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Richard Harrison wrote:
"If the transmitting antenna were to radiate energy isotropically-that ... -the power flow through unit area at a distance R, ... What virtually every engineer means when he says, "power flow", is, "the power (energy per unit-time) associated with the energy flow". Knowing Jim, he would also probably argue that the sun doesn't rise - that instead, the earth rotates. However, most weather forcasts on TV gives the times for sunrise and sunset. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Cecil, W5DXP wrote:
"What is it about, "...all "lost" reflected intensity will appear as enhanced intensity in the transmitted beam." that you guys don`t understand?" A quarter-wave intermediate impedance line section can perfectly match different resistances at its ends. When a match exists at the end of a line, there is no discontinuity and the line appears as if infinite. There is no reflection from an impedance match. It`s a multiplicity of waves which seem gratuitous. Best regards, Richard Harrison, KB5WZI |
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Richard Harrison wrote: Jim Kelley wrote: "That`s because power doesn`t propagate, I hasten to add - neither do Poynting vectors.: Some world-class experts disagree with Jim. Here is a sample quotation using the words "power flow". From E.M. Purcell writing about "Antenna Gain and Receiving Cross Section" on page 19 of "Radar System Engineering" edited by Louis M. Ridenour: "If the transmitting antenna were to radiate energy isotropically-that is, uniformly in all directions-the power flow through unit area at a distance R, from the antenna could be found by dividing P, the total radiated power, by 4piRsquared." Best regards, Richard Harrison, KB5WZI There's nothing wrong with calculating the power per unit area at any point in a transmission line. I'm sorry if I gave some other impression. The problem I have is with believing that the calculated value propagates as if it were an electromagnetic field. The Poynting vector is useful for making calculations, but it not a useful tool for explaining the behavior of natural phenomenon. 73, ac6xg |
Cecil Moore wrote: Richard Harrison wrote: "If the transmitting antenna were to radiate energy isotropically-that ... -the power flow through unit area at a distance R, ... What virtually every engineer means when he says, "power flow", is, "the power (energy per unit-time) associated with the energy flow". Knowing Jim, he would also probably argue that the sun doesn't rise - that instead, the earth rotates. However, most weather forcasts on TV gives the times for sunrise and sunset. Yea, somebody around here once said that I would probably step out of the shower to take a pee. To that I say why would anyone step into it to take one? ;-) 73, ac6xg |
Walt, W2DU wrote:
"A semantic problem with the term "Power Flow" also fuels the erroneous belief that reflected power is fictitious." Another world-class expert has agreed that power flows. Energy may or may not flow. It is the accumulation of flows that you pay for on your monthly electric bill. Power is the rate of delivering energy (doing wotk), so it can`t stand still. No power flow, no work. Take it from W2DU. Reflections are important. Reflections occur at discontinuities. To the extent that voltage and current are in-phase, they mean real power. Zo is resistive in a practical r-f transmission line. Incident and reflected waves both propagate on the line with their individual voltages and currents locked in-phase. The sum of incident and reflected waves can`t be relied upon to indicate power, but infividually each wave can indicate true power. The reflected wave interferes with the incident wave to produce standing waves. These represent the impedance distribution along the line. They do not represent variation of power in the wave in eather direction. Best regards, Richard Harrison, KB5WZI |
Cecil Moore wrote: If the power associated with an EM pulse is not in the pulse, where is it? According to definition, the 'effect' of power is something which can be realized at a place where energy either is being transferred from, or transferred to. The amount of effect is proportional to the rate at which energy is transfered. But power is not the thing which is being transferred from one place to another. Often times though we want to know the rate at which energy is being transferred to or from one place to another, and there are mechanisms we can use to measure things that manifest themselves in proportion to that quantity. But some folks forget that it's just a tool for making accurate predictions about things, and start to believe some odd things about the behavior of nature. One must be careful not to mistake a physical quantity for a physical entity. 73, ac6xg |
Walter Maxwell wrote: The same problem exists with the term "power flow." Engineering textbooks define power as the "quantity of energy passing a point per unit time." Thus, power does not flow--energy flows. However, except when reciting the definition of power, textbooks and journals on wave propagation use the term "power flow" almost exclusively, with only an occasional use of "energy flow." As with "current flow," we know what is meant because of the common usage which generally overshadows the strict definition." Perhaps this explanation will satisfy Jim, but perhaps not. We'll see. Walt, W2DU Hi Walt, I am familiar with the common usage of the expression 'power flow' and of course the Poynting vector. I've been explaining that "energy flows - not power" on this newsgroup for 4 years and have gotten nothing but grief for it. I think it will be more interesting to see whether your explanation will satisfy the others. 73, ac6xg |
Jim Kelley wrote:
