Transmitter Output Impedance
 

On May 18, 9:41*am, Wimpie wrote:
Applying Cecil's rules, you and I are bad engineers/designers, ...

Are false assertions really necessary or helpful?
--
73, Cecil, w5dxp.com

Transmitter Output Impedance
 

On 18 mayo, 17:26, Cecil Moore wrote:
On May 18, 9:41*am, Wimpie wrote:

Applying Cecil's rules, you and I are bad engineers/designers, ...

Are false assertions really necessary or helpful?
--
73, Cecil, w5dxp.com

Hello Cecil,

You keep on luring us (and others) into non-relevant discussions.
Snippet from your posting to Tom:

From the time (t0) that a PA first outputs a Zg signal to the time
(t1) that the PA senses its load impedance is NOT zero time. How does
the PA know what its load impedance really is when it is not Zg?
Einstein's spooky action at a distance? No, feedback from the load.

Obviously, the PA receives some sort of feedback in real time. What is
the nature of that feedback? What can it be besides feedback energy
reflected from the load? (not in zero time, but at the speed of
light). In the real world, it takes measurable time for the forward
energy to reach the load and measurable time for the reflected
feedback (if any) to arrive back at the PA. The load seen at the PA
source is always an E/I ratio, i.e. a lossless image impedance that
always experiences a delay if it is not equal to Zg, i.e. it usually
contains reflected energy.

There must be some (for us hidden) reason to do this.

We are discussing near steady state sinusoidal signals, so amplitude
and phase can only vary slowly (if not, other amateurs would not be
happy with you). Especially in case of manual load pulling, it doesn't
matter when there is a back and forth delay of 100 us (that is 10 km
of coaxial cable!!). All such delay actions are fully covered by the
concept of impedance (and steady state transmission line theory). We
are not discussing wide band systems where a reflected signal may be
uncorrelated with the actual output signal.

Wim
PA3DJS
www.tetech.nl

Transmitter Output Impedance
 

On May 18, 6:11*am, Cecil Moore wrote:
On May 18, 12:33 am, K7ITM wrote:

I'm _still_ trying to figure out _why_ anyone would care about the
output impedance of a PA of the sort used at HF to drive antennas.
Nobody has ever convinced me that it matters at all, except perhaps as
academic interest.

Nobody is questioning the efficacy of design methods. Whatever works,
works. What we are discussing is indeed only of academic interest.
Knowing whether my IC-706 is conjugately matched or not does not
affect its operation at all.

From the time (t0) that a PA first outputs a Zg signal to the time
(t1) that the PA senses its load impedance is NOT zero time. How does
the PA know what its load impedance really is when it is not Zg?
Einstein's spooky action at a distance? No, feedback from the load.

Obviously, the PA receives some sort of feedback in real time. What is
the nature of that feedback? What can it be besides feedback energy
reflected from the load? (not in zero time, but at the speed of
light). In the real world, it takes measurable time for the forward
energy to reach the load and measurable time for the reflected
feedback (if any) to arrive back at the PA. The load seen at the PA
source is always an E/I ratio, i.e. a lossless image impedance that
always experiences a delay if it is not equal to Zg, i.e. it usually
contains reflected energy.
--
73, Cecil, w5dxp.com

Cecil, just HOW do you propose to MEASURE the effect you describe, as
seen at the transmitter's output port, using only our HF ham
transmitter/PA that transmits a signal with a maximum bandwidth of
perhaps 10kHz? If it is going to have the dire consequences you
suggested a few postings ago, then it must be trivial to
measure...unfortunately, I don't see how, and that bugs me, as one who
strives to provide accurate, sophisticated measurement technology to
engineers.

Perhaps you missed it, but nobody is disagreeing that the mechanism
for establishing a load impedance is reflections in the system of
lines and lumped loads attached to the PA output. We are simply
saying that, for the bandwidth signals involved, you'll be extremely
hard-pressed to distinguish between a load consisting of any number of
transmission line segments, along with one or many lumped loads
wherever you want along those line segments, and a simple equivalent
series RLC.

