The Dark Side of the Conjugate Match

Discussion in 'General Technical Questions and Answers' started by KL7AJ, Mar 12, 2010.

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  1. W5DXP

    W5DXP Ham Member QRZ Page

    Of course, that's a pretty complicated question so let's see what we know about electronic system physics. Let's say we have a matched system and switch the impedance of the load to a mismatched condition.

    You seem to agree that the newly arrived reflected voltage/current phasors can change the slope of the load-line in the source which causes conditions to change back upstream, as you described. There is necessarily something flowing back upstream delivering information to the other stages at the speed of light in the medium. What is the nature of that electronic communications?

    If that communications impulse is traveling at the speed of light in the medium, the communications must necessarily be in the form of photons because electrons cannot travel that fast and there is no other carrier of electronic information besides photons that could accomplish that information transfer in a simple electronics circuit. (There may be other esoteric quantum effects that can accomplish that information transfer but I believe we can ignore such for our discussion here).

    Now we need to make a list of all phenomenon capable of transferring information back upstream providing feedback to a number of electronic circuits at the speed of light in the medium. There are only two directions of RF energy flow in a circuit, forward and rearward. What do we call photons that are traveling rearward? Reflected energy? Using the process of elimination, what else could it be?

    Seems to me that not only do the incident reflections cause a direct change in the load-line of the source, but also ripple back through the drive circuitry to cause a further indirect change in that same load-line.

    Ask yourself, can a load provide load information back to a source at faster than the speed of light? The lumped-circuit model says yes, but it is true? If the load cannot possibly provide load information back to the source at faster than light speed, exactly what is known to physics that can travel rearward at the speed of light? - Process of elimination.
     
  2. G3TXQ

    G3TXQ Ham Member QRZ Page

    Cecil,

    Taken to extreme, then, that change in the PA loadline will "ripple back" to cause a change in the PSU load, to the incoming mains supply, and to the load on the utility company generating station.

    I reckon it's going to take many more postings from you to convince readers that the reflected wave on the TL "penetrates" back as far as the generating station. But I see that is where your argument leads.

    73,
    Steve G3TXQ
     
  3. W8JI

    W8JI Ham Member QRZ Page

    Walt,

    Of course, but sometimes it is better to let it go.

    The only thing continuing does is dilute everything of real value in the thread by filling it with noise.

    73 Tom
     
  4. W5DXP

    W5DXP Ham Member QRZ Page

    Now just wait, Steve, someone is going to accuse me of believing that because you posted it. :) Nope sorry, that's not what I am saying at all. Here's what I am saying:

    Everywhere there is a backwards upstream effect, it is caused by backwards traveling energy that we tend to label "reflected". Otherwise, what caused the effect?

    At the point where the backwards upstream effect disappears and ceases to exist, the backwards traveling energy has undergone reflection, refraction, interference, conversion, or dissipation. Since it disappears as reflected energy, it cannot possibly make it all the way back to the generating station.

    In no way am I saying or implying that reflected energy makes it all the way back to the generating station. At every point where the backwards traveling energy has an effect, it exists at that point. At any point where the backwards traveling energy doesn't have an effect, something has happened to it and it doesn't exist at that point. Of the number of things that could possibly happen to it, those things must obey the laws of physics.
     
  5. W5DXP

    W5DXP Ham Member QRZ Page

    I'm not sure there is a disagreement, Walt, just a misunderstanding of what I have said. You seem to think that I have said reflected energy from the load is always what changes the load-line and I never said that as a general statement. I could have been talking about a specific example.

    IC-706---SWR meter---Tuner------feedline-----------load

    The SWR meter indicates zero reflected power when matched.

    Now leave every thing else the same and de-tune the tuner.

    The SWR meter will indicate reflected power, i.e. reflected energy flowing back into the IC-706 and changing its load-line. It doesn't matter where that reflected energy comes from, it is still reflected energy that is feeding back into the IC-706 and changing its load-line. I have never said the the reflected energy that changes the source's load-line must come from the load. In fact, some mismatched systems have zero energy reflected from from the load.
     
    Last edited: Sep 24, 2010
  6. W5DXP

    W5DXP Ham Member QRZ Page

    It's exactly the same configuration, Walt. Instead of causing a Z0-mismatch by de-tuning the tuner, you are causing a Zg-mismatch by de-tuning the pi-network. If you had a reflected power meter calibrated for Zg, you would be able to detect the reflection from the de-tuning point back to the tube. In both examples, reflections from the mistuned networks are causing reflected energy to be incident upon the source. The reflection just happens super fast (but not faster than the speed of light).

    Please ask yourself, how long does it take for the tube to detect that the pi-network has been mistuned? Maybe one nanosecond? Exactly what information traveled from the mistuned pi-network back to the tube during that one nanosecond? Is there any other plausible explanation besides a reflection? This is not a trick question. Exactly how is the de-tuning information communicated back to the tube in real-world time?

    In my example, the IC-706 knows that the tuner has been mistuned through reflected energy. In your example, how does the tube know that you have de-tuned the pi-network if not by reflected energy feedback from the de-tuning point back to the tube? What other mechanism of feedback exists from the pi-network back to the tube except reflected energy?

    What is the exact mechanism for communicating the mistuning of the pi-network back to the tube in real-world time if it is not a reflection from the mistuning point? I thought you would be glad that the answer is Reflections. :)
     
  7. W5DXP

    W5DXP Ham Member QRZ Page

    Walt, please define "directly connected" while remembering that the dummy load and the pi-network cannot possibly occupy the same space in the real world. If they cannot occupy the same space in the real world then there is a speed-of-light limit in the information-transfer delay between them. That delay, no matter how small it may be, is all important since the lumped-circuit model mistakenly presumes zero delay at faster than light speeds which is impossible in the real world. (Out of respect, I must confess that I am leading you down the primrose path.) Hope you don't mind.