"That`s because power doesn`t propagate, and hasten to add - neither do Poynting vectots." One could make a long list of serious authors who freely treat power as moving energy. I namrd Ktaus, Ridenour, Purcell, and Walter Maxwell. Terman was another world-class expert who was unafraid of the word "power". On page 76 of his 1955 edition he wrote: "Alternatively, a load impedance may be matched to a source of power in such a way as to make the power delivered to the load a maximum (The power delivered to the load under these conditions is termed the available power of the power source). This is accomplished by making the load impedance the conjugate of the generator impedance as defined by Thevenin`s theorem. That is, the load impedance must have the same magnitude as the generator impedance, but the phase angle of the load is the negative of the phase angle of the generator impedance." I have not yet seen a copy of "Reflections", but would bet that W2DU says the same thing, perhaps in fewer and shorter words. Best regards, Richard Harrison, KB5WZI |
Richard Clark wrote:
Anyway, the optical analogue has proven to be a bust when I demonstrated that reflection products do persist. This is not the place to hash over that again. If you wish, you can consult my original posting and the follow-ons for details. But in your "proof", you superposed powers which is a no-no. When 111.1mW interfers with 87.78mW, the result is not (111.1-87.78). Since the associated E-fields are 180 degrees out of phase, the power equation must take the interference into account. Pref1 = 111.1mW + 87.78mW - 2* sqrt(111.1*87.78) Pref1 = 111.1mW + 87.78mW - 197.5mW = 1.38mW You subtract 87.78 from 111.1 and get 23.32. That value is almost 17 times too high. All your math after that is invalid. All except 1.38mW of reflections are canceled by that first internal reflection. Your value of 23.32 is simply wrong. RF engineers usually convert to voltage, perform the superposition, and then calculate the total power. One doesn't have that luxury when dealing with light so the power (irradiance) equations must be used to obtain the correct results. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Jim Kelley wrote:
I am familiar with the common usage of the expression 'power flow' and of course the Poynting vector. I've been explaining that "energy flows - not power" on this newsgroup for 4 years and have gotten nothing but grief for it. I think it will be more interesting to see whether your explanation will satisfy the others. Would you agree that the amount of energy passing a point in a unit-time is power? -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Richard Harrison wrote:
Jim Kelley wrote: "That`s because power doesn`t propagate, and hasten to add - neither do Poynting vectots." One could make a long list of serious authors who freely treat power as moving energy. I namrd Ktaus, Ridenour, Purcell, and Walter Maxwell. You can add Walter Johnson, Simon Ramo, and John Whinnery to that list. "Power in the reflected wave" is commonly mentioned. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Jim Kelley wrote:
I am familiar with the common usage of the expression 'power flow' and of course the Poynting vector. I've been explaining that "energy flows - not power" on this newsgroup for 4 years and have gotten nothing but grief for it. You are technically correct but it doesn't matter. The Sun will rise tomorrow even if the Sun is fixed in space. I'll even bolster your argument. RF energy moves at the speed of light in the transmission line. The power meter is standing still compared to the transmission line. If the power meter were moving with the energy at the speed of light, it wouldn't work at all. Does that help? :-) -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Jim Kelley wrote:
Cecil Moore wrote: If the power associated with an EM pulse is not in the pulse, where is it? According to definition, the 'effect' of power is something which can be realized at a place where energy either is being transferred from, or transferred to. Please define "transfer" in this context. The IEEE Dictionary defines "transfer capability - the capacity and ability of a transmission line to allow for the reliable MOVEMENT OF ELECTRIC POWER from an area of supply to an area of need." Emphasis mine. But power is not the thing which is being transferred from one place to another. Jim, we can use your logic to solve most of the racial problems in the USA. Black Americans are not black. White Americans are not white. These statements can be proven beyond any doubt by using a light spectrometer. Therefore, since there are no black people and no white people, there can exist no clash between black culture and white culture. All racial problems are therefore declared solved. Next problem? -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Cecil Moore wrote: Jim Kelley wrote: I am familiar with the common usage of the expression 'power flow' and of course the Poynting vector. I've been explaining that "energy flows - not power" on this newsgroup for 4 years and have gotten nothing but grief for it. I think it will be more interesting to see whether your explanation will satisfy the others. Would you agree that the amount of energy passing a point in a unit-time is power? Or even more to the point: Do you believe the 'amount of motorcycle' passing a point in a unit time is speed? :-) The units speak plainly enough for themselves. Why do you ask me? You're the one who always turns these things into a religious argument over 'belief' systems. 73, ac6xg |
Cecil Moore wrote: Richard Harrison wrote: Jim Kelley wrote: "That`s because power doesn`t propagate, and hasten to add - neither do Poynting vectots." One could make a long list of serious authors who freely treat power as moving energy. I namrd Ktaus, Ridenour, Purcell, and Walter Maxwell. You can add Walter Johnson, Simon Ramo, and John Whinnery to that list. "Power in the reflected wave" is commonly mentioned. Proving what, exactly? That power is "in" a reflected wave? ac6xg |
Cecil Moore wrote:
You are technically correct but it doesn't matter. You just spent 4 years vehemently arguing the exact opposite point of view. It sure seemed to matter to you - before yesterday. RF energy moves at the speed of light in the transmission line. The power meter is standing still compared to the transmission line. If the power meter were moving with the energy at the speed of light, it wouldn't work at all. Does that help? :-) Might be the seed of an idea there for a real nerdy Saturday morning science fiction cartoon. "Cecil and the Power Meters" Now that's the kind of humor that actually merits a smiley face! :-) ac6xg |
Jim Kelley wrote:
The units speak plainly enough for themselves. Why do you ask me? You're the one who always turns these things into a religious argument over 'belief' systems. Jim, there are more references on my side than on yours. Your definitions are esoteric to say the least. My definitions are mainstream IEEE and agree with many authors of RF books and power industry standards. "There is no before and after!" (a quote from one of your emails to me). Would you mind proving that assertion? -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Jim Kelley wrote:
Cecil Moore wrote: You can add Walter Johnson, Simon Ramo, and John Whinnery to that list. "Power in the reflected wave" is commonly mentioned. Proving what, exactly? That power is "in" a reflected wave? Proving that "Power in the reflected wave" is common usage in RF engineering. You are not going to get the human race to stop using the word, "sunrise", no matter what you say or do. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Jim Kelley wrote:
Cecil Moore wrote: You are technically correct but it doesn't matter. You just spent 4 years vehemently arguing the exact opposite point of view. BS! Please don't confuse my ability to act as devil's advocate with what are my basic concepts. I have told you multiple times before over any number of years that I agree with you that power is energy passing a point or plane in a unit of time. That can be easily proven to be true with a little Google research. I'm old-fashioned enough to believe that joules/sec needs a reference measuring point or plane. That's what I was taught in the 50's and that's the concept that I still carry around in my head. What I have said lately is that any number of knowledgeable engineers and authors have an expanded definition of power. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Cecil Moore wrote: Jim Kelley wrote: Cecil Moore wrote: You are technically correct but it doesn't matter. You just spent 4 years vehemently arguing the exact opposite point of view. BS! Now you're vehemently arguing about whether you argued or not. What I have said lately is that any number of knowledgeable engineers and authors have an expanded definition of power. That was never in dispute. You argued that power propagates and reflects, and I explained that it doesn't. Now you're behaving like a child. ac6xg |
Jim Kelley wrote:
You argued that power propagates and reflects, and I explained that it doesn't. Jim, you know that isn't true. After you reviewed my article, I changed every occurence of "reflected power" to "reflected energy" just to satisfy you. You have never been able to back up your assertions about what I have said with any quotes of mine. Wonder why? So once again, I challenge you to produce a quote where I said power propagates and reflects. I have always said that energy propagates and reflects and power is the measurement of that energy flowing past a point. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Jim Kelley wrote:
You argued that power propagates and reflects, and I explained that it doesn't. Jim, here's a posting from last year that proves your assertion to be false. I agreed with you last year that power doesn't flow and isn't reflected. I agreed with you that it is energy that flows and is reflected. I agreed with you that power is measured at a point. Seems an apology is in order. Newsgroups: rec.radio.amateur.antenna From: Cecil Moore Date: Thu, 02 Dec 2004 14:28:20 -0600 Subject: Additional Line Losses Due to SWR Jim Kelley wrote: The crux of the phenomenological problem is that power does not flow or move, nor is it something that is reflected. But energy does flow and move and is something that can be reflected. You can easily see the energy packets using a TDR. Without energy, those pulses wouldn't exist. The energy is obviously in the pulse, where the voltage and current are. And joules of energy flowing past a point is joules/sec, i.e. power, by IEEE definition. -- 73, Cecil http://www.qsl.net/w5dxp -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
On Tue, 02 Aug 2005 16:04:29 -0500, Cecil Moore
wrote: Jim Kelley wrote: Cecil Moore wrote: You can add Walter Johnson, Simon Ramo, and John Whinnery to that list. "Power in the reflected wave" is commonly mentioned. Proving what, exactly? That power is "in" a reflected wave? Proving that "Power in the reflected wave" is common usage in RF engineering. You are not going to get the human race to stop using the word, "sunrise", no matter what you say or do. Jim, I'm sure you'll agree that voltage is reflected, and that current is also reflected. Then isn't the product of voltage and current power? Walt, W2DU |
Walter Maxwell wrote:
Cecil Moore wrote: Proving that "Power in the reflected wave" is common usage in RF engineering. Jim, I'm sure you'll agree that voltage is reflected, and that current is also reflected. Then isn't the product of voltage and current power? I think I understand Jim's point that power is measured relative to a stationary point or plane. The Bird wattmeter is stationary in the transmission line and measures the average energy/time flowing through it. Average power is averaged over at least one complete cycle. It is hard to visualize an average power meter measurement while the meter is moving with the wave - admittedly an esoteric point and not likely to have any effect on common usage. Consider that it is the instantaneous value of voltage and current that is reflected (actually the instantaneous E-field and H-field). The RMS value of voltage and current is not what is actually reflected in reality. But again, shortcuts and common usage rule the day. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Jim Kelley wrote:
