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On Mar 26, 1:37*pm, Cecil Moore wrote:
Keith Dysart wrote: Now if the 200 W from the wave from source 1 and the 50 W from the wave from source 2 represent actual energy flows, then the "interference energy" must also be an actual energy flow to satisfy conservation of energy. One other observation: Although the interference model will work for a lumped circuit example, there is no reason to use it as it complicates the computations and adds nothing to the solution. The wave reflection model also works for circuits but there is simply no good reason to use it for lumped circuit analysis. Except when it can be called into service to disprove some aspects of *your* "wave reflection model". Where interference becomes a useful tool is when it happens away from any compensating source. An analysis of the interference of two EM light waves in free space far removed from any source leaves us with two constant sources of energy, the total energy of which has to go somewhere. The following two web pages tell us exactly where the energy goes. http://www.mellesgriot.com/products/optics/oc_2_1.htm http://micro.magnet.fsu.edu/primer/j...interference/w... It is unfortunate that they did not expect someone to use their website to try to understand the behavior of transmission lines, or they might have taken more care to explain what is happening at the sub-wavelength level. Your theory seems to require that the EM waves must know beforehand whether to carry energy or not from a star light years away. You apparently have invented a rather curious "smart wave theory". That would be nice, but no, not required. Though it is easy to see how one might be misguided into thinking so. The question is, can you set aside the mis-guiding influences long enough to learn about the alternative explanations? The question is: How did those two interfering waves from Alpha Centauri know whether to arrive at the planet Earth ten years later carrying ExH energy or not carrying ExH energy? It is a question, but only seems relevent if *your* model is incorrect. ...Keith |
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On Mar 26, 2:53*pm, Cecil Moore wrote:
Keith Dysart wrote: Let us build a slightly better example that complies with your "NOT =" expression above. Your constant voltage sources are NOT a better example and not even a good example. To confront the subject being discussed, you should use constant power sources. Well, if that is all it takes to stop you, here is a variation that should satisfy. It aligns well with your example of Fig 1-1...... Let us build a slightly better example that complies with your "NOT =" expression above. 50 ohms 50 ohms +------/\/\/\----------------+---/\/\/\---+ | | | | \ | Vs1(t) = 282.8cos(wt) Rload / Vs2(t) = 141.4cos(wt) | = 200 Vrms 50 ohms \ | = 100 Vrms | / | | | | +----------------------------+------------+ Using superposition the contribution from source 1 is Vload.s1 = 100 Vrms Iload.s1 = 2 Arms and from source 2 is Vload.s2 = 50 Vrms Iload.s2 = 1 Arms combining Vload = 150 Vrms Iload = 3 Arms From Pload = Vload * Iload = 150 * 3 = 450 Waverage As can be seen, this example satisfies your requirement for interference: [V1(t)^2 + V2(t)^2] NOT= [V1(t) + V2(t)]^2 Computing the imputed powers for the waves from each source we have Pload.s1 = 100 * 2 = 200 Waverage Pload.s2 = 50 * 1 = 50 Waverage To obtain the power in the load from these imputed powers we need to use Pload = Pload.s1 + Pload.s2 + Pload.correction 450 = 200 + 50 + Pload.correction 200 = Pload.correction From previous analysis Pcorrection = 2 * sqrt(P1 * P2)cos(theta) (the cos(theta) term is appropriate here because these are average powers being used) Pcorrection = 2 * sqrt(10000) * 1 = 200 as required from above. So according to your energy analsysis, the power in the load comes from the wave from source 1 = 200 W the wave from source 2 = 50 W "interference energy" = 200 W for a total of 450 W as required. Now if the 200 W from the wave from source 1 and the 50 W from the wave from source 2 represent actual energy flows, then the "interference energy" must also be an actual energy flow to satisfy conservation of energy. What element provides the energy for this "interference energy" flow? In other posts, you have suggested that this would be a constructive interference energy and that there would be an equal destructive interference energy to provide it. If you still claim this, where is this destructive interference happening? ...Keith |
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Keith Dysart wrote:
Or perhaps the element you have identified does not have the appropriate energy flow function? (It doesn't.) Please prove your assertion. This requires that the sum of the flows out of the elements providing energy equals the sum of the flows into the elements receiving the energy. True for energy. Not true for power. And we are still waiting for the energy flow function for the element that you claim is doing the storing of the energy. If you cannot understand the reference I gave you, I don't know what to tell you. Does it detect energy? Are you sure? Or is it voltage that it detects? Or current? Please provide proof that voltage or current can exist without energy. -- 73, Cecil http://www.w5dxp.com |
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Keith Dysart wrote:
The question is, can you set aside the mis-guiding influences long enough to learn about the alternative explanations? Sorry, I'm not interested in those religious concepts. -- 73, Cecil http://www.w5dxp.com |
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Keith Dysart wrote:
In other posts, you have suggested that this would be a constructive interference energy and that there would be an equal destructive interference energy to provide it. If you still claim this, where is this destructive interference happening? I have said a source can match any destructive interference by supplying less power and match any constructive interference by supplying more power. If you have to falsify what I have said to try to win the argument, you have already lost. Since you have ample sources available in your example, my assertion about interference far removed from any source doesn't apply - but you know that. -- 73, Cecil http://www.w5dxp.com |
