Transmitter Output Impedance
 

On 5/19/2011 2:26 PM, K7ITM wrote:
On May 19, 11:25 am, Cecil wrote:
On May 19, 9:03 am, wrote:

From simulation, but now a pi filter C=6pF, L=72u, C=6pF, load = 2570
Ohms

You just proved one of my points. Inventing impedors that do not exist
in reality in order to rationalize the real-world delay through a real-
world loading coil is exactly what I have been complaining about. Are
the imaginary lumped-circuit capacitors, to which you are forced to
resort, part of the actual impedance in reality or a figment of your
imagination?

http://hamwaves.com/antennas/inductance/corum.pdf
"The concept of coil 'self-capacitance' is an attempt to circumvent
transmission line effects on small coils when the current distribution
begins to depart from its DC behavior." About the capacitors you added
above it says: "Of course, this is merely a statistical determination
appropriate for computations ... and *not at all a physical
quantity*."

The reason that the source voltage and source current are in phase in
the example is because the load resistor equals the Z0 of the coil
which is functioning in transmission line mode with a VF = 0.019, i.e.
like a transmission line, it is indeed 0.1167 wavelengths long
electrically. I have verified such (within a certain degree of
accuracy) through bench experiments.
--
73, Cecil, w5dxp.com

First I'll point out that the model Wim used doesn't match "the
concept of coil self-capacitance," so it's not clear that the rest of
what you wrote is relevant.

Now, what do you do about your coils when you discover that they do
NOT behave like a TEM transmission line? Indeed they do not; it's
pretty easy to verify from measurements on real coils and real
circuits. It seems like now you are stuck, because you (seem to) have
a lot of trouble looking at a circuit and understanding what's really
important and what isn't, with regard to performance in a particular
application. Sometimes it's appropriate to use a model that goes well
beyond a simple transmission line model of a coil; sometimes the
simple transmission line model is far more complex than you need. See
Wim's previous posting about the value of understanding that.

FWIW, I understand perfectly well where the capacitances Wim put into
his model come from. I know exactly how I would estimate them from a
particular physical configuration, and I suppose Wim does something
very similar to what I would. They come very much from the real
physical world, not from our imaginations.

Cheers,
Tom

And, I find the lack of stray capacitance in Cecil's model much harder
to believe than the presence of them in Wim's model.

John

Transmitter Output Impedance
 

On 5/19/2011 1:53 PM, Cecil Moore wrote:
On May 19, 12:53 pm, John wrote:
In that case I have no need of S11 or reflections or light. I only need
to know that the Smith chart tells me that a 200 ohm load looks like a
50 ohm load through a 1/4WL-100 ohm line.

Well there you go - my point exactly - it "looks like" but appearances
can be deceiving. You and I know that they are not identical because
we are smarter than the average bear and the IEEE has different
definitions for those two radically different kinds of impedances. We
know that it is a virtual image of 50 ohms because no 50 ohm resistor
exists in reality and no zero reflection coefficient exists in
reality. In mathematical terms, there is no one to one correspondence
between a 50 ohm dummy load and a 50 ohm antenna.
--
73, Cecil, w5dxp.com

Well, Cecil, we've now reached the end. No resistor exists in reality so
no transmitters, waves, light, transmission lines exists in reality.
There is no one to one correspondence between you and sanity.

This is just plain stupid. You only want to argue.

John

Transmitter Output Impedance
 

On 19 mayo, 20:25, Cecil Moore wrote:
On May 19, 9:03*am, Wimpie wrote:

From simulation, but now a pi filter C=6pF, L=72u, C=6pF, load = 2570
Ohms

You just proved one of my points. Inventing impedors that do not exist
in reality in order to rationalize the real-world delay through a real-
world loading coil is exactly what I have been complaining about. Are
the imaginary lumped-circuit capacitors, to which you are forced to
resort, part of the actual impedance in reality or a figment of your
imagination?

http://hamwaves.com/antennas/inductance/corum.pdf
"The concept of coil 'self-capacitance' is an attempt to circumvent
transmission line effects on small coils when the current distribution
begins to depart from its DC behavior." About the capacitors you added
above it says: "Of course, this is merely a statistical determination
appropriate for computations ... and *not at all a physical
quantity*."