"---power does not flow or move, nor is it something that can be reflected." From the Random House American College Dictionary: Power is the ability to do or act. It is the time rate of transferring or transforming energy. It is work done or energy transferred per unit of time. The power to do or act can be moved from one location to another. A power house is an electrical generating station where some other form of energy is converted to electricity which is very flexible in application. From the power house, the power (ability to do or act) is transported by power transmission lines to the places it is used. Since the wavelength at 60 Hz is 5 million meters, (5000 km), power transmission lines aren`t long enough to produce standing waves which are caused by reflections. Radio-frequency transmission lines are often long enough to show the effects of reflections and the standing waves produced by those reflections. Power flows in r-f lines and it is reflected at impedance discontinuities accordimg to the most knowledgeable experts. F.E. Terman is my favorite. Best regards, Richard Harrison, KB5WZI |
Walter Maxwell wrote:
On Tue, 02 Aug 2005 16:04:29 -0500, Cecil Moore wrote: Jim Kelley wrote: Cecil Moore wrote: You can add Walter Johnson, Simon Ramo, and John Whinnery to that list. "Power in the reflected wave" is commonly mentioned. Proving what, exactly? That power is "in" a reflected wave? Proving that "Power in the reflected wave" is common usage in RF engineering. You are not going to get the human race to stop using the word, "sunrise", no matter what you say or do. Jim, I'm sure you'll agree that voltage is reflected, and that current is also reflected. Then isn't the product of voltage and current power? Walt, W2DU I hope I haven't given the impression that I would be unfamiliar with that relationship. I used it in my work practically every day of my life for many years. Here's my best answer to such a question. According to the physics that I've studied, physicists seem to be laboring under the impression that it is the electric and magnetic fields which actually propagate and interact with matter. That interaction can result in, among other things, reflection. The E&H fields manifest themselves within matter as voltages and currents, respectively. Although it is the fields which reflect, it is the resulting voltages and currents that we can most readily measure. From a practical everyday standpoint this distinction makes little or no difference. It is only when we start to describe physical processes such as energy flow that it may become necessary to consider the distinction. And yes, if you take a calculator or slide rule and multiply voltage and current, and make certain assumptions, you can find the rate at which energy is probably being transferred from one place to some other place. But some folks have argued descriptions of physical phenomena derived from an assumption that the number displayed on the calculator physically propagates through a transmission line, physically reflects off the ends of the transmission line or other discontinuities, and physically interferes with itself or other numbers like it. So that there is no further mistaking my position, I dispute the validity of these descriptions of the behavior of physical phenomena, and some of the predictions based upon them. I do not dispute P=V*I, but thanks for asking. The wave which propagates along a transmission line can produce energy at a rate proportional to E x H, but it is not E x H which propagates along the transmission line. E propagates in one plane, and H propagates in a plane a right angles to E. When we know the characteristics of E and H (or V and I) individually, we can predict what will occur when either encounters a discontinuity. But when we multiply to two together, the resulting magnitude no longer possesses the properties of either of the multiplicands, and so no accurate predictions about interactions with discontinuities can truly be derived without making assumptions. And as we've seen, given a nebulous laundry list of assumptions, some inaccurate predictions can be derived. Your 'Transformer' diagrams come as close as any I've seen to describing how things behave in an coaxial impedance matching arrangement. I hope you include them in your 3rd Edition. I have, by the way, found similar but less detailed drawings of thin film interfaces in two different physics textbooks. I think the key to understanding them is the superposition of multiple reflections. 73, Jim AC6XG |
Whatever floats your boat, Richard. If you need to think of power as an
'ability' that flows through an electrical pipe, then I think you should think of it that way. 73, Jim Richard Harrison wrote: Jim Kelley wrote: "---power does not flow or move, nor is it something that can be reflected." From the Random House American College Dictionary: Power is the ability to do or act. It is the time rate of transferring or transforming energy. It is work done or energy transferred per unit of time. The power to do or act can be moved from one location to another. A power house is an electrical generating station where some other form of energy is converted to electricity which is very flexible in application. From the power house, the power (ability to do or act) is transported by power transmission lines to the places it is used. Since the wavelength at 60 Hz is 5 million meters, (5000 km), power transmission lines aren`t long enough to produce standing waves which are caused by reflections. Radio-frequency transmission lines are often long enough to show the effects of reflections and the standing waves produced by those reflections. Power flows in r-f lines and it is reflected at impedance discontinuities accordimg to the most knowledgeable experts. F.E. Terman is my favorite. Best regards, Richard Harrison, KB5WZI |
On Wed, 03 Aug 2005 11:54:08 -0700, Jim Kelley