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Keith Dysart wrote:
Cecil Moore wrote: In fact, the thing you need to do is forget the transmission line and deal with light waves encountering boundaries with different indexes of refraction. The problem is identical, but dealing with light out in the open prohibits you from pushing your mashed-potatoes energy religion. No. Light, in a 3 dimensional space and at such high frequency makes the math and measurements so complicated that it is extremely difficult to follow the energy. Now how did I know that you would refuse to expose your strange concepts to the light of day? -- 73, Cecil http://www.w5dxp.com |
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On Sun, 09 Mar 2008 21:33:41 -0400, Chuck
wrote: On Sun, 9 Mar 2008 15:07:26 -0700 (PDT), K7ITM wrote: snip Note that, as far as I've been able to determine, Michelson did not have a coherent light source to shine into his interferometer, but still he saw interference patterns. Perhaps he had invented lasers snip It is said he used sodium vapor gas light (~589 nm). Coherent enough. Monochromatic is not the same as coherent or in phase such as a laser. Chuck ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-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 =---- Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com |
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Cecil Moore wrote:
Roger Sparks wrote: You need to take a look at the spreadsheets. Roger, in a nutshell, what is the bottom line? The bottom line in a nutshell? I'll try. First, I added a note to both spreadsheets indicating that zero degrees is CURRENT zero degrees. This because the source turns out to be reactive, with current peak 45 degrees from voltage peak. http://www.fairpoint.net/~rsparks/Sm...Reflection.pdf The spreadsheet addresses the following issues: Does the traveling wave carry power? Yes. The spreadsheet was built assuming that power is carried by traveling waves. Because the resulting wave form and powers seem correct, the underlaying assumption seems correct. Is power conserved on the transmission line, meaning, can the energy contained in power be conserved and located over time on the transmission line? Yes, the spreadsheet was built assuming that power could be conserved and traced over time so the underlaying assumption seems correct. Does interference occur in this example? The spreadsheet was built assuming that voltage and currents from superpose in a manner consistent with constructive and destructive interference, so the underlaying assumption seems correct. Is power stored in the reactive component for release in later in the cycle or during the next half cycle? Yes, power is stored on the transmission line during the time it takes for power to enter the line, travel to the end and return. The time of wave travel on the transmission line is related to the value of the reactive component. Does the direction of wave travel affect the measurement of voltage and the application of power to a device? Yes. A wave loses energy (and therefore voltage) as it travels through a resistance. As a result, power from the prime source is ALWAYS applied across the sum of the resistance from the resistor AND transmission line. The spreadsheet was built using this assumption and seems correct. (At times during the cycle, the forward and reflected waves oppose, resulting in very little current through the resistor. During those times, the power applied to the transmission line is much HIGHER because the reflected wave reflects from the load and source, and merges/adds to the forward wave from the source.) Is the power interference equation Ptot = P1 + P2 + 2*SQRT(P1*P2)cos(theta) valid? The equation was not reviewed on this spreadsheet. The bottom line, but maybe not in a nutshell. 73, Roger, W7WKB |
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Roger wrote:
Note that, as far as I've been able to determine, Michelson did not have a coherent light source to shine into his interferometer, but still he saw interference patterns. Perhaps he had invented lasers It is said he used sodium vapor gas light (~589 nm). Coherent enough. Monochromatic is not the same as coherent or in phase such as a laser. Just a slight addition here. Before lasers, the way to get a coherent light source was to bottle-up a high-intensity, monochromatic source, such as the aforementioned sodium- vapor light, in a reflective cavity with a very small pinhole in its side. As the photons dribble out through the pinhole, they are forced into a somewhat phase-coherent wave train. This source was used in optical processors for synthetic-aperture radar imagery back in the 50's.... Jim, K7JEB |
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Roger Sparks wrote:
The bottom line in a nutshell? I'll try. Thanks Roger, good stuff and much appreciated. My digesting of your spread sheets is about to be interrupted by surgery. During those times, the power applied to the transmission line is much HIGHER because the reflected wave reflects from the load and source, and merges/adds to the forward wave from the source.) May I suggest that you use the word "redistributed" instead of "reflected" as does the FSU web page at: http://micro.magnet.fsu.edu/primer/j...ons/index.html For the purposes of this discussion, I would suggest that the word "reflection" be reserved for something that happens to a single wave. When two waves are superposed, energy can be redistributed but technically it is not an ordinary reflection. I once used the word "reflection" to describe both phenomena and it confused people. Now I am careful to call the reversal of energy flow due to superposition a "redistribution" instead of a "reflection". For instance, the multi-colored patterns seen when a thin film of oil is on top of a puddle of water is not an ordinary reflection but a combination of multiple reflections and interference. In addition, the reflection coefficient seen by the reflected wave in our examples is 0.0 since the source impedance equals the characteristic impedance of the transmission line. There are no ordinary reflections when the reflection coefficient is zero. -- 73, Cecil http://www.w5dxp.com |
