Hello Richard,

You asked for what it IS, several times, so you virtually left me no
choice.

Especially the first one (Zout = 9 ohms where the load is 16 Ohms,
RCout = -0.28) is very well documented as it was designed to have this
value. Without the extra measures, the value was below 9 Ohms. The
amplifier is time limited fully short circuit proof, so it was not
difficult to determine Zout at various loads. I put myself into
problems when publishing the documentation over here.

When we go back to my first posting in this thread (the first reply)
where I stated that amplifiers do not show 50 Ohms in general, is not
that strange and doesn't violate Walt's conclusions.

When I understand it well, Walt assumes tuning for maximum output at a
given drive (not necessarily the maximum drive). As mentioned earlier,
I support his findings.

When you don't touch the plate and load capacitor and change from 50
Ohms to a load with VSWR = 2, you violate Walt's conditions and the
amplifier will no long behave as a 50 Ohms source, hence what happens
with the 50W reflected power from JC's posting becomes more
complicated then just a transmission line problem.

Walt made a statement in this thread that an amplifier that obeys ZL =
Zout can have higher then 50% efficiency. I fully support this
statement also (Example Class C amplifier with narrow conduction angle
at the edge of current/voltage saturation, with efficiency over
75%). However, change the load and you get a complete other
situation. You have to retune to get back to Walt's condition.

From my experience, many devices with conventional amplifiers (like
the valve with pi-filter, or single transistor stages) are now being
replaced by other topologies where ZL Zout under specified load (as
these types of amplifiers are not optimized for maximum gain, but for
maximum power added efficiency). I think Tom, KT7ITM also have this
experience.

The example given by JC (huge reflection) and my own experience with
conventional and high efficiency topologies resulted in my statement
that a PA is not a 50 Ohms source. Maybe I had to be more precise to
mention the exceptions: forward power control loop as mentioned by
Roy, -tuning to maximum output after each change of load, -specially
designed negative feedback, -adding an attenuator. The reader can now
determine the category for his PA.

In case of doubt use the forward power measurement technique, when it
changes under varying load, your amplifier doesn’t behave as a 50 Ohms
source.

Best Regards,


Wim
PA3DJS
www.tetech.nl
without abc, PM will reach me

On Tue, 8 Jun 2010 12:17:37 -0700 (PDT), Wimpie
wrote:

When we go back to my first posting in this thread (the first reply)
where I stated that amplifiers do not show 50 Ohms in general, is not
that strange and doesn't violate Walt's conclusions.

Hi Wimpie,

Time to rewind:

On Thu, 27 May 2010 19:32:40 -0700 (PDT), walt wrote:

The source resistance data reported in Secs 19.8 and 19.9 were
obtained using the load variation method with resistive loads. Note
that of the six measurements of output source resistance reported in
Table 19.1, the average value of the resistance is 50.3 ohms obtained
with the reference load resistance of 51.2 ohms, exhibiting an error
of only 1.8 percent.

Considering these two explicit initial conditions and findings:

1. Using a Kenwood TS-830S transceiver as the RF source, the tuning
and loading of the pi-network are adjusted to deliver all the
available power into a 50 + j0-ohm load with the grid drive adjusted
to deliver the maximum of 100 watts at 4 MHz, thus establishing the
area of the RF power window at the input of the pi-network, resistance
RLP at the plate, and the slope of the load line. The output source
resistance of the amplifier in this condition will later be shown to
be 50 ohms. In this condition the DC plate voltage is 800 v and plate
current is 260 ma. DC input power is therefore 800 v ? 0.26 a = 208 w.
Readings on the Bird 43 wattmeter indicate 100 watts forward and zero
watts reflected. (100 watts is the maximum RF output power available
at this drive level.) From here on the grid drive is left undisturbed,
and the pi-network controls are left undisturbed until Step 10.

2. The amplifier is now powered down and the load resistance RL is
measured across the input terminals of the resonant pi-network tank
circuit (from plate to ground) with an HP-4815 Vector Impedance Meter.
The resistance is found to be approximately 1400 ohms. Because the
amplifier was adjusted to deliver the maximum available power of 100
watts prior to the resistance measurement, the averaged resistance RLP
looking into the plate (upstream from the network terminals) is also
approximately 1400 ohms. Accordingly, a non-reactive 1400-ohm resistor
is now connected across the input terminals of the pi-network tank
circuit and source resistance ROS is measured looking rearward into
the output terminals of the network. Resistance ROS was found to be 50
ohms.