wrote: I have, by the way, found similar but less detailed drawings of thin film interfaces in two different physics textbooks. I think the key to understanding them is the superposition of multiple reflections. Hi Jim, Such coverage as you describe, in physics textbooks, are rudimentary discussions suitable for introductory purposes. They are not the end-all be-all nor final word on the matter. This is born out by exhausting work being pursued by many in academia and the industry to "completely cancel" reflections. They would not be so engaged in this work if a simple, quarterwave, thin layer optic performed this complete cancellation already. The fact of the matter is that by the mechanics so described in the text books, they guarantee no totality of cancellation. True, they offer a close hit, but this is not proof of totality. Close is good enough for nuclear hand grenades too. When the energy available in the first medium, at the second interface, cannot possibly reflect enough of it to the first interface; then no amount of superposition of ALL reflections (and this presumes that the second interface is fully reflecting for these succeeding multiples, an absurd notion in its own right) can exceed that available energy. Yes, this has all been said before, you've found it interesting but not compelling; and yet no one here has offered any way to boost the energy to completely cancel the reflection from the first interface. Under the circumstances already described, those reflection products (after assuming ALL the multiple reflections have been ushered out from behind the first interface to destructively interfere) contain: 1800 TIMES MORE POWER THAN THE SUN! which has been humorously relegated to zero. :-) Flowing, dribbling, puddling, or simply expressed in terms of candelas per square foot per fortnight, it all leads to the same conclusion: the cancellation is not total. Hence the subject line of The Extreme Failure of Poor Concepts in Discussing Thin Layer Reflections ********* for those who cannot cope with the topic ************* I have a D Cell battery whose capacity is 3 W-HR, and I roll it along the floor. Has power flowed? How much? (sorry if I offended anyone by asking for a quantitative answer) 73's Richard Clark, KB7QHC |
Richard Clark wrote: On Wed, 03 Aug 2005 11:54:08 -0700, Jim Kelley wrote: I have, by the way, found similar but less detailed drawings of thin film interfaces in two different physics textbooks. I think the key to understanding them is the superposition of multiple reflections. Hi Jim, Such coverage as you describe, in physics textbooks, are rudimentary discussions suitable for introductory purposes. They are not the end-all be-all nor final word on the matter. This is born out by exhausting work being pursued by many in academia and the industry to "completely cancel" reflections. They would not be so engaged in this work if a simple, quarterwave, thin layer optic performed this complete cancellation already. The fact of the matter is that by the mechanics so described in the text books, they guarantee no totality of cancellation. True, they offer a close hit, but this is not proof of totality. Close is good enough for nuclear hand grenades too. When the energy available in the first medium, at the second interface, cannot possibly reflect enough of it to the first interface; then no amount of superposition of ALL reflections (and this presumes that the second interface is fully reflecting for these succeeding multiples, an absurd notion in its own right) can exceed that available energy. Yes, this has all been said before, you've found it interesting but not compelling; and yet no one here has offered any way to boost the energy to completely cancel the reflection from the first interface. Under the circumstances already described, those reflection products (after assuming ALL the multiple reflections have been ushered out from behind the first interface to destructively interfere) contain: 1800 TIMES MORE POWER THAN THE SUN! which has been humorously relegated to zero. :-) Flowing, dribbling, puddling, or simply expressed in terms of candelas per square foot per fortnight, it all leads to the same conclusion: the cancellation is not total. Hence the subject line of The Extreme Failure of Poor Concepts in Discussing Thin Layer Reflections ********* for those who cannot cope with the topic ************* I have a D Cell battery whose capacity is 3 W-HR, and I roll it along the floor. Has power flowed? How much? (sorry if I offended anyone by asking for a quantitative answer) 73's Richard Clark, KB7QHC Hi Richard. The example you provided earlier is not any result of exhaustive research. It is not even an accurate thumbnail sketch of the phenomenon at the level of "rudimentary physics books". So I disagree with your assessment. (Perhaps you should consider having a look at the text you're characterizing first before you presume to characterize it.) But if by all that you mean to say that it's not possible to make a perfect anything, then I think that ordinarily goes without saying. So yes, you're right. There is no such thing as a lossless medium. But it is a rather simple matter to get a reasonably good match using this technique. I think you can assume that's about the degree of accuracy we're using for most of our discussions. 73, AC6XG PS I like your power flow analogy. :-) |
On Wed, 03 Aug 2005 13:30:47 -0700, Jim Kelley