The reason that the source voltage and source current are in phase in
the example is because the load resistor equals the Z0 of the coil
which is functioning in transmission line mode with a VF = 0.019, i.e.
like a transmission line, it is indeed 0.1167 wavelengths long
electrically. I have verified such (within a certain degree of
accuracy) through bench experiments.
--
73, Cecil, w5dxp.com

Cecil,

Lumped circuit approach gives a good solution for your brainteaser
(maybe against your expectations or hope). It is just distributed
capacitance to ground that can be concentrated into 1 or more
capacitors if you are well below the first resonance frequency.

In a real application when using a lumped 72uH inductor for
calculations, one will find out that the capacitors for a certain
application (for example pi-filter section) have to be somewhat
smaller then based on the lumped circuit calculation.

Regarding transmission line behavior
It is the reason to mention "without using transmission line
sections". Because my PSPICE package also allows use of transmission
lines, if convenient I use them. Do you know how I made my first guess
for the capacitors? Just by using transmission line theory. BTW,
what is the wire length of the inductor in your HF rig (for 4 MHz
band)? It is very likely well below the length for the bugcatcher
example.

Did you know that many delay lines were/are made by using multiple CLC
sections (for example used in oscilloscopes)?

Again, look to the circuits of your rig, do you really think that the
design is carried out by modelling each component as a transmission
line. The answer is no (for sure).

We have various religions around the globe; I think we don't need
another one based on transmission lines! Maybe for you it was
wonderful to explore transmission line theory, but for RF Engineers/
Designers (antenna designers included), it is just one of their means
to get the job done.

Wim
PA3DJS
www.tetech.nl

Transmitter Output Impedance
 

On May 19, 3:21*pm, John KD5YI wrote:
This is just plain stupid.

I agree. Your above posting is just plain stupid. You are stating the
opposite of what I have said hoping some readers will not notice.
Resistors exist *in reality* e.g. in dummy loads. You are promoting E/
I ratios, existing as virtual resistances, to be as real as a physical
resistor. Hopefully, no one ever loads his virtual gun with one of
those virtual resistances and fires it at you. Question is, would you
die or not? It has been said that everyone creates his own reality and
it must be true. You guys have created models of reality in your minds
that bear very little resemblance to the real world.

In the field of optics, an real image that actually exists in reality
is clearly differentiated from a virtual image which is an illusion
that doesn't actually exist where it appears to exist. Light waves are
EM waves. RF waves are EM waves. You guys are promoting a model that
considers virtual images to actually exist at the point where they
appear to exist but are only an illusion. I agree with you - that is
just plain stupid.

To summarize: Resistors, capacitors, and inductors, defined under the
concept of impedors (from "The IEEE Dictionary") are real-world
devices with a physical existence - one can pick them up and touch
them.

E/I ratios, containing resistance plus capacitive or inductive
reactance, are impedances that do not have a physical existence. Their
existence is conceptual and exists only in human minds capable of
concepts (much like the concept of God).

When you are standing four feet from a mirror and your image appears
four feet behind the mirror, you are arguing that you can replace your
actual self with an alternate self four feet behind the mirror and
everything will be exactly the same. I agree with you - that is just
plain stupid.
--
73, Cecil, w5dxp.com

Transmitter Output Impedance
 

On May 19, 3:27*pm, Wimpie wrote:
We have various religions around the globe; I think we don't need
another one based on transmission lines!

Actually, what I am attempting to do is discourage your lumped-circuit
religion, where a 100 uH, 10" long coil, can propagate an RF signal in
3 ns, and move you guys closer to the reality of Maxwell's equations.
--
73, Cecil, w5dxp.com

Transmitter Output Impedance
 

On 19 mayo, 23:15, Cecil Moore wrote:
On May 19, 3:21*pm, John KD5YI wrote:

This is just plain stupid.

I agree. Your above posting is just plain stupid. You are stating the
opposite of what I have said hoping some readers will not notice.
Resistors exist *in reality* e.g. in dummy loads. You are promoting E/
I ratios, existing as virtual resistances, to be as real as a physical
resistor. Hopefully, no one ever loads his virtual gun with one of
those virtual resistances and fires it at you. Question is, would you
die or not? It has been said that everyone creates his own reality and
it must be true. You guys have created models of reality in your minds
that bear very little resemblance to the real world.

In the field of optics, an real image that actually exists in reality
is clearly differentiated from a virtual image which is an illusion
that doesn't actually exist where it appears to exist. Light waves are
EM waves. RF waves are EM waves. You guys are promoting a model that
considers virtual images to actually exist at the point where they
appear to exist but are only an illusion. I agree with you - that is
just plain stupid.