Quite explicit. Rated power into the rated Z load revealed a
conjugate basis Z match (afterall 50=50) or an image basis Z match
(50=50). The pi-network simply transformed the source/load. Anyone
skilled with the concept of the Smith Chart can immediately follow
that logical construct.

We even get the plate resistance which conforms to within published
specifications for the pair of tubes.

We even get the near classic result of a conjugate basis Z match
efficiency (however, only in the first pass approximation).

How asking the same question:

"Does Walt's data support the evidence of a Conjugate Match?"

migrates into responses to other issues is a strange dance. I ask "up
or down," and everyone wants to vote sideways.

When you don't touch the plate and load capacitor and change from 50
Ohms to a load with VSWR = 2, you violate Walt's conditions

I have not the vaguest idea where you got the idea that I changed
anything. The totality of my discussion never budged from steps 1 and
2 and I deliberately and clearly confined all matters there and
repeated them more than occasionally.

In case of doubt use the forward power measurement technique,

I have, and the data I've asked from you was not intended for some
one-time design for a unique application. This is an Ham radio group,
and the object under consideration is an Ham transmitter. Feel free
to substitute freely among a similar class (frequency range, power
output) such that others might compare their own.

when it
changes under varying load, your amplifier doesn’t behave as a 50 Ohms
source.

This is the most curious statement that eventually comes down the
pike. It is like I am talking to a novice to explain:
"That is what the tuner is for!"

Maybe I had to be more precise to
mention the exceptions: forward power control loop as mentioned by
Roy,

What Roy is describing is nothing close to Walt's hypothesis that I
have confined to a single point observation. No one has advanced
claims made that demonstrate:
1. Constant Z across all loads;
2. Constant Z across all frequencies;
3. Constant Power across all loads;
4. Constant Power across all frequencies.
No competent Ham expects that of any Ham transmitter.

Walt reported a 50 Ohm source Z from a tube rig. I have measured a 50
Ohm Z from two of my own transistor rigs. The difference in
technology is not an issue. I have also been responsible for
measuring RF power and source/load specifications within the chain of
national standards laboratories. Stretching the term RF, this spanned
from DC to 12GHz for power levels up to 100W. The sources across the
board exhibited 50 Ohms Source Z.

Your own national lab is represented at:
http://www.vsl.nl/
They undoubtedly use the same reference citations as our National
Institutes for Science and Technology.

***********

Putting the entirety of this discussion aside, and returning to your
very special project with an 9 Ohm source of RF at 8 Mhz. How
efficient was its operation feeding a 50 Ohm line to a 50 Ohm load?
Can you document this with schematics, parts description, and measured
data at key points from drain through to the load? This was the level
of available resources that came with Walt's discussion.

73's
Richard Clark, KB7QHC

Richard Clark Inscribed thus:

How asking the same question:

"Does Walt's data support the evidence of a Conjugate Match?"

73's
Richard Clark, KB7QHC

Having struggled to keep up and understand the very different points of
view, indeed very confusing at times, I'm going to come down on the
side of "Yes, Walt's data does support evidence of a Conjugate Match."

--
Best Regards:
Baron.

On Wed, 09 Jun 2010 19:18:42 +0100, Baron
wrote:

Having struggled to keep up and understand the very different points of
view, indeed very confusing at times, I'm going to come down on the
side of "Yes, Walt's data does support evidence of a Conjugate Match."

Hi OM,

Thanks. Clear answers to clear questions are rare.

So:
2½ "Walt's data does support evidence of a Conjugate Match"
and
½ "Walt's data does not support evidence of a Conjugate Match"

As for confusion - the split vote must be proxy for the "silent
majority." Or, that majority cannot risk exposure. Shame? The only
issue is either with the data or the expression "Conjugate Match."
None seem anxious to avoid discussion of the expression - in fact that
conversation runs like a party line.

On the other hand, challenge the data? The numbers were cribbed? The
test gear was in the "off" position during a test? No. The data
seems to make sense. Competing data for the same initial conditions?
Hark! The scientific method rises from slumber with interest.

Nope, nada, negatory, no way, not going there.

Scientific method returns to its narcoleptic state.