wrote: Hi Richard. The example you provided earlier is not any result of exhaustive research. It is not even an accurate thumbnail sketch of the phenomenon at the level of "rudimentary physics books". Hi Jim, This is what I mean by no argument being put forth to dispute what has been offered. In fact every computation offered flows from the math offered by ANY academic text. I even name the math used, and then use it. In fact, I have lead the way by offering every cogent formula needed to discuss this matter. I see no dispute in the assignment of indices of reflection. I see no dispute in the computation of reflections. I see no dispute in the balance of energy at each interface. And I am speaking of quantitative results, not presumptions. The chain of causality is not very long, it exhibits very obvious contradictions to the notion of "totality," and the practical example is hardly from the sphere of the wildly imaginative. The example is further exhibited as a practical problem of current research. So I disagree with your assessment. OK, so you disagree, but that is not an argument, it is simply a statement of prejudice. (Perhaps you should consider having a look at the text you're characterizing first before you presume to characterize it.) and this is a characterization of its own. But if by all that you mean to say that it's not possible to make a perfect anything, then I think that ordinarily goes without saying. What I mean has been clearly stated. Adding qualifiers on my behalf goes outside of the discussion. So yes, you're right. I state nowhere that "perfect" is expected, nor do I impose that as a condition. Can we leave these speculations outside of the discussion? There is no such thing as a lossless medium. This is a non-sequitur injected for no apparent reason. Why so? But it is a rather simple matter to get a reasonably good match using this technique. You've gone to great lengths to extrapolate and postulate what I've said, and yet fail to commend me for having said just this any number of times. Why so? I think you can assume that's about the degree of accuracy we're using for most of our discussions. For "Total cancellation?" If you accept that, you've spent four years arguing for... what have you been arguing about? Have you allowed this slack you accept in our behalf for your own positions? However, I am used to the "debate" that proceeds along these lines where "Totality" has been proven, accepted and it leads to nonsensical theories like waves reflecting waves. 73's Richard Clark, KB7QHC |
Richard Clark, KB7QHC wrote:
"I have a D Cell battery whose capacity is 3 W-HR, and I roll it along the floor. Has power flowed?" Reminds me of a point made by Tom Whitaker, a two-handed blackboard scribe and celebrated E.E. Prof I had over 1/2 century ago. Tom wrote with one hand and erased with the other so he would have a clear space to write more.To drive home his definition of current, Tom spat on a piece of chalk and chunked it with vigor the length of the auditorium where it bounced harmlessly from the rear wall. What an arm! Some ball club sgould have signed him. Tom said: "That spit was charged and you`ve just seen an electric current! Your D-cell holds much charge and rolling the cell puts charge in motion, So, yes, power has flowed because you transferred the ability to do work from one site to another. Best regards, Richard Harrison, KB5WZI |
Richard Clark wrote:
Hi Jim, This is what I mean by no argument being put forth to dispute what has been offered. In fact every computation offered flows from the math offered by ANY academic text. I even name the math used, and then use it. In fact, I have lead the way by offering every cogent formula needed to discuss this matter. Well, to be blunt I believe you may perhaps be overestimating the significance of your contributions on this subject, Richard. I see no dispute in the assignment of indices of reflection. I see no dispute in the computation of reflections. I see no dispute in the balance of energy at each interface. And I am speaking of quantitative results, not presumptions. I've seen dispute of your numbers. Cecil had them right. Cecil is very good at getting the numbers right. I even agree with the solutions to his irradiance equations. He and I disagree only on certain details of the physical mechanism (though he seems to want to disagree with just about anything I have to say). But if by all that you mean to say that it's not possible to make a perfect anything, then I think that ordinarily goes without saying. There is no such thing as a lossless medium. This is a non-sequitur injected for no apparent reason. Why so? Start with a presumption that it is not a non sequitur and see where that leads. I've reassembled my original statement above for your review. I think you can assume that's about the degree of accuracy we're using for most of our discussions. For "Total cancellation?" If you accept that, you've spent four years arguing for... what have you been arguing about? Have you allowed this slack you accept in our behalf for your own positions? The relevance of the "non sequitur" stated above thereby makes itself apparent. There are several reasons why it is difficult to achieve total cancellation of reflected light at an optical surface. First - the obvious one. A quarter wave layer is only a quarter wavelength thick at one wavelength. Second - dielectric films can be lossy. Third - anti-reflection is only 100% effective at normal incidence. Fourth - it's next to impossible to make a film that has a refractive index which is the perfect geometric mean of the indices of the media at its boundaries. A thorough treatment of all the reflections at both boundaries, whereby all in-phase reflections in a given direction are summed, provides that absent the imperfections described above, total cancellation is indeed a fact. Another fact is that it's much easier to accomplish in a transmission line with monochromatic RF at HF. However, I am used to the "debate" that proceeds along these lines where "Totality" has been proven, accepted and it leads to nonsensical theories like waves reflecting waves. If I were to characterize most of the discussion I've had here, I would say most of it has been spent addressing misunderstandings related to the fundamental behavior of nature. 73, Jim AC6XG |
Jim Kelley wrote:
But some folks have argued descriptions of physical phenomena derived from an assumption that the number displayed on the calculator physically propagates through a transmission line, physically reflects off the ends of the transmission line or other discontinuities, and physically interferes with itself or other numbers like it. If you think that's what I said, you are suffering from delusions. *All* of my power components exist at a stationary point or plane. The two components associated with wave cancellation exist at the match *point*. "Reflected power" is the reflected energy flow per unit time measured at a point by a stationary directional wattmeter. "Forward power" is the forward energy flow per unit time measured at a point by a stationary directional wattmeter. Power components do not interfere. It is the E-fields and H-fields that do the interferring. However, given the interference of two coherent waves traveling in the same direction, the following power equation is valid. Ptotal = P1 + P2 + 2*sqrt(P1*P2)cos(phi) where phi is the phase angle between the two E-fields. The last term in that equation is well known as the "interference term". If cos(phi) is negative, the interference is destructive. If cos(phi) is positive, the interference is constructive. If an additional source of energy is not present at the interference point, the destructive interference must equal the constructive interference to satisfy the conservation of energy principle. Like I said before, the only disagreement that we have left is whether dt is zero or infinitessimally small. Your straw men are just straw men designed to mislead the uninitiated. Note that Richard Clark is NOT using the above power equation and is instead trying to superpose powers which is an invalid practice. That's why he's calculating the wrong values. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Cecil Moore wrote:
Jim Kelley wrote: But some folks have argued descriptions of physical phenomena derived from an assumption that the number displayed on the calculator physically propagates through a transmission line, physically reflects off the ends of the transmission line or other discontinuities, and physically interferes with itself or other numbers like it. If you think that's what I said, you are suffering from delusions. Perhaps I was deluded by all your arguing about it. :-) Power components do not interfere. Glad you finally agree. It is the E-fields and H-fields that do the interferring. Is there an echo in here? However, given the interference of two coherent waves traveling in the same direction, the following power equation is valid. Ptotal = P1 + P2 + 2*sqrt(P1*P2)cos(phi) where phi is the phase angle between the two E-fields. Right. That's simply because P is proportional to E^2. The last term in that equation is well known as the "interference term". Basically, yes. Two times the product of the two fields is the interference term. The product of two things which don't interfere is probably inappropriately referred to as an interference term. If cos(phi) is negative, the interference is destructive. If cos(phi) is positive, the interference is constructive. If an additional source of energy is not present at the interference point, the destructive interference must equal the constructive interference to satisfy the conservation of energy principle. .....and by virtue of the fact that 2*sqrt(P1*P2) = 2*sqrt(P1*P2). ;-) Like I said before, the only disagreement that we have left is whether dt is zero or infinitessimally small. As I recall, my disagreement with you was about your claim that "interference causes energy to reverse direction and go the other way". That's what it's always been about, Cecil. Do you still insist that's what happens? If not, then we're in agreement - unless you disagree, of course. Your straw men are just straw men designed to mislead the uninitiated. Actually the "straw men" seem to have brought you around substantially to the correct point of view. And I really don't think anyone who's been paying attention is misled about you, Cecil. :-) 73, ac6xg |
On Wed, 03 Aug 2005 15:51:03 -0700, Jim Kelley
wrote: This is what I mean by no argument being put forth to dispute what has been offered. In fact every computation offered flows from the math offered by ANY academic text. I even name the math used, and then use it. In fact, I have lead the way by offering every cogent formula needed to discuss this matter. Well, to be blunt I believe you may perhaps be overestimating the significance of your contributions on this subject, Richard. Hi Jim, Well, being blunt offers no more argument than previous statements of prejudice. And the point of the matter is I've observed no one here offer any math in advance of my presentation. If this is overestimating any significance, it certainly puts everything else in the shade. I see no dispute in the assignment of indices of reflection. I see no dispute in the computation of reflections. I see no dispute in the balance of energy at each interface. And I am speaking of quantitative results, not presumptions. I've seen dispute of your numbers. Cecil had them right. And yet and all, you have nothing at your fingertips: A dispute over indices of refraction? Nada. A dispute over reflection? Nada. A dispute over balanced energy equations? Nada. All rather first principles and central to the discussion. It takes very little effort to unscramble a half page of text if I've so messed it up; but I am content to see you are aligned with Cecil's argument and to watch where that leads. :-) It could lead to another fruitful 4 years of debate? 73's Richard Clark, KB7QHC |
Richard,
Try the link. See if it reminds you of anything. :-) jk http://www.montypythonpages.com/index1.htm Richard Clark wrote: On Wed, 03 Aug 2005 15:51:03 -0700, Jim Kelley wrote: This is what I mean by no argument being put forth to dispute what has been offered. In fact every computation offered flows from the math offered by ANY academic text. I even name the math used, and then use it. In fact, I have lead the way by offering every cogent formula needed to discuss this matter. Well, to be blunt I believe you may perhaps be overestimating the significance of your contributions on this subject, Richard. Hi Jim, Well, being blunt offers no more argument than previous statements of prejudice. And the point of the matter is I've observed no one here offer any math in advance of my presentation. If this is overestimating any significance, it certainly puts everything else in the shade. I see no dispute in the assignment of indices of reflection. I see no dispute in the computation of reflections. I see no dispute in the balance of energy at each interface. And I am speaking of quantitative results, not presumptions. I've seen dispute of your numbers. Cecil had them right. And yet and all, you have nothing at your fingertips: A dispute over indices of refraction? Nada. A dispute over reflection? Nada. A dispute over balanced energy equations? Nada. All rather first principles and central to the discussion. It takes very little effort to unscramble a half page of text if I've so messed it up; but I am content to see you are aligned with Cecil's argument and to watch where that leads. :-) It could lead to another fruitful 4 years of debate? 73's Richard Clark, KB7QHC |