    Again I ask, how does the tube "know" that that the network has changed without some sort of feedback (reflections) from the network? The only feedback that I know of is reflected energy. What is this other (so far) undefined feedback mechanism that you are promoting? Please explain.
     
  8. W8JI

    W8JI Ham Member QRZ Page

    This is what happens with speed of light and the loading coil. A person invents an argument or statement and attributes it to the other person who said or implied no such thing.

    Everyone knows you did not and would not say that. It is just "baiting" to force a continued argument.

    By now, no one is learning a thing from this and all the posts since a few pages ago are just filling the thread with noise that will hurt anyone actually trying to learn.

    73 Tom
     
  9. W5DXP

    W5DXP Ham Member QRZ Page

    Tom, with all due respect, here's the proof that I am not inventing arguments.

    A quote from Dr. Corum's class notes:

    "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 (all regions of the universe can be communicated with instantaneously)."

    It is obvious that you, Walt, and many others are using the lumped-circuit model as part of your argument. The lumped-circuit model presupposes faster-than-light propagation, whether you and others realize it or not. Therefore, anyone who uses the lumped-circuit model, whether he realizes it or not, is presupposing (and thus supporting) faster than light propagation.

    Example: A switchable 50/100 ohm dummy load attached directly to the RF output connector of an IC-706.

    IC-706---50/100 ohm switchable dummy load

    With the 50 ohm dummy load switched in, the source sees its designed-for load and adjusts its load-line to that value. In the IC-706, the transistor load-line is obviously something besides 50 ohms and there is filtering and impedance transformation taking place between the source transistors and the output connector. There is a measurable delay through the filtering and impedance transformation circuitry. The actual delay is not important but let's assume the delay is 100 ns, i.e. it takes the forward field/wave from the source 100 ns to reach the RF output connector traveling at the speed of light in the medium. Now let's switch the dummy load from 50 ohms to 100 ohms.

    You, Walt, and many others appear to argue that there are no reflections and the load-line simply changes to its new value without delay. When you use that lumped-circuit argument you are admitting that you (1) believe in faster than light propagation or (2) believe that the source and load occupy the same space. If you admit that there is a delay, you need to explain what causes the delay and exactly what it is that is being delayed based on the fact of physics that no other kind of energy exists between the source's load-line and RF output connector except forward moving energy and reverse moving energy.

    To the best of my knowledge, the only explanation that obeys the laws of physics is that when the 100 ohm dummy load is switched in, it causes a reflection back into the IC-706. It takes 100 ns (at the speed of light in the medium) for the source to "know" that the dummy load has changed from 50 ohms to 100 ohms. A reflected field/wave is the only explanation (of which I am aware) that obeys the known laws of physics. The magnitude and phase of the reflection are easily calculated based on the V/I ratio of 50 ohms across the 50 ohm dummy load and 100 ohms across the 100 ohm dummy load.

    Fortunately, the delay can be easily measured. What causes the delay? Exactly what is being delayed? What else besides speed-of-light feedback from the new 100 ohm load could cause the load-line to change 100 ns after the load is switched? What mechanism is involved in that feedback if not in the form of a reflected field/wave? Please be specific.

    So you see, I am not making things up. Everyone who asserts that there are no reflections, i.e. no feedback, from a 100 ohm dummy load tied directly to the RF output connector on an IC-706 believes in faster-than-light information transfer, whether they realize it or not. Anyone who switches from the distributed network model to the lumped-circuit model at the transmitter's RF output connector is supporting the faster-than-light concept, whether they realize it or not.

    And please, let's have a gentlemanly discussion and avoid personal attacks.
     
    Last edited: Sep 25, 2010
  10. W5DXP

    W5DXP Ham Member QRZ Page

    Point is, that is not a direct connection. There is a distance between the dummy load and the source. The distance causes a speed-of-light delay in the feedback from the dummy load to the source. Exactly what is the nature of that absolutely necessary speed-of-light feedback from the dummy load to the source? What is the carrier of that feedback information? These are very basic, simple questions.

    Please think outside of the box and read my reply to Tom.

    Is the change in RL communicated back to the source instantaneously, i.e. faster than the speed of light? If not, what carries the cap change information back to the source at the speed of light? If there is any delay, some sort of carrier (field/wave/particle) must necessarily exist.

    The source and the capacitor are not in the same place. There is a delay from the time the cap value is changed to the time the source becomes aware of the change, i.e. there is obviously some sort of feedback from the capacitor to the source. What is the exact nature of that feedback?

    The feedback cannot be electrons because electrons cannot travel that fast.

    The feedback cannot be instantaneous because that would violate the speed-of-light limitation.

    Since the feedback impulse is known to travel at the speed-of-light in the medium, it must be something capable of traveling at the speed-of-light and that fact of physics limits the possibilities of what it might be.

    To the best of my knowledge, given the electronic circuits involved, the carrier of the feedback information cannot be anything except RF fields/waves/photons. What do we call fields/waves/photons that are traveling toward the source at the speed-of-light in the medium.

    We call them reflections. Look all around you. Everything that you see that is not a source of light is an EM reflection. EM reflections are everywhere including inside transmitters.
     
    Last edited: Sep 25, 2010
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