73's
Richard Clark, KB7QHC

On Jun 9, 1:18*pm, Baron wrote:
Richard Clark Inscribed thus:
* "Does Walt's data support the evidence of a Conjugate Match?"

"Yes, Walt's data does support evidence of a Conjugate Match."

http://www.w2du.com/Appendix09.pdf

A purist might argue that, like a lossless transmission line, an ideal
conjugate match cannot exist in reality because of resistive losses
and non-linearities.

What might be a more accurate statement is: By definition, Walt's data
supports the evidence of a real-world Conjugate Match. Walt has
certainly defined in detail what he means by a "(real-world) Conjugate
Match".
--
73, Cecil, w5dxp.com

On 9 jun, 02:07, Richard Clark wrote:
On Tue, 8 Jun 2010 12:17:37 -0700 (PDT), Wimpie
wrote:

When we go back to my first posting in this thread (the first reply)
where I stated that amplifiers do not show 50 Ohms in general, is not
that strange and doesn't violate Walt's conclusions.

Hi Wimpie,

Time to rewind:

On Thu, 27 May 2010 19:32:40 -0700 (PDT), walt wrote:

The source resistance data reported in Secs 19.8 and 19.9 were
obtained using the load variation method with resistive loads. Note
that of the six measurements of output source resistance reported in
Table 19.1, the average value of the resistance is 50.3 ohms obtained
with the reference load resistance of 51.2 ohms, exhibiting an error
of only 1.8 percent.

Considering these two explicit initial conditions and findings:



1. Using a Kenwood TS-830S transceiver as the RF source, the tuning
and loading of the pi-network are adjusted to deliver all the
available power into a 50 + j0-ohm load with the grid drive adjusted
to deliver the maximum of 100 watts at 4 MHz, thus establishing the
area of the RF power window at the input of the pi-network, resistance
RLP at the plate, and the slope of the load line. The output source
resistance of the amplifier in this condition will later be shown to
be 50 ohms. In this condition the DC plate voltage is 800 v and plate
current is 260 ma. DC input power is therefore 800 v ? 0.26 a = 208 w.
Readings on the Bird 43 wattmeter indicate 100 watts forward and zero
watts reflected. (100 watts is the maximum RF output power available
at this drive level.) From here on the grid drive is left undisturbed,
and the pi-network controls are left undisturbed until Step 10.

2. The amplifier is now powered down and the load resistance RL is
measured across the input terminals of the resonant pi-network tank
circuit (from plate to ground) with an HP-4815 Vector Impedance Meter.
The resistance is found to be approximately 1400 ohms. Because the
amplifier was adjusted to deliver the maximum available power of 100
watts prior to the resistance measurement, the averaged resistance RLP
looking into the plate (upstream from the network terminals) is also
approximately 1400 ohms. Accordingly, a non-reactive 1400-ohm resistor
is now connected across the input terminals of the pi-network tank
circuit and source resistance ROS is measured looking rearward into
the output terminals of the network. Resistance ROS was found to be 50
ohms.

Quite explicit. *Rated power into the rated Z load revealed a
conjugate basis Z match (afterall 50=50) or an image basis Z match
(50=50). *The pi-network simply transformed the source/load. *Anyone
skilled with the concept of the Smith Chart can immediately follow
that logical construct.

We even get the plate resistance which conforms to within published
specifications for the pair of tubes.

We even get the near classic result of a conjugate basis Z match
efficiency (however, only in the first pass approximation).

How asking the same question:

* "Does Walt's data support the evidence of a Conjugate Match?"

migrates into responses to other issues is a strange dance. *I ask "up
or down," and everyone wants to vote sideways.

When you don't touch the plate and load capacitor and change from 50
Ohms to a load with VSWR = 2, you violate Walt's conditions

I have not the vaguest idea where you got the idea that I changed
anything. *The totality of my discussion never budged from steps 1 and
2 and I deliberately and clearly confined all matters there and
repeated them more than occasionally.

In case of doubt use the forward power measurement technique,

I have, and the data I've asked from you was not intended for some
one-time design for a unique application. *This is an Ham radio group,
and the object under consideration is an Ham transmitter. *Feel free
to substitute freely among a similar class (frequency range, power
output) such that others might compare their own. *

when it
changes under varying load, your amplifier doesn’t behave as a 50 Ohms
source.