Jim Kelley wrote:
Perhaps I was deluded by all your arguing about it. :-) I'm saying, "I agree" and you are saying, "No, you don't" so who's doing the arguing? Here's an example from a posting way back in 2004: ************************************************** *********************** Jim Kelley wrote: The crux of the phenomenological problem is that power does not flow or move, nor is it something that is reflected. But energy does flow and move and is something that can be reflected. ************************************************** ************************ In that posting, I am agreeing with you but your delusions make you assert to this very day that I was arguing with you. Power components do not interfere. Glad you finally agree. I have never said otherwise. I often identify the wave component by the power figure, but it is *only a name* used to identify an EM wave. When I say, "The 50 watt wave interferes with the 25 watt wave", I'm not saying that 50 watts interferes with 25 watts. It's the *waves* that interfere, not the watts! Why is that so hard for you to comprehend? Ptotal = P1 + P2 + 2*sqrt(P1*P2)cos(phi) where phi is the phase angle between the two E-fields. Right. That's simply because P is proportional to E^2. I'm glad you finally agree after arguing against it for years. (See, two can play your junevile game.) The last term in that equation is well known as the "interference term". Basically, yes. Two times the product of the two fields is the interference term. The interference is in the units of power, e.g. joules/sec. It is two times the square root of the product of the two powers associated with the two interferring waves. It is the result of superposition of two coherent EM waves. As I said before, it is the waves that interfere, NOT the powers. The product of two things which don't interfere is probably inappropriately referred to as an interference term. Your argument is with Hecht and other scientists, physicists, and engineers who use that convention, not just with me. You would have made a good lawyer since you seem to object to virtually everything. :-) Like I said before, the only disagreement that we have left is whether dt is zero or infinitessimally small. As I recall, my disagreement with you was about your claim that "interference causes energy to reverse direction and go the other way". That's what it's always been about, Cecil. Destructive interference in one direction in a transmission line results in constructive interference in the opposite direction. Anything else would violate the conservation of energy principle. Our argument is whether destructive interference has time to happen, i.e. how many calculus dt's can dance on the head of a pin. :-) Whether interference can cause energy to reverse direction or not depends upon whether dt equals zero as you imply, or whether dt equals an infinitessimally small amount of time as I say. That's what it's always been about, Jim. Do you still insist that's what happens? If not, then we're in agreement - unless you disagree, of course. If dt is an infinitessimally small amount of time, then that is exactly what happens. If dt equals zero, then it doesn't have time to happen. Your argument is that it doesn't have time to happen because "there is no before and after". (a quote from your email). I say there is a before, now, and after divided into infinitessimally small dt's of time and when added together, actually perform the function of representing the flow of time. So are you going to assert that time also doesn't flow? -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Richard Clark wrote:
When the energy available in the first medium, at the second interface, cannot possibly reflect enough of it to the first interface; then no amount of superposition of ALL reflections (and this presumes that the second interface is fully reflecting for these succeeding multiples, an absurd notion in its own right) can exceed that available energy. Yes, this has all been said before, you've found it interesting but not compelling; and yet no one here has offered any way to boost the energy to completely cancel the reflection from the first interface. I have multiple times, Richard. When a 111.1mW wave interferes with an 87.78mW wave, the result is *NOT* a 23.32mW wave. It's the waves that interfere, not the power. 111.1mW - 87.78mW = 23.32mW is superposition of powers and is invalid! Instead of superposing powers, the equation you need to use is the power interference equation: Pref1 = P1 + P2 + 2*sqrt(P1*P2)cos(180) Pref1 = 111.1mW + 87.78mW + 2*sqrt(111.1*87.78)(-1) Pref1 = 198.88mW - 197.51mW = 1.37mW Thus after only one internal reflection cycle, the reflected power, Pref1, is reduced to 1.37mW, not to 23.32mW as you have asserted. If you will use a transmission line example and deal with voltages, you will be able to diagnose your mistake. Voltages interfere, watts don't. Most RF engineers simply do not understand how to deal with powers associated with component wave interference. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Richard Clark wrote:
I see no dispute in the balance of energy at each interface. Conclusion: You have to be blind. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
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