To summarize: Resistors, capacitors, and inductors, defined under the
concept of impedors (from "The IEEE Dictionary") are real-world
devices with a physical existence - one can pick them up and touch
them.

E/I ratios, containing resistance plus capacitive or inductive
reactance, are impedances that do not have a physical existence. Their
existence is conceptual and exists only in human minds capable of
concepts (much like the concept of God).

When you are standing four feet from a mirror and your image appears
four feet behind the mirror, you are arguing that you can replace your
actual self with an alternate self four feet behind the mirror and
everything will be exactly the same. I agree with you - that is just
plain stupid.
--
73, Cecil, w5dxp.com

Cecil,

I already expected that you wouldn't solve my brainteaser (so I did it
in advance), Here is the result for the 100V, 4 MHz sinusoidal source
in series with 796pF, load pulling with 51.2 Ohms and 44.6 Ohms:

V_out (51.2 Ohms) = 71.5V, I_out = 1.396A
V_out (44.6 Ohms) = 66.5V, I_out = 1.491A

Delta_V = 5.0V, Delta_I = 0.095A,

Hence Rout = 52.6 Ohms.

Power into 50 Ohms = 50W.

¡Really strange!, that a fully imaginary output impedance of -j50 Ohms
results in real 52.6 Ohms output impedance based on the scalar load
pulling referenced by you.

I also applied complex load pulling (that is taking phase change into
account) and Tom's off-carrier injection method to the same source.
Both methods put out Zout = -j50 Ohms (yes, the correct value).

You are criticizing Tom's method without any solid foundation, but you
referenced to a method with very limited application as shown in this
simple example.

You are mixing coherent signal theory with non-coherent signal theory
(narrow band RF versus unspecified optical), also your reply above has
no relevance to PA's for HF amateur service.

Cecil, we have all our specialities and limitations. It is becoming
clear that you lack experience in the field of signal processing and
RF (systems) Engineering. This is no problem, because many people can
live without it. Instead of continuing the way you do, you can better
try to grab some of the concepts offered by others. I am sure it will
give you better insight in what happens in RF systems, in considerably
less time.


Wim
PA3DJS
www.tetech.nl

Transmitter Output Impedance
 

On 19 mayo, 23:23, Cecil Moore wrote:
On May 19, 3:27*pm, Wimpie wrote:

We have various religions around the globe; I think we don't need
another one based on transmission lines!

Actually, what I am attempting to do is discourage your lumped-circuit
religion, where a 100 uH, 10" long coil, can propagate an RF signal in
3 ns, and move you guys closer to the reality of Maxwell's equations.
--
73, Cecil, w5dxp.com

Hello Cecil,

I am not addicted to "lumped circuits", I just use the appropriate
model. Many amateurs built and / or designed their own HF PA (and
other circuitry relevant to the hobby). Do you really think that they
all considered every component to be a transmission line?

Transmission lines in general.
I agree with Tom, "Transmission line approach" is also just a model
with limited validity. It all depends on the Engineer/Designer whether
to use it or misuse it.


Wim
PA3DJS
www.tetech.nl

Transmitter Output Impedance
 

On 5/19/2011 12:27 AM, K7ITM wrote:


By the way, have you seen this:

http://www.vk1od.net/transmissionline/W5DXPEA.htm

?

Transmitter Output Impedance
 

On May 19, 4:08*pm, John KD5YI wrote:
On 5/19/2011 12:27 AM, K7ITM wrote:

By the way, have you seen this:

http://www.vk1od.net/transmissionline/W5DXPEA.htm

?

I hadn't seen that particular one, John. While looking at it, though,
I clipped off the last of the URL to get to Owen's transmission lines
page. Lots of recommended reading there. I've always found Owen's
musings to be well thought out and thought-provoking.

Cheers,
Tom

Transmitter Output Impedance
 

On 5/19/2011 10:30 PM, K7ITM wrote:
On May 19, 4:08 pm, John wrote:
On 5/19/2011 12:27 AM, K7ITM wrote:

By the way, have you seen this:

http://www.vk1od.net/transmissionline/W5DXPEA.htm

?

I hadn't seen that particular one, John. While looking at it, though,
I clipped off the last of the URL to get to Owen's transmission lines
page. Lots of recommended reading there. I've always found Owen's
musings to be well thought out and thought-provoking.

Cheers,
Tom

I agree wholeheartedly, Tom. He used to be present here and I followed
his posts with enthusiasm. Alas, he has not posted in some time now.

I emailed him and inquired as to his well-being tonight. I hope he can
rejoin us in the future.

Cheers,
John