This is the most curious statement that eventually comes down the
pike. *It is like I am talking to a novice to explain:
* * * * "That is what the tuner is for!"

Maybe I had to be more precise to
mention the exceptions: forward power control loop as mentioned by
Roy,

What Roy is describing is nothing close to Walt's hypothesis that I
have confined to a single point observation. *No one has advanced
claims made that demonstrate:
1. *Constant Z across all loads;
2. *Constant Z across all frequencies;
3. *Constant Power across all loads;
4. *Constant Power across all frequencies.
No competent Ham expects that of any Ham transmitter.

Walt reported a 50 Ohm source Z from a tube rig. *I have measured a 50
Ohm Z from two of my own transistor rigs. *The difference in
technology is not an issue. *I have also been responsible for
measuring RF power and source/load specifications within the chain of
national standards laboratories. *Stretching the term RF, this spanned
from DC to 12GHz for power levels up to 100W. *The sources across the
board exhibited 50 Ohms Source Z.

Your own national lab is represented at:http://www.vsl.nl/
They undoubtedly use the same reference citations as our National
Institutes for Science and Technology.

***********

Putting the entirety of this discussion aside, and returning to your
very special project with an 9 Ohm source of RF at 8 Mhz. *How
efficient was its operation feeding a 50 Ohm line to a 50 Ohm load?
Can you document this with schematics, parts description, and measured
data at key points from drain through to the load? *This was the level
of available resources that came with Walt's discussion.

73's
Richard Clark, KB7QHC

Hello Richard,

We can continue mentioning measurement results, do other claims, but
that may not converge. Your results show 50 Ohms output impedance,
mine show other. Such results cannot be verified easily, so this
remains food for endless discussions.

I decided to use another approach that can be verified by people
having a (spice) simulator. I did simulations for some circuits that
can be expected in the amateur world and aren't exotic. I put them
over he http://www.tetech.nl/divers/PA_impedance.pdf . Now people
can figure out what it IS and get their own educated opinion. I used
low frequencies to avoid discussion about the validity of the
simulations (parasitic inductances, etc).

From these simulations it is clear that small changes in load or drive
level result in large change of output impedance. This knowledge
resulted in my statement: "an RF PA isn't a 50 Ohms source", what was/
is heavily disputed by you.

Of course you can design to have better output VSWR under varying load
or drive, but this is generally not done for systems that just have to
deliver the power (transmitters).

If you want to reproduce some of the results yourself, we can compare
our spice netlists. I recently added a real class C example as this
was heavily discussed in another thread.

Best regards,


Wim
PA3DJS
www.tetech.nl
When you remove abc, PM will reach me.

On Jun 13, 5:08*pm, Wimpie wrote:
On 9 jun, 02:07, Richard Clark wrote:



On Tue, 8 Jun 2010 12:17:37 -0700 (PDT), Wimpie
wrote:

When we go back to my first posting in this thread (the first reply)
where I stated that amplifiers do not show 50 Ohms in general, is not
that strange and doesn't violate Walt's conclusions.

Hi Wimpie,

Time to rewind:

On Thu, 27 May 2010 19:32:40 -0700 (PDT), walt wrote:

The source resistance data reported in Secs 19.8 and 19.9 were
obtained using the load variation method with resistive loads. Note
that of the six measurements of output source resistance reported in
Table 19.1, the average value of the resistance is 50.3 ohms obtained
with the reference load resistance of 51.2 ohms, exhibiting an error
of only 1.8 percent.

Considering these two explicit initial conditions and findings:

1. Using a Kenwood TS-830S transceiver as the RF source, the tuning
and loading of the pi-network are adjusted to deliver all the
available power into a 50 + j0-ohm load with the grid drive adjusted
to deliver the maximum of 100 watts at 4 MHz, thus establishing the
area of the RF power window at the input of the pi-network, resistance
RLP at the plate, and the slope of the load line. The output source
resistance of the amplifier in this condition will later be shown to
be 50 ohms. In this condition the DC plate voltage is 800 v and plate
current is 260 ma. DC input power is therefore 800 v ? 0.26 a = 208 w.
Readings on the Bird 43 wattmeter indicate 100 watts forward and zero
watts reflected. (100 watts is the maximum RF output power available
at this drive level.) From here on the grid drive is left undisturbed,
and the pi-network controls are left undisturbed until Step 10.