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On Mar 26, 9:35*pm, Cecil Moore wrote:
Keith Dysart wrote: Or perhaps the element you have identified does not have the appropriate energy flow function? (It doesn't.) Please prove your assertion. So you are having difficulty doing the math to justify your hypothesis. This requires that the sum of the flows out of the elements providing energy equals the sum of the flows into the elements receiving the energy. True for energy. Not true for power. Ummmmm. Conservation of energy requires that the total quantity of energy in the system not change. This requires that the sum of the changes of the quantity of energy in each element be zero. A change in energy quantity is a flow. The energy flows must sum to zero. Energy flow is power. The powers must sum to 0 to satisfy conservation of energy. And we are still waiting for the energy flow function for the element that you claim is doing the storing of the energy. If you cannot understand the reference I gave you, I don't know what to tell you. You could simply do the derivation for an example that demonstrates your hypothesis. Does it detect energy? Are you sure? Or is it voltage that it detects? Or current? Please provide proof that voltage or current can exist without energy. I realize now that you were probably thinking of a TDR that sent a pulse (I was thinking of one that sent a step). My assertion is that when Ptotal = Pfor - Pref the idea that Pfor and Pref describe actual energy flows is very dubious. Ptotal always describes an energy flow. When Pfor is 0, then Pref is equal to Ptotal and since Ptotal is always describing an energy flow, Pref does in this case as well. Similarly when Pref is 0. ------- And now, since you are having trouble computing the energy flows into the various elements here they are again, for the circuit in the example of Fig 1-1, 100 Vrms sinusoidal source, 50 ohm source resistor, 45 degrees of 50 ohm line, 12.5 ohm load, after the reflection returns... The power flow into the line is Pg(t) = 32 + 68cos(2wt) and along with Ps(t) = 100 + 116.6190379cos(2wt-30.96375653) Prs(t) = 68 + 68cos(2wt-61.92751306) energy is nicely conserved because Ps(t) = Prs(t) + Pg(t) The load presented by the line has a resistive and a reactive component, so we can separate the power into two parts Pg.resis(t) = 32 + 32cos(2wt-61.92751306) Pg.react(t) = 0 + 60cos(2wt+28.07248694) which, for confirmation, nicely sums to Pg(t) above. Now as I recall, your claim was that the total power dissipated in the source resistor would be the power dissipated before the reflection returned plus the power imputed to be in the reflected wave plus the power stored in and returned from some other element in the circuit. Prs(t) = 50 + 50cos(2wt) + Pr.g(t) + Pstorage = 50 + 50cos(2wt) + 18 - 18cos(2wt) + Pstorage Pstorage = 68 + 68cos(2wt-61.92751306) - 50 - 50cos(2wt) - 18 + 18cos(2wt) = 0 + 36cos(2wt-90) which is not the power function of the reactive component of the line input impedance, Pg.reac(t), computed above. So the energy is not being stored in the reactive component of the line input impedance. ...Keith |
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On Mar 26, 9:51*pm, Cecil Moore wrote:
Keith Dysart wrote: In other posts, you have suggested that this would be a constructive interference energy and that there would be an equal destructive interference energy to provide it. If you still claim this, where is this destructive interference happening? I have said a source can match any destructive interference by supplying less power and match any constructive interference by supplying more power. If you have to falsify what I have said to try to win the argument, you have already lost. Since you have ample sources available in your example, my assertion about interference far removed from any source doesn't apply - but you know that. I had not realized that you had these alternate sources for the interference energies, not having seen that in your papers. But it is one way to sidestep the issue; different rules for the expectations of superposition and interference in different scenarios. I am surprised then, for the example of Fig 1-1 with 12.5 ohms, that you don't just say "There is a source nearby, that *must* be where the unaccounted energy comes from", and leave it at that. ...Keith |
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On Thu, 27 Mar 2008 11:49:03 GMT
Cecil Moore wrote: Roger Sparks wrote: The bottom line in a nutshell? I'll try. Thanks Roger, good stuff and much appreciated. My digesting of your spread sheets is about to be interrupted by surgery. Thanks for the kind words. Sorry to hear about your surgery. I hope it goes well and you have a quick recovery. During those times, the power applied to the transmission line is much HIGHER because the reflected wave reflects from the load and source, and merges/adds to the forward wave from the source.) May I suggest that you use the word "redistributed" instead of "reflected" as does the FSU web page at: http://micro.magnet.fsu.edu/primer/j...ons/index.html Clip I think "redistributed" would be the word if the discontinuity included a resistance. "Reflection" is the historical word for wave reversal and implies a "mirror image", which is not the same as the forward image. I hope the surgery does not take you away from the discussion for long. -- 73, Roger, W7WKB |
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Keith Dysart wrote:
So you are having difficulty doing the math to justify your hypothesis. Actually no, the math is not difficult. I'm pre- occupied with something else and think it's just time to agree with Hecht that instantaneous power is "of limited utility". Have you taken a look at Roger's spreadsheets? Conservation of energy requires that the total quantity of energy in the system not change. :-) Isn't the whole purpose of a transmitting antenna to radiate energy away from the antenna system? And that radiation continues to be "lost" from the system space for some time after the source power is removed? Wouldn't you have to define the "system" as the entire universe for your statement to be true? The powers must sum to 0 to satisfy conservation of energy. That may be true, but there's still no conservation of instantaneous power principle. A hot resistor continues to radiate heat long after any power source is removed. You could simply do the derivation for an example that demonstrates your hypothesis. Already done on my web page. My only actual hypothesis concerns average power. I've wasted too much time bantering about something that Hecht says is "of limited utility". the idea that Pfor and Pref describe actual energy flows is very dubious. Again, look yourself in the mirror and tell yourself that what you are seeing contains no energy. The theory that some EM waves contain energy and some do not is not new to you. Dr. Best was the first to theorize that canceled waves continue to propagate forever devoid of energy. Someone else asserted that canceled waves never contained any energy to start with. I strongly suspect that what you are seeing in the mirror are the waves that didn't cancel and that do contain energy. :-) So the energy is not being stored in the reactive component of the line input impedance. Assuming you have not made an error, so what? Energy stored in the reactance is only one of the possibilities that I listed earlier. As I said in an earlier posting which you declared a non-sequitor (sic), one or more of the following is true: 1. The source adjusts to the energy requirements. 2. The reactance stores and delivers energy. 3. Wave energy is redistributed during superposition. 4. Something I haven't thought of. The ExH reflected wave energy exists and cannot be destroyed. It goes somewhere and its average value is dissipated in the source resistor in my special case example. You are attempting to destroy the reflected wave energy using words and math presumably knowing all along that reflected wave energy cannot be destroyed. -- 73, Cecil http://www.w5dxp.com |
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Keith Dysart wrote:
I had not realized that you had these alternate sources for the interference energies, not having seen that in your papers. I only posted it three times here and you chose to ignore all of those postings. I have published only one paper with three more to go. The special case Part 1 contains zero average interference so there is no alternate source for average interference and indeed, none is needed for Part 1. But it is one way to sidestep the issue; different rules for the expectations of superposition and interference in different scenarios. That's why I have four parts only one of which has been published. The rules are not different but the conditions within the examples are different. Part 2 will be an example with the condition of average destructive interference existing at the source resistor. Although there are no ordinary reflections because the reflection coefficient is 0.0, there will exist something that looks a lot like a reflection caused by superposition/interference. The FSU web page calls it a "redistribution", not a "reflection". I am satisfied with FSU's word "redistribution" for the results of coherent wave interaction. I am surprised then, for the example of Fig 1-1 with 12.5 ohms, that you don't just say "There is a source nearby, that *must* be where the unaccounted energy comes from", and leave it at that. Since my special case example contains zero average interference, the average power output of the source is constant and unaffected by zero interference. There is zero average energy unaccounted for. Part 2 will illustrate the source adjusting its power output to compensate for destructive interference. -- 73, Cecil http://www.w5dxp.com |
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Roger Sparks wrote:
I think "redistributed" would be the word if the discontinuity included a resistance. "Reflection" is the historical word for wave reversal and implies a "mirror image", which is not the same as the forward image. What I am suggesting is that "redistribution" be used instead of "reflection" for cases where there exists no discontinuity. If the source resistor matches the Z0 of the feedline, there is no discontinuity and therefore no conventional reflection, yet there are cases where reflected energy is redistributed back toward the load. That reversal appears to be a reflection but is actually the result of superposition along with destructive interference between *two* waves. That is what causes the disparity between the physical reflection coefficient, (Z1-Z2)/(Z1+Z2), and the virtual reflection coefficient, SQRT(Pref/Pfor). I hope the surgery does not take you away from the discussion for long. At the least, I should still have one good eye left. ;-) -- 73, Cecil http://www.w5dxp.com |
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Cecil Moore wrote:
What I am suggesting is that "redistribution" be used instead of "reflection" for cases where there exists no discontinuity. This is sad. But I suppose that if you are going to invent new science you might as well invent new terminology as well. 8-) Yes, I know that the now-famous FSU web page uses "redistribution". Did you happen to notice that the page was created by a lab tech and a Java programmer? Do you suppose Hecht, Born and Wolf, and all of the other acknowledged experts would support dumping "reflection"? 73, Gene W4SZ |
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Gene Fuller wrote:
Yes, I know that the now-famous FSU web page uses "redistribution". Do you suppose Hecht, Born and Wolf, and all of the other acknowledged experts would support dumping "reflection"? I would guess the answer is "yes" when the physical reflection coefficient is zero - in order to avoid a logical contradiction. How does a "reflection" occur when the physical reflection coefficient is zero, in violation of the wave reflection model? Why is there often a difference between the physical reflection coefficient and the virtual reflection coefficient? Which one is wrong? The convention that I have adopted is that the word "reflection" is reserved for single wave events. For multiple wave events where interference exists, something besides a simple "reflection" takes place. The intricate color patterns on the surface of a thin film of oil floating on a puddle of water are not simple reflections but instead an interaction of multiple reflected waves. The resulting image bears absolutely no resemblance to the incident image. Following the FSU web page usage, the word "redistribution" is used for multiple wave interaction events like wave cancellation. (The words we choose to use to describe the phenomena have zero effect on the phenomena.) "A rose by any other name would smell as sweet." -- 73, Cecil http://www.w5dxp.com |
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Gene Fuller wrote:
Did you happen to notice that the page was created by a lab tech and a Java programmer? Gene, if a tech asserts a fact and an expert asserts a falsehood, who are you going to choose to believe? -- 73, Cecil http://www.w5dxp.com |
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On Mar 27, 6:44*pm, Cecil Moore wrote:
Gene Fuller wrote: Did you happen to notice that the page was created by a lab tech and a Java programmer? Gene, if a tech asserts a fact and an expert asserts a falsehood, who are you going to choose to believe? The simulator at that web site does seem to have its issues. Ask it to simulate 700 nm + 680 nm at the same amplitude and see if the result represents reality. ...Keith PS. The result should look like a 689.8 nm sine wave of continuously varying amplitude. |
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Keith Dysart wrote:
The simulator at that web site does seem to have its issues. Ask it to simulate 700 nm + 680 nm at the same amplitude and see if the result represents reality. The duration of each calculation appears to be about one second and then a reboot. -- 73, Cecil http://www.w5dxp.com |
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On Mar 27, 2:06 am, Roger Sparks wrote:
Cecil Moore wrote: Roger Sparks wrote: You need to take a look at the spreadsheets. Roger, in a nutshell, what is the bottom line? The bottom line in a nutshell? I'll try. First, I added a note to both spreadsheets indicating that zero degrees is CURRENT zero degrees. This because the source turns out to be reactive, with current peak 45 degrees from voltage peak. http://www.fairpoint.net/~rsparks/Sm...Reflection.pdf I was not able to discern the derivation of the various equations though the data in the columns looked somewhat reasonable. Were the equation really based on the opening paragraph statement of 100 Vrms, or is it scaled to a different source voltage. The sin functions have an amplituted of 100, which suggests a source of 200 volts or Vrms of 141.4 volts. The spreadsheet addresses the following issues: Does the traveling wave carry power? Yes. The spreadsheet was built assuming that power is carried by traveling waves. Because the resulting wave form and powers seem correct, the underlaying assumption seems correct. It was not obvious which columns were used to draw this correlation. However, even if this experiment is consistent with the hypothesis it only takes one experiment which is not to disprove the hypothesis. Is power conserved on the transmission line, meaning, can the energy contained in power be conserved and located over time on the transmission line? Yes, the spreadsheet was built assuming that power could be conserved and traced over time so the underlaying assumption seems correct. Does interference occur in this example? The spreadsheet was built assuming that voltage and currents from superpose in a manner consistent with constructive and destructive interference, so the underlaying assumption seems correct. Is power stored in the reactive component for release in later in the cycle or during the next half cycle? Yes, power is stored on the transmission line during the time it takes for power to enter the line, travel to the end and return. The time of wave travel on the transmission line is related to the value of the reactive component. Does the direction of wave travel affect the measurement of voltage and the application of power to a device? Yes. A wave loses energy (and therefore voltage) as it travels through a resistance. As a result, power from the prime source is ALWAYS applied across the sum of the resistance from the resistor AND transmission line. I am not sure that I would describe this as the wave losing energy, but rather as the voltage dividing between the two impedances. If the source resistance was replaced by another transmission, which could easily be set to provide a 50 ohm impedance, would you still describe it as the wave losing energy? The spreadsheet was built using this assumption and seems correct. (At times during the cycle, the forward and reflected waves oppose, resulting in very little current through the resistor. During those times, the power applied to the transmission line is much HIGHER because the reflected wave reflects from the load and source, and merges/adds to the forward wave from the source.) I am not convinced. When there is very little current through the resistor, there is also very little current into the transmission line. This suggests to me that the power applied to the transmission line is low. ....Keith |
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On Mar 27, 11:10 am, Cecil Moore wrote:
Keith Dysart wrote: So you are having difficulty doing the math to justify your hypothesis. Actually no, the math is not difficult. I'm pre- occupied with something else and think it's just time to agree with Hecht that instantaneous power is "of limited utility". Have you taken a look at Roger's spreadsheets? Yes. Conservation of energy requires that the total quantity of energy in the system not change. :-) Isn't the whole purpose of a transmitting antenna to radiate energy away from the antenna system? And that radiation continues to be "lost" from the system space for some time after the source power is removed? Wouldn't you have to define the "system" as the entire universe for your statement to be true? Sort of, but there is an easy work-around. Since we are not particularly interested in what happens to the energy going to the source resistor, for example, we define the boundary of the system to pass through the resistor and simply account for the energy as a flow out of the system. And we do the same for the source since we are not particularly interested in where the energy for the source comes from; we just account for it as a flow into the system. And lastly, we don't really care where the energy on the line goes to or comes from, so we just account for it as a flow out of the system. You may have noticed that we have removed all the components from the system, it is a null system, and all we are doing is accounting for the flows into and out of the system. Hence Ps(t) = Prs(t) + Pg(t) The powers must sum to 0 to satisfy conservation of energy. That may be true, but there's still no conservation of instantaneous power principle. To conserve energy however, i.e. to have no energy accumulate in the null system described above, the flows must balance at all times, that is, instantaneously. A hot resistor continues to radiate heat long after any power source is removed. If you want to be that complicated you can; energy is delivered instantaneously to the resistor according to Vr*Ir (or equivalently, V**2/R), stored in the resistor as heat and dissipated to the environment later. But for our purposes, we can stop that analysis at the point where the energy enters the resistor and use Vr(t) * Ir(t) to compute the instantaneous flow into the resistor. You could simply do the derivation for an example that demonstrates your hypothesis. Already done on my web page. My only actual hypothesis concerns average power. I've wasted too much time bantering about something that Hecht says is "of limited utility". Unfortunately for your hypothesis, average power is insufficient to account for energy which might be in the reflected wave. An average power analysis agrees with your hypothesis, while a more detailed instaneous analysis disproves it. the idea that Pfor and Pref describe actual energy flows is very dubious. Again, look yourself in the mirror and tell yourself that what you are seeing contains no energy. The theory that some EM waves contain energy and some do not is not new to you. Dr. Best was the first to theorize that canceled waves continue to propagate forever devoid of energy. Someone else asserted that canceled waves never contained any energy to start with. I strongly suspect that what you are seeing in the mirror are the waves that didn't cancel and that do contain energy. :-) If it was just a 'suspicion' you could probably let go of the idea long enough to learn what is really happening and why it is not inconsistent with the idea that reflected wave energy is a dubious concept. So the energy is not being stored in the reactive component of the line input impedance. Assuming you have not made an error, You *have* found it hard to the do the math; otherwise, you could detect an error, if there was one. so what? Energy stored in the reactance is only one of the possibilities that I listed earlier. As I said in an earlier posting which you declared a non-sequitor (sic), one or more of the following is true: 1. The source adjusts to the energy requirements. 2. The reactance stores and delivers energy. 3. Wave energy is redistributed during superposition. 4. Something I haven't thought of. Your explanation is not complete until you can identify the element that stores and returns the energy and its energy transfer function. The ExH reflected wave energy exists and cannot be destroyed. It goes somewhere and its average value is dissipated in the source resistor in my special case example. Or not, as has been shown with the detailed analysis. You are attempting to destroy the reflected wave energy using words and math presumably knowing all along that reflected wave energy cannot be destroyed. Energy can not be destroyed. This leads inexorably to the conclusion that the reflected wave does not necessarily contain energy. ....Keith |
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On Mar 27, 11:37 am, Cecil Moore wrote:
Keith Dysart wrote: I had not realized that you had these alternate sources for the interference energies, not having seen that in your papers. I only posted it three times here and you chose to ignore all of those postings. I have published only one paper with three more to go. The special case Part 1 contains zero average interference so there is no alternate source for average interference and indeed, none is needed for Part 1. But it is one way to sidestep the issue; different rules for the expectations of superposition and interference in different scenarios. That's why I have four parts only one of which has been published. The rules are not different but the conditions within the examples are different. Part 2 will be an example with the condition of average destructive interference existing at the source resistor. Although there are no ordinary reflections because the reflection coefficient is 0.0, there will exist something that looks a lot like a reflection caused by superposition/interference. The FSU web page calls it a "redistribution", not a "reflection". I am satisfied with FSU's word "redistribution" for the results of coherent wave interaction. I am surprised then, for the example of Fig 1-1 with 12.5 ohms, that you don't just say "There is a source nearby, that *must* be where the unaccounted energy comes from", and leave it at that. Since my special case example contains zero average interference, the average power output of the source is constant and unaffected by zero interference. There is zero average energy unaccounted for. Part 2 will illustrate the source adjusting its power output to compensate for destructive interference. Perhaps you should complete part one so that it fully accounts for the energy flows before progressing to writing part two. Average is not a full accounting. ....Keith |