I suppose it will be lost on most of the lurkers, but it's a bit of a
bad joke to deny that one can make valid PA output impedance
measurements with a signal very slightly off-frequency (less than
1kHz), and then claim that reflections in a system of maybe a couple
hundred feet of coax makes a major difference in how the load behaves
as compared with a lumped RLC.

Cheers,
Tom

Transmitter Output Impedance
 

On May 18, 11:56*am, K7ITM wrote:
Cecil, just HOW do you propose to MEASURE the effect you describe, as
seen at the transmitter's output port, using only our HF ham
transmitter/PA that transmits a signal with a maximum bandwidth of
perhaps 10kHz?

I don't have a proposal and am just pointing out some of the technical
problems associated with some of the methods being proposed. FYI, when
one uses a model that presupposes faster than light propagation speeds
to try to explain something happening in the real world, one should
expect some skepticism - unless one can prove that he is using
entangled photons. :-)
--
73, Cecil, w5dxp.com

Transmitter Output Impedance
 

On 18 mayo, 19:46, Cecil Moore wrote:
On May 18, 11:56*am, K7ITM wrote:

Cecil, just HOW do you propose to MEASURE the effect you describe, as
seen at the transmitter's output port, using only our HF ham
transmitter/PA that transmits a signal with a maximum bandwidth of
perhaps 10kHz?

I don't have a proposal and am just pointing out some of the technical
problems associated with some of the methods being proposed. FYI, when
one uses a model that presupposes faster than light propagation speeds
to try to explain something happening in the real world, one should
expect some skepticism *- unless one can prove that he is using
entangled photons. :-)
--
73, Cecil, w5dxp.com

Hello Cecil,

Could you please explain why the lumped circuit approach used by many
people across the world presupposes faster than light propagation (as
I can't)?

In my opinion it only presupposes that speed of light is not of
importance and if it does, you can model that very easy by adding some
additional lumped components in many cases.

Just take a circuit diagram of your rig, lumped components all over
the place and if there are coaxial cables, they are just for
transporting a signal from one place to another place. Did you ever
used a circuit simulator, if so, did you model every capacitor,
resistor, etc with a transmission line model?

You may evaluate for yourself a CLC section and see what the output
versus input does. Of course you could also put it in some circuit
simulator. And again you are trying to introduce non-relevancy into
the topic.

Wim
PA3DJS
www.tetech.nl

Transmitter Output Impedance
 

On May 18, 2:33*pm, Wimpie wrote:
Could you please explain why the lumped circuit approach used by many
people across the world presupposes faster than light propagation (as
I can't)?

http://hamwaves.com/antennas/inductance/corum.pdf

"The failure of any lumped element circuit model to describe the real
world lies at its core inherent *presupposition*: the speed of light
is assumed infinite in the wave equation."

"Lumped element circuit theory assumes that there are no wave
interference phenomena present, that is - the currents entering and
leaving the circuit element's terminals are identical."

http://www.classictesla.com/download...ed_failure.pdf

"In fact, lumped-element circuit theory inherently employs the
cosmological presupposition that the speed of light is infinite, as
every EE sophomore should know."

"Lumped circuit theory fails because it's a theory whose
presuppositions are inadequate. Every EE in the world was warned of
this in their first sophomore circuits course."

Give me some time and I will compose an example based on EZNEC results
for a lumped inductor vs a helical inductor of equal inductance. The
results are nowhere near the same.
--
73, Cecil, w5dxp.com

Transmitter Output Impedance
 

On May 18, 4:05*pm, Cecil Moore wrote:
Give me some time and I will compose an example based on EZNEC results
for a lumped inductor vs a helical inductor of equal inductance. The
results are nowhere near the same.

The example is a 4 MHz series circuit with a 100v source, a 72uH
inductance, and a 2570 ohm resistor.

Using a 72uH lumped inductance, the current is the same all around the
circuit and is 0.032 amps at -24 degrees, i.e. the source current is
24 degrees out of phase with the source voltage.