2. The amplifier is now powered down and the load resistance RL is
measured across the input terminals of the resonant pi-network tank
circuit (from plate to ground) with an HP-4815 Vector Impedance Meter.
The resistance is found to be approximately 1400 ohms. Because the
amplifier was adjusted to deliver the maximum available power of 100
watts prior to the resistance measurement, the averaged resistance RLP
looking into the plate (upstream from the network terminals) is also
approximately 1400 ohms. Accordingly, a non-reactive 1400-ohm resistor
is now connected across the input terminals of the pi-network tank
circuit and source resistance ROS is measured looking rearward into
the output terminals of the network. Resistance ROS was found to be 50
ohms.

Quite explicit. *Rated power into the rated Z load revealed a
conjugate basis Z match (afterall 50=50) or an image basis Z match
(50=50). *The pi-network simply transformed the source/load. *Anyone
skilled with the concept of the Smith Chart can immediately follow
that logical construct.

We even get the plate resistance which conforms to within published
specifications for the pair of tubes.

We even get the near classic result of a conjugate basis Z match
efficiency (however, only in the first pass approximation).

How asking the same question:

* "Does Walt's data support the evidence of a Conjugate Match?"

migrates into responses to other issues is a strange dance. *I ask "up
or down," and everyone wants to vote sideways.

When you don't touch the plate and load capacitor and change from 50
Ohms to a load with VSWR = 2, you violate Walt's conditions

I have not the vaguest idea where you got the idea that I changed
anything. *The totality of my discussion never budged from steps 1 and
2 and I deliberately and clearly confined all matters there and
repeated them more than occasionally.

In case of doubt use the forward power measurement technique,

I have, and the data I've asked from you was not intended for some
one-time design for a unique application. *This is an Ham radio group,
and the object under consideration is an Ham transmitter. *Feel free
to substitute freely among a similar class (frequency range, power
output) such that others might compare their own. *

when it
changes under varying load, your amplifier doesn’t behave as a 50 Ohms
source.

This is the most curious statement that eventually comes down the
pike. *It is like I am talking to a novice to explain:
* * * * "That is what the tuner is for!"

Maybe I had to be more precise to
mention the exceptions: forward power control loop as mentioned by
Roy,

What Roy is describing is nothing close to Walt's hypothesis that I
have confined to a single point observation. *No one has advanced
claims made that demonstrate:
1. *Constant Z across all loads;
2. *Constant Z across all frequencies;
3. *Constant Power across all loads;
4. *Constant Power across all frequencies.
No competent Ham expects that of any Ham transmitter.

Walt reported a 50 Ohm source Z from a tube rig. *I have measured a 50
Ohm Z from two of my own transistor rigs. *The difference in
technology is not an issue. *I have also been responsible for
measuring RF power and source/load specifications within the chain of
national standards laboratories. *Stretching the term RF, this spanned
from DC to 12GHz for power levels up to 100W. *The sources across the
board exhibited 50 Ohms Source Z.

Your own national lab is represented at:http://www.vsl.nl/
They undoubtedly use the same reference citations as our National
Institutes for Science and Technology.

***********

Putting the entirety of this discussion aside, and returning to your
very special project with an 9 Ohm source of RF at 8 Mhz. *How
efficient was its operation feeding a 50 Ohm line to a 50 Ohm load?
Can you document this with schematics, parts description, and measured
data at key points from drain through to the load? *This was the level
of available resources that came with Walt's discussion.

73's
Richard Clark, KB7QHC

Hello Richard,

We can continue mentioning measurement results, do other claims, but
that may not converge. Your results show 50 Ohms output impedance,
mine show other. Such results cannot be verified easily, so this
remains food for endless discussions.

I decided to use another approach that can be verified by people
having a (spice) simulator. *I did simulations for some circuits that
can be expected in the amateur world and aren't exotic. *I put them
over he *http://www.tetech.nl/divers/PA_impedance.pdf. *Now people
can figure out what it IS and get their own educated opinion. I used
low frequencies to avoid discussion about the validity of the
simulations (parasitic inductances, etc).

From these simulations it is clear that small changes in load or drive
level result in large change of output impedance. *This knowledge
resulted in my statement: "an RF PA isn't a 50 Ohms source", what was/
is heavily disputed by you.

Of course you can design to have better output VSWR under varying load
or drive, but this is generally not done for systems that just have to
deliver the power (transmitters).