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On Sat, 29 Mar 2008 12:45:48 -0700 (PDT)
Keith Dysart wrote: On Mar 27, 2:06 am, Roger Sparks wrote: Cecil Moore wrote: Roger Sparks wrote: You need to take a look at the spreadsheets. Roger, in a nutshell, what is the bottom line? The bottom line in a nutshell? I'll try. First, I added a note to both spreadsheets indicating that zero degrees is CURRENT zero degrees. This because the source turns out to be reactive, with current peak 45 degrees from voltage peak. http://www.fairpoint.net/~rsparks/Sm...Reflection.pdf I was not able to discern the derivation of the various equations though the data in the columns looked somewhat reasonable. Were the equation really based on the opening paragraph statement of 100 Vrms, or is it scaled to a different source voltage. The sin functions have an amplituted of 100, which suggests a source of 200 volts or Vrms of 141.4 volts. I simplified and changed the phase for the equation in column C from '100sin(wt-90) + 100sin(wt-180)' to '100sin(wt+90) + 100sin(-wt)' so that the total voltage in column D better matches with the voltages from my formula in column G. The equation for column B is just the sine wave for the base wave, showing the voltage resulting to the source resistor from the peak current. The equation in column C is the same (from current) but recognizes that current from the reflected wave will cancel the current from the forward wave coming through Rs. The two waves are traveling in opposite directions so one angle must be labeled with a negative sign so that it will rotate in the opposite direction. In column C, the first term is the reflected wave and the second term is the base wave. My formula, displayed in column G, uses the applied voltage of 141.4 volts. I thought it would be easier to see how the spreadsheet was built using current to find the voltages. You can see how the results of column D match well with those from column G. The spreadsheet addresses the following issues: Does the traveling wave carry power? Yes. The spreadsheet was built assuming that power is carried by traveling waves. Because the resulting wave form and powers seem correct, the underlaying assumption seems correct. It was not obvious which columns were used to draw this correlation. Column E and column F display power. Column F recognizes that if 100 watts is applied continueously (on the average) over an entire 360 degree cycle, the final power applied over time would be 360 * 100 = 36000 watt-degrees. Part of the power comes from the reflection, part comes directly. Obviously, interference is very much at work in this example. However, even if this experiment is consistent with the hypothesis it only takes one experiment which is not to disprove the hypothesis. True! Is power conserved on the transmission line, meaning, can the energy contained in power be conserved and located over time on the transmission line? Yes, the spreadsheet was built assuming that power could be conserved and traced over time so the underlaying assumption seems correct. Does interference occur in this example? The spreadsheet was built assuming that voltage and currents from superpose in a manner consistent with constructive and destructive interference, so the underlaying assumption seems correct. Is power stored in the reactive component for release in later in the cycle or during the next half cycle? Yes, power is stored on the transmission line during the time it takes for power to enter the line, travel to the end and return. The time of wave travel on the transmission line is related to the value of the reactive component. Does the direction of wave travel affect the measurement of voltage and the application of power to a device? Yes. A wave loses energy (and therefore voltage) as it travels through a resistance. As a result, power from the prime source is ALWAYS applied across the sum of the resistance from the resistor AND transmission line. I am not sure that I would describe this as the wave losing energy, but rather as the voltage dividing between the two impedances. If the source resistance was replaced by another transmission, which could easily be set to provide a 50 ohm impedance, would you still describe it as the wave losing energy? It should be OK to think of the voltage dividing between two impedances. The important thing is to consider how the reflected voltage sums with the forward voltage where it is measured. Because the two waves are traveling in opposite directions, the measured voltage is not the voltage applied to either Rs or the transmission line. This is why columns B and C must be added to find the total voltage across Rs. The spreadsheet was built using this assumption and seems correct. (At times during the cycle, the forward and reflected waves oppose, resulting in very little current through the resistor. During those times, the power applied to the transmission line is much HIGHER because the reflected wave reflects from the load and source, and merges/adds to the forward wave from the source.) I am not convinced. When there is very little current through the resistor, there is also very little current into the transmission line. This suggests to me that the power applied to the transmission line is low. I don't follow you here. Right, power into the transmission line is low when the current in is low, and it is high when the current is high. It is clear that peak current and peak voltage do not occur at the same time except when measured across the resistor in column D. ...Keith This is just one example, but it seems like the power is accounted for here. We need another example where power can NOT be accounted for. -- 73, Roger, W7WKB |