Using a 72uH helical inductance, the source current is 0.039 amps at
-0.02 degrees, i.e. in phase with the source voltage. The load current
is 0.039 amps at -42.4 degrees. The phase shift through the helical
inductor is more than 40 degrees.

As you probably know, the phase angles of superposed waves have a
drastic effect on the resulting impedance.
--
73, Cecil, w5dxp.com

Transmitter Output Impedance
 

On 18 mayo, 23:39, Cecil Moore wrote:
On May 18, 4:05*pm, Cecil Moore wrote:

Give me some time and I will compose an example based on EZNEC results
for a lumped inductor vs a helical inductor of equal inductance. The
results are nowhere near the same.

The example is a 4 MHz series circuit with a 100v source, a 72uH
inductance, and a 2570 ohm resistor.

Using a 72uH lumped inductance, the current is the same all around the
circuit and is 0.032 amps at -24 degrees, i.e. the source current is
24 degrees out of phase with the source voltage.

Using a 72uH helical inductance, the source current is 0.039 amps at
-0.02 degrees, i.e. in phase with the source voltage. The load current
is 0.039 amps at -42.4 degrees. The phase shift through the helical
inductor is more than 40 degrees.

As you probably know, the phase angles of superposed waves have a
drastic effect on the resulting impedance.
--
73, Cecil, w5dxp.com

Hello Cecil,

Can you describe the complete setup, or post a simple drawing
(including ground path, source and load and position of current and
voltmeters). I think that I can model it by using a lumped inductor
with 2 capacitors (in fact a section of an LC delay line). What is the
total wire length (just curious to know)?

72 uH, seems large for a matching inductor in a PA (at say 4 MHz, just
22 pF to resonate).


Wim
PA3DJS
www.tetech.nl

Transmitter Output Impedance
 

On 5/18/2011 4:05 PM, Cecil Moore wrote:
On May 18, 2:33 pm, wrote:
Could you please explain why the lumped circuit approach used by many
people across the world presupposes faster than light propagation (as
I can't)?

http://hamwaves.com/antennas/inductance/corum.pdf

"The failure of any lumped element circuit model to describe the real
world lies at its core inherent *presupposition*: the speed of light
is assumed infinite in the wave equation."

"Lumped element circuit theory assumes that there are no wave
interference phenomena present, that is - the currents entering and
leaving the circuit element's terminals are identical."

http://www.classictesla.com/download...ed_failure.pdf

"In fact, lumped-element circuit theory inherently employs the
cosmological presupposition that the speed of light is infinite, as
every EE sophomore should know."

"Lumped circuit theory fails because it's a theory whose
presuppositions are inadequate. Every EE in the world was warned of
this in their first sophomore circuits course."

Give me some time and I will compose an example based on EZNEC results
for a lumped inductor vs a helical inductor of equal inductance. The
results are nowhere near the same.
--
73, Cecil, w5dxp.com


I'm not speaking for Wim, but I think we are both saying the following:

* You have a known load
* You have a transmission line with known characteristics
* Is is possible to use a Smith chart to get the impedance at the input
to the transmission line.
* We now know the load applied to the transmitter.

All we need to know we get from the chart. We admit that reflections are
responsible for the impedance transformation from load to line input.
But, we don't need to know anything about the reflection details, energy
content of the line, nor how light would like it.

So, we are saying that the load at the line input can be viewed as a
lumped circuit. So now we have a transmitter loaded with a lumped
circuit for further analysis.

That's all. It's simple.

John

Transmitter Output Impedance
 

On May 18, 5:21*pm, Wimpie wrote:
Can you describe the complete setup, or post a simple drawing
(including ground path, source and load and position of current and
voltmeters). I think that I can model it by using a lumped inductor
with 2 capacitors (in fact a section of an LC delay line). What is the
total wire length (just curious to know)?

Do you have EZNEC? If so, I can just upload the .EZ files to my web
page.

72 uH, seems large for a matching inductor in a PA (at say 4 MHz, just
22 pF to resonate).

:-) It's just what I had available - an EZNEC version of a Texas
Bugcatcher 80m loading coil.
--
73, Cecil, w5dxp.com