If you want to reproduce some of the results yourself, we can compare
our spice netlists. I recently added a real class C example as this
was heavily discussed in another thread.

Best regards,

Wim
PA3DJSwww.tetech.nl
When you remove abc, PM will reach me.

Hi Wim,

I quote a statement you made in your above post:

"From these simulations it is clear that small changes in load or
drive
level result in large change of output impedance. "

Now I agree that changing the drive level will result in a change in
output impedance. However, let's say you have just adjusted the amp to
deliver all the available power into a given load at a given drive
level, and now you change the load, but leave the drive level and all
other adjustments of the amp untouched. Are you saying this change in
load changes the output impedance? If so, please explain why.

In addition, which situation has the greatest priority, data obtained
from precise measurements or data obtained solely from simulations?

Walt, W2DU

On 13 jun, 23:43, walt wrote:
On Jun 13, 5:08*pm, Wimpie wrote:



On 9 jun, 02:07, Richard Clark wrote:

On Tue, 8 Jun 2010 12:17:37 -0700 (PDT), Wimpie
wrote:

When we go back to my first posting in this thread (the first reply)
where I stated that amplifiers do not show 50 Ohms in general, is not
that strange and doesn't violate Walt's conclusions.

Hi Wimpie,

Time to rewind:

On Thu, 27 May 2010 19:32:40 -0700 (PDT), walt wrote:

The source resistance data reported in Secs 19.8 and 19.9 were
obtained using the load variation method with resistive loads. Note
that of the six measurements of output source resistance reported in
Table 19.1, the average value of the resistance is 50.3 ohms obtained
with the reference load resistance of 51.2 ohms, exhibiting an error
of only 1.8 percent.

Considering these two explicit initial conditions and findings:

1. Using a Kenwood TS-830S transceiver as the RF source, the tuning
and loading of the pi-network are adjusted to deliver all the
available power into a 50 + j0-ohm load with the grid drive adjusted
to deliver the maximum of 100 watts at 4 MHz, thus establishing the
area of the RF power window at the input of the pi-network, resistance
RLP at the plate, and the slope of the load line. The output source
resistance of the amplifier in this condition will later be shown to
be 50 ohms. In this condition the DC plate voltage is 800 v and plate
current is 260 ma. DC input power is therefore 800 v ? 0.26 a = 208 w.
Readings on the Bird 43 wattmeter indicate 100 watts forward and zero
watts reflected. (100 watts is the maximum RF output power available
at this drive level.) From here on the grid drive is left undisturbed,
and the pi-network controls are left undisturbed until Step 10.

2. The amplifier is now powered down and the load resistance RL is
measured across the input terminals of the resonant pi-network tank
circuit (from plate to ground) with an HP-4815 Vector Impedance Meter.

On Sun, 13 Jun 2010 14:08:59 -0700 (PDT), Wimpie
wrote:

This knowledge
resulted in my statement: "an RF PA isn't a 50 Ohms source", what was/
is heavily disputed by you.

Hi Wim,

Your conclusion:
"Under maximum power output matching given certain drive (not
necessarily being the maximum drive), the output impedance equals the
load resistor (the so-called "conjugated match condition")."

It was not the only conclusion, but it certainly disputes what you say
above.

Given the easy access to real amplifiers available to Hams at their
own bench, and further given that they do not present any more
complexity than your own simulation; then I have to wonder why we have
wandered into strange topologies.

I am not interested in trying to follow 23 pages of dense presentation
where you could have simulated Walt's finals, validated or rejected
his data, and THEN formed your own conclusions. If this is a problem
of simulation (you don't have that tube handy) what about topology?

It looks more like a link coupled tank circuit from pre-WWII days. The
Tank Q looks to be non-existent. When I rummage through the paper I
find 4.4! This is certainly beyond the standard for PA design - and
we have swapped out of the tube into a mosfet (would you care to stick
to one objective?). Elsewhere (wandering back in tubes) I find a
value of 10.3 (elsewhere it is 11) which inhabits the lowest margin of
good design. Then an itinerant report of a cathode tank (????) whose
Q is 0.44. Q appears to be of little concern.

Again, typical Ham equipment shows Q as low as 10 - maybe, and that
would be for a dog; but those that I have seen typically fall around
15, sometimes 20. As the Z transformation in plate/drain circuits
varies by the square of Q, this is not inconsequential and it once
again has me wondering why the strange topology?