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On Mar 29, 7:18 pm, Roger Sparks wrote:
On Sat, 29 Mar 2008 12:45:48 -0700 (PDT) Keith Dysart wrote: On Mar 27, 2:06 am, Roger Sparks wrote: Cecil Moore wrote: Roger Sparks wrote: You need to take a look at the spreadsheets. Roger, in a nutshell, what is the bottom line? The bottom line in a nutshell? I'll try. First, I added a note to both spreadsheets indicating that zero degrees is CURRENT zero degrees. This because the source turns out to be reactive, with current peak 45 degrees from voltage peak. http://www.fairpoint.net/~rsparks/Sm...Reflection.pdf I was not able to discern the derivation of the various equations though the data in the columns looked somewhat reasonable. Were the equation really based on the opening paragraph statement of 100 Vrms, or is it scaled to a different source voltage. The sin functions have an amplituted of 100, which suggests a source of 200 volts or Vrms of 141.4 volts. I simplified and changed the phase for the equation in column C from '100sin(wt-90) + 100sin(wt-180)' to '100sin(wt+90) + 100sin(-wt)' so that the total voltage in column D better matches with the voltages from my formula in column G. The equation for column B is just the sine wave for the base wave, showing the voltage resulting to the source resistor from the peak current. The equation in column C is the same (from current) but recognizes that current from the reflected wave will cancel the current from the forward wave coming through Rs. The two waves are traveling in opposite directions so one angle must be labeled with a negative sign so that it will rotate in the opposite direction. In column C, the first term is the reflected wave and the second term is the base wave. My formula, displayed in column G, uses the applied voltage of 141.4 volts. I thought it would be easier to see how the spreadsheet was built using current to find the voltages. You can see how the results of column D match well with those from column G. I am still having difficulty matching these equations with mine. Just to make sure we are discussing the same problem.... The circuit is a voltage source Vs(t) = 141.4 sin(wt-45) driving a source resistor of 50 ohms and 45 degress of 50 ohm transmission line that is shorted at the end. My calculations suggest that Vrs.total(t) = 100 sin(wt-90) Irs.total(t) = 2 sin(wt-90) which agrees with you column D but not the introduction which says that the zero current is at 0 degrees. With -100 volts across the source resistor at 0 degrees, the current should be -2 amps through the source resistor at 0 degrees; in other words, a current maximum. Using superposition, I compute the the contribution of the source to be Vrs.source(t) = 70.7 sin(wt-45) and the contribution from the reflected wave to be Vrs.reflected(t) = -70.7 sin(wt+45) which sum to Vrs.total(t) = 100 sin(wt-90) as expected. So while I can construct an expression for Column D, the contributing values do not agree with those you have provided in Columns B and C. Column E follows from Column D and my calculations agree. And also with Column F. The spreadsheet addresses the following issues: Does the traveling wave carry power? Yes. The spreadsheet was built assuming that power is carried by traveling waves. Because the resulting wave form and powers seem correct, the underlaying assumption seems correct. It was not obvious which columns were used to draw this correlation. Column E and column F display power. Column F recognizes that if 100 watts is applied continueously (on the average) over an entire 360 degree cycle, the final power applied over time would be 360 * 100 = 36000 watt-degrees. Part of the power comes from the reflection, part comes directly. Obviously, interference is very much at work in this example. Column E is the power dissipated in the resistor, and Column F is the integral of Column and represents the total energy which has flowed in to the resistor over the cycle. It is also the average energy per cycle. If you were to extend your analysis to compute the energy in each degree of the reflected wave and add it to the energy in each degree of Vrs.source(t) and sum these, you would find that the instantaneous energy from Vrs.source and Vrs.reflected does not agree with the instantaneous energy dissipated in the source resistor. It is this disagreement that is the root of my argument that the power in the reflected wave is a dubious concept. Using averages, the computed powers support the hypothesis, but when examined with finer granularity, they do not. However, even if this experiment is consistent with the hypothesis it only takes one experiment which is not to disprove the hypothesis. True! Is power conserved on the transmission line, meaning, can the energy contained in power be conserved and located over time on the transmission line? Yes, the spreadsheet was built assuming that power could be conserved and traced over time so the underlaying assumption seems correct. Does interference occur in this example? The spreadsheet was built assuming that voltage and currents from superpose in a manner consistent with constructive and destructive interference, so the underlaying assumption seems correct. Is power stored in the reactive component for release in later in the cycle or during the next half cycle? Yes, power is stored on the transmission line during the time it takes for power to enter the line, travel to the end and return. The time of wave travel on the transmission line is related to the value of the reactive component. Does the direction of wave travel affect the measurement of voltage and the application of power to a device? Yes. A wave loses energy (and therefore voltage) as it travels through a resistance. As a result, power from the prime source is ALWAYS applied across the sum of the resistance from the resistor AND transmission line. I am not sure that I would describe this as the wave losing energy, but rather as the voltage dividing between the two impedances