any armchair engineers, yes, this efficiency is System
efficiency. However, I would be surprised if a practical common
Amateur grade transistor model transmitter commonly available for more
than 20-30 years now has any configuration that does not apply supply
voltage directly to the final transistors; and instead adds a
significant current path outside of this load (citations to available
schematics would be compelling, but any argument without this would be
speculation). It takes very little effort to subtract out the power
drain of the receive mode (being very representative of the similar
power demand of supporting circuitry for transmit up to the driver
stage). Barring such amazing evidence of a significant power drain
not found in the finals, it follows that a simple computation of
efficiency has its merit and has been met.

Exactly. It is about DC to RF efficiency, as I've been pointing out since my
first post, and which you initially commented was "nonsense" but now seem to
agree with. "Impedance matching" meant in the normal sense of conjugate
matching for maximum transfer of power is a misapplied small signal
concept/model. I think that is all I've really been saying.

On Tue, 01 Mar 2005 18:06:18 GMT, gwhite wrote:

It is about DC to RF efficiency,

Put a number to it.

as I've been pointing out since my
first post, and which you initially commented was "nonsense"

Hi OM,

And so it remains with additional elaborations not quoted here.

but now seem to agree with.

Seeming is a rather insubstantial thing to hang your theories on.

"Impedance matching" meant in the normal sense of conjugate
matching for maximum transfer of power

And this reveals the error of "Seeming" because the so-called meaning
you ascribe is this same nonsense. Pay more attention to reading
instead of writing. It has been pointed out more than once, and by
several, that Matching comes under many headings. The most frequent
violation is the mixing of concepts and specifications (your text is
littered with such clashes).

is a misapplied small signal
concept/model. I think that is all I've really been saying.

And I preserved this clash quoted above as an example. If there is
any misapplication, you brought it to the table with this forced
presumption. The misapplication of S parameters to a large signal
amplifier is one thing, to project this error backwards into the
fictive theory that there is some difference between large and small
signal BEHAVIOR (not modeling) is tailoring the argument to suit a
poorly framed thesis.

None of your dissertation reveals any practical substantiation, hence
it falls into the realm of armchair theory. We get plenty of that
embroidered with photonic wave theory that is far more amusing.

73's
Richard Clark, KB7QHC

Richard Clark wrote:

On Tue, 01 Mar 2005 18:06:18 GMT, gwhite wrote:

It is about DC to RF efficiency,

Put a number to it.

as I've been pointing out since my
first post, and which you initially commented was "nonsense"

Hi OM,

And so it remains with additional elaborations not quoted here.

but now seem to agree with.

Seeming is a rather insubstantial thing to hang your theories on.

Well they are apparently your's too! Your own example of testing your own PA
said absolutely zip about output-Z. The most you could say is how the circuit
is loaded and its RF/DC efficiency. You're agreeing with me and can't even seem
to recognize it.

"Impedance matching" meant in the normal sense of conjugate
matching for maximum transfer of power

And this reveals the error of "Seeming" because the so-called meaning
you ascribe is this same nonsense.

Here's the original quote [Ken]:

"When the correct matching is done, the antenna works as an impedance mathcing
network that matches the output stages impedance to the radiation resistance."

He brought up "matching to the output impedance" (of the device), not me. There
is no "misinterpretation of meaning" when it comes to making statements about
matching output impedance to a load impedance. The meaning is well-understood
and precise. It means conjugate matching for maximum power transfer, and this
is explicitly sourced from small signal theory. Small signal theory is
oblivious to practical factors like supply rails and efficiency. These
practical factors are paramount in PA design. Thus to apply a theory that
ignores paramount factors is to beg a design which will likely be non-optimal.

Pay more attention to reading
instead of writing.

I'm paying attention, you agree with me but don't have the background to
understand it.

It has been pointed out more than once, and by
several, that Matching comes under many headings. The most frequent
violation is the mixing of concepts and specifications (your text is
littered with such clashes).

No, you still don't get it. I don't have a problem with saying it is
"matched." For example, I said a PA needs to be "load-line matched." This has
a specific meaning, and that meaning explicitly isn't "impedanced matched,"
which means something else. If you don't bother to know what the words mean, I
might as well speak Swahili.

is a misapplied small signal
concept/model. I think that is all I've really been saying.

And I preserved this clash quoted above as an example. If there is
any misapplication, you brought it to the table with this forced
presumption.

There is no forced presumption. The words have explicit definitions. If you
don't know the language, you have no way of communicating.

The misapplication of S parameters to a large signal
amplifier is one thing, to project this error backwards into the
fictive theory that there is some difference between large and small
signal BEHAVIOR (not modeling) is tailoring the argument to suit a
poorly framed thesis.