No, your paper lacks focus by trying to be all things (tubes, mosfets,
Class AB, Class C). You examine the most inconsequential details as
if they were equally important as those details that bear on your
concern. The paper lacks structure. Headings are nothing more than
feature descriptions, not argument development. There is a lot of
discussion of the idiosyncrasies of simulation - I am not interested
and that discussion creates the impression of hidden errors. Really,
this stuff goes into an appendix not as the object of the narrative.
The graphs are pretty diversions, but they don't add much. In the
software industry, this is spaghetti design.

I would prefer a conventional topology. I suppose that has come
through clear. Pick one significant point, re-edit this into 4 pages
and then you might have something interesting. This advice comes from
one of our American writers, Mark Twain:
"If I had more time, I would have written you a shorter letter."

73's
Richard Clark, KB7QHC

On 14 jun, 02:13, Richard Clark wrote:
On Sun, 13 Jun 2010 14:08:59 -0700 (PDT), Wimpie
wrote:

This knowledge
resulted in my statement: "an RF PA isn't a 50 Ohms source", what was/
is heavily disputed by you.

Hi Wim,

Your conclusion:
"Under maximum power output matching given certain drive (not
necessarily being the maximum drive), the output impedance equals the
load resistor (the so-called "conjugated match condition")."

It was not the only conclusion, but it certainly disputes what you say
above.

Given the easy access to real amplifiers available to Hams at their
own bench, and further given that they do not present any more
complexity than your own simulation; then I have to wonder why we have
wandered into strange topologies.

My findings are from practice before I had the opportunity to do PA
simulations.

I am not interested in trying to follow 23 pages of dense presentation
where you could have simulated Walt's finals, validated or rejected
his data, and THEN formed your own conclusions. *If this is a problem
of simulation (you don't have that tube handy) what about topology? *

23 pages is not that much as graphs and circuit diagrams dominate. If
you can provide me a circuit diagram I will figure out whether I can
simulate it or not.


It looks more like a link coupled tank circuit from pre-WWII days. The
Tank Q looks to be non-existent. *When I rummage through the paper I
find 4.4! *This is certainly beyond the standard for PA design - and
we have swapped out of the tube into a mosfet (would you care to stick
to one objective?). *Elsewhere (wandering back in tubes) I find a
value of 10.3 (elsewhere it is 11) which inhabits the lowest margin of
good design. *Then an itinerant report of a cathode tank (????) whose
Q is 0.44. *Q appears to be of little concern.

Fully agree with the low cathode Q, therefore it doesn't affect the
simulations results significantly.


Again, typical Ham equipment shows Q as low as 10 - maybe, and that
would be for a dog; but those that I have seen typically fall around
15, sometimes 20. *As the Z transformation in plate/drain circuits
varies by the square of Q, this is not inconsequential and it once
again has me wondering why the strange topology?

Tell me what Q I should use (evt, give me component values) in the
simulation, and I will change it for you.


No, your paper lacks focus by trying to be all things (tubes, mosfets,
Class AB, Class C). *

This is to support my statement that under real world amateur
conditions many PAs do not obey ZL = Zout*. If I have some time I will
add a push-pull transfomer coupled amplifier also.

You examine the most inconsequential details as
if they were equally important as those details that bear on your
concern. *The paper lacks structure. *Headings are nothing more than
feature descriptions, not argument development. *There is a lot of
discussion of the idiosyncrasies of simulation - I am not interested
and that discussion creates the impression of hidden errors. *Really,
this stuff goes into an appendix not as the object of the narrative.
The graphs are pretty diversions, but they don't add much. *In the
software industry, this is spaghetti design.

I would prefer a conventional topology. *I suppose that has come
through clear. *Pick one significant point, re-edit this into 4 pages
and then you might have something interesting. *This advice comes from
one of our American writers, Mark Twain:
* * * * "If I had more time, I would have written you a shorter letter."

73's
Richard Clark, KB7QHC

simulation is general practice in the design flow, I know it has
limitations. Of course I could use ADS, but most people don't have
that at home, so I decided to use spice as this is used by many.

If you believe I am so wrong, why don't you present some simulations
to show that my original statement is completely wrong?

Best regards,


Wim
PA3DJS
www.tetech.nl
without abc, PM will reach me.