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#61
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On May 19, 5:22*pm, Wimpie wrote:
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? You apparently have not comprehended what I am trying to say. When one is designing a piece of equipment, whatever works, works. Please don't confuse design/analysis techniques and rule-of-thumb shortcuts with the underlying principles supporting the laws of physics. Enumerating all the design techniques in the world does not tell us anything about what is happening in reality to those photonic fields and waves that necessarily must obey the laws of physics. Even DC impulses travel at the speed of light. Electron drift velocity is much, much slower than the speed of light. Everything EM is photonic in nature. Photons must obey the laws of physics known to exist for photons. There is simply no getting around that fact. All of the magical thinking, hand-waving, design/analysis shortcuts, and rules-of-thumb in the world are not going to change those facts of physics. If you do not understand those physical limitations (including. the difference between the two IEEE definitions of impedance) you will never understand what is actually happening in reality inside (or outside of) an RF source. I don't know what else to say. -- 73, Cecil, w5dxp.com |
#62
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On 20 mayo, 14:42, Cecil Moore wrote:
On May 19, 5:22*pm, Wimpie wrote: 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? You apparently have not comprehended what I am trying to say. When one is designing a piece of equipment, whatever works, works. Please don't confuse design/analysis techniques and rule-of-thumb shortcuts with the underlying principles supporting the laws of physics. Enumerating all the design techniques in the world does not tell us anything about what is happening in reality to those photonic fields and waves that necessarily must obey the laws of physics. Even DC impulses travel at the speed of light. Electron drift velocity is much, much slower than the speed of light. Everything EM is photonic in nature. Photons must obey the laws of physics known to exist for photons. There is simply no getting around that fact. All of the magical thinking, hand-waving, design/analysis shortcuts, and rules-of-thumb in the world are not going to change those facts of physics. Hello Cecil, When one knows the physics well, one knows what to take into account and what to left out, just to finish the job efficiently. It seems you don't understand that principle. Is this some lack of understanding physics? Do you really believe that when designing an optical detector (completely off-topic) I don't bother about noise due to quantisation? If you do not understand those physical limitations (including. the difference between the two IEEE definitions of impedance) you will never understand what is actually happening in reality inside (or outside of) an RF source. I don't know what else to say. -- 73, Cecil, w5dxp.com Regarding PA's and IEEE definitions, I don't get paid for my knowledge (if present?), but just for delivering what has been agreed. You introduced photons here; I think you may also introduce thermodynamics of electrons as that may be of more importance at our frequencies. I do not violate agreed laws of physics, but only leave out higher order effects that are insignificant in my opinion. Wim PA3DJS www.tetech.nl |
#63
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On May 20, 8:25*am, Wimpie wrote:
When one knows the physics well, one knows what to take into account and what to left out, just to finish the job efficiently. Again, just getting the "job" done is completely irrelevant. This was an unsuccessful quest for knowledge and understanding of the nature of an RF source - so I will say, "73", Cecil, w5dxp.com |
#64
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On 20 mayo, 16:47, Cecil Moore wrote:
On May 20, 8:25*am, Wimpie wrote: When one knows the physics well, one knows what to take into account and what to left out, just to finish the job efficiently. Again, just getting the "job" done is completely irrelevant. This was an unsuccessful quest for knowledge and understanding of the nature of an RF source - so I will say, "73", Cecil, w5dxp.com He JOB = finding a satisfying answer to the thoughts laid down by Salmonella. Understanding the nature of an RF source, can be mastered very efficiently without: photons, momentum, extensive transmission line theory, Poynting vector, etc. You may visit VK1OD's website ( www.vk1od.net ) for ways how to explain things. Wim PA3DJS www.tetech.nl |
#65
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On May 20, 10:27*am, Wimpie wrote:
Understanding the nature of an RF source, can be mastered very efficiently without: photons, ... :-) :-) :-) And that's exactly how we get 3ns delays through foot long 75m loading coils, EM wave energy that stands perfectly still in standing waves, and reflected waves somehow existing devoid of any energy at all. |
#66
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On May 20, 6:25*am, Wimpie wrote:
On 20 mayo, 14:42, Cecil Moore wrote: On May 19, 5:22*pm, Wimpie wrote: 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? You apparently have not comprehended what I am trying to say. When one is designing a piece of equipment, whatever works, works. Please don't confuse design/analysis techniques and rule-of-thumb shortcuts with the underlying principles supporting the laws of physics. Enumerating all the design techniques in the world does not tell us anything about what is happening in reality to those photonic fields and waves that necessarily must obey the laws of physics. Even DC impulses travel at the speed of light. Electron drift velocity is much, much slower than the speed of light. Everything EM is photonic in nature. Photons must obey the laws of physics known to exist for photons. There is simply no getting around that fact. All of the magical thinking, hand-waving, design/analysis shortcuts, and rules-of-thumb in the world are not going to change those facts of physics. Hello Cecil, When one knows the physics well, one knows what to take into account and what to left out, just to finish the job efficiently. It seems you don't understand that principle. Is this some lack of understanding physics? Do you really believe that when designing an optical detector (completely off-topic) I don't bother about noise due to quantisation? If you do not understand those physical limitations (including. the difference between the two IEEE definitions of