The models come from behavior and/or device physics, and were developed for the
express purpose of efficient design methodology. Small signal models can (and
do) conveniently ignore large signal concerns such as efficiency and supply
rails, because such concerns are irrelevent in the small signal milieu. To
apply a model to a milieu for which the model is not suited begs a non-optimal
design. The output-impedance concept itself is quite dubious for large signal
amplifiers.

None of your dissertation reveals any practical substantiation, hence
it falls into the realm of armchair theory. We get plenty of that
embroidered with photonic wave theory that is far more amusing.

You are off track.

I read in sci.electronics.design that gwhite wrote
(in ) about '1/4 vs 1/2 wavelength
antenna', on Wed, 2 Mar 2005:

I might as well speak Swahili.


Good idea! Furahini mkaimbe. The wrangling is getting tiresome.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

On Wed, 02 Mar 2005 19:06:32 GMT, gwhite wrote:
but now seem to agree with.
Seeming is a rather insubstantial thing to hang your theories on.
Well they are apparently your's too!

Hi OM,

From seeming to appearances - leaps of faith are better suited for
debate at the Vatican.

The remainder, unquoted due to repetition of the same basic errors,
has already been commented upon in another posting. Oh, except the
more entertaining jousts:
Pay more attention to reading instead of writing.
I'm paying attention, you agree with me but don't have the background to
understand it.

Mmm-hmm :-)

To be so eagerly embraced as a fellow fool! Something of the chess
equivalent of the sacrificial queen gambit.

73's
Richard Clark, KB7QHC

In article , gwhite wrote:
[...]
Here's the original quote [Ken]:

"When the correct matching is done, the antenna works as an impedance mathcing
network that matches the output stages impedance to the radiation resistance."

Yes, I stand by and have just in another part of the thread once again
explained that indeed the impedance is matched. ie: If you make a small
change in the impedance in any direction the power decreases. Increasing
the resistance is the obvious one. The other three are because the
protection circuits act. The OP had a completed transmitter he was
connecting to a length of wire.



--
--
forging knowledge

Ken Smith wrote:

In article , gwhite wrote:
[...]
Here's the original quote [Ken]:

"When the correct matching is done, the antenna works as an impedance mathcing
network that matches the output stages impedance to the radiation resistance."

Yes, I stand by and have just in another part of the thread once again
explained that indeed the impedance is matched. ie: If you make a small
change in the impedance in any direction the power decreases.

Driven to max swing, this is true. But it is because of asymmetrical clipping,
not because of conjugate mismatch. For lower drives, what you say won't
necessarily be true *unless* you've mis-designed according to conjugate match
ideals. Your argument is circular.

If you design for conjugate match, you're right. I'm saying: don't do that. If
I design for load line match and you design for conjugate max (both pf us using
the same device and supply), I will get a higher peak power than you will.
However, you'll get to be right about how your amp acts regarding diverging from
conjugate load. But it is irrelevent: you made a fundamental mistake.

Increasing
the resistance is the obvious one. The other three are because the
protection circuits act. The OP had a completed transmitter he was
connecting to a length of wire.

In article , gwhite wrote:
[...]
You entirely missed the point. You don't know the output impedance because you
don't have a way of determining it by swinging the output full-scale.

You don't have to swing the output full-scale to measure the impedance.
Any change in the load, no matter how small, will cause a change in the
output voltage and the output current. From these you can calculate the
output impedance at the current operating point.

When a transistor is operating under large signal conditions into a tuned
load, there is still an output impedance and this impedance still
discribes what will happen for small changes in the load.


--
--
forging knowledge

I read in sci.electronics.design that Ken Smith
wrote (in )
about '1/4 vs 1/2 wavelength antenna', on Wed, 2 Mar 2005:
In article , gwhite wrote:
[...]
You entirely missed the point. You don't know the output impedance because you
don't have a way of determining it by swinging the output full-scale.

You don't have to swing the output full-scale to measure the impedance.
Any change in the load, no matter how small, will cause a change in the
output voltage and the output current. From these you can calculate the
output impedance at the current operating point.

When a transistor is operating under large signal conditions into a tuned
load, there is still an output impedance and this impedance still
discribes what will happen for small changes in the load.


This incremental impedance is one of several different impedances that
can be defined for a non-linear source. No one is more valid
conceptually than another, but some are of more practical significance
than others.

The point is that if you want to talk/write about one of these
impedances, you need, to prevent misunderstanding, use a precise term,
such as 'incremental output source impedance' and define it.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

In article ,
John Woodgate wrote:
[...]
The point is that if you want to talk/write about one of these
impedances, you need, to prevent misunderstanding, use a precise term,
such as 'incremental output source impedance' and define it.

You are right. I really needed to be more clear in the first posting I
did. That bridge has now been crossed and this is getting tiresome. If
the OP doesn't come in with more questions, I'm out of here.

--
--
forging knowledge