impedance) you will never understand what is actually happening in reality inside (or outside of) an RF source. I don't know what else to say. -- 73, Cecil, w5dxp.com Regarding PA's and IEEE definitions, *I don't get paid for my knowledge (if present?), but just for delivering what has been agreed. You introduced photons here; I think you may also introduce thermodynamics of electrons as that may be of more importance at our frequencies. *I do not violate agreed laws of physics, but only leave out higher order effects that are insignificant in my opinion. Wim PA3DJSwww.tetech.nl Beyond just understanding what parts of the physics theory are important in a particular situation, there's the more general concept of compartmentalizing things. The original question was about transmitter output impedance, and to answer that question, you really don't have to get into interminable discussions about what goes on in some arbitrary load. The only things that matter with respect to the load are the voltage, current and phase between them at the output port of the source. A perfectly valid reason to talk about the load -- what you connect to the source output port -- is how you can configure that load to establish a variety of load conditions so that you can see how the source behaves, and from that, derive the source impedance. In fact, some months past now, Wim and I had some email exchanges about that. The emails were very valuable to me, because they got me thinking about various arrangements of the equipment I have to enable accurate measurements, and brought up points about things that go on _inside_ a typical RF power amplifier that can cause you to measure things inaccurately. For example, an ALC loop with a relatively slow response time could make you think that the amplifier output impedance is quite low if you take measurements more slowly than the response time of the ALC loop. You might even decide that it makes sense to talk about amplifier output impedance as a function of frequency offset relative to the output frequency (or some similar way to talk about the "time response" of the output impedance). It all depends on what you want to _do_ with your output impedance number once you have it, and that's something I don't recall seeing much of in this thread, nor in any of the many previous threads covering the same old ground. Cheers, Tom |
#67
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#68
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On May 20, 1:08*pm, K7ITM wrote:
On May 20, 6:25*am, Wimpie wrote: On 20 mayo, 14:42, Cecil Moore wrote: On May 19, 5:22*pm, Wimpie wrote: 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? You apparently have not comprehended what I am trying to say. When one is designing a piece of equipment, whatever works, works. Please don't confuse design/analysis techniques and rule-of-thumb shortcuts with the underlying principles supporting the laws of physics. Enumerating all the design techniques in the world does not tell us anything about what is happening in reality to those photonic fields and waves that necessarily must obey the laws of physics. Even DC impulses travel at the speed of light. Electron drift velocity is much, much slower than the speed of light. Everything EM is photonic in nature. Photons must obey the laws of physics known to exist for photons. There is simply no getting around that fact. All of the magical thinking, hand-waving, design/analysis shortcuts, and rules-of-thumb in the world are not going to change those facts of physics. Hello Cecil, When one knows the physics well, one knows what to take into account and what to left out, just to finish the job efficiently. It seems you don't understand that principle. Is this some lack of understanding physics? Do you really believe that when designing an optical detector (completely off-topic) I don't bother about noise due to quantisation? If you do not understand those physical limitations (including. the difference between the two IEEE definitions of impedance) you will never understand what is actually happening in reality inside (or outside of) an RF source. I don't know what else to say. -- 73, Cecil, w5dxp.com Regarding PA's and IEEE definitions, *I don't get paid for my knowledge (if present?), but just for delivering what has been agreed. You introduced photons here; I think you may also introduce thermodynamics of electrons as that may be of more importance at our frequencies. *I do not violate agreed laws of physics, but only leave out higher order effects that are insignificant in my opinion. Wim PA3DJSwww.tetech.nl Beyond just understanding what parts of the physics theory are important in a particular situation, there's the more general concept of compartmentalizing things. *The original question was about transmitter output impedance, and to answer that question, you really don't have to get into interminable discussions about what goes on in some arbitrary load. *The only things that matter with respect to the load are the voltage, current and phase between them at the output port of the source. A perfectly valid reason to talk about the load -- what you connect to the source output port -- is how you can configure that load to establish a variety of load conditions so that you can see how the source behaves, and from that, derive the source impedance. *In fact, some months past now, Wim and I had some email exchanges about that. The emails were very valuable to me, because they got me thinking about various arrangements of the equipment I have to enable accurate measurements, and brought up points about things that go on _inside_ a typical RF power amplifier that can cause you to measure things inaccurately. *For example, an ALC loop with a relatively slow response time could make you think that the amplifier output impedance is quite low if you take measurements more slowly than the response time of the ALC loop. *You might even decide that it makes sense to talk about amplifier output impedance as a function of frequency offset relative to the output frequency (or some similar way to talk about the "time response" of the output impedance). *It all depends on what you want to _do_ with your output impedance number once you have it, and that's something I don't recall seeing much of in this thread, nor in any of the many previous threads covering the same old ground. Cheers, Tom I'm trying to locate the John Smith who signs his posts with 'js'. Does any one know his call sign? Or perhaps his email address? Thanks, Walt, W2DU |
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Transmitter Output Impedance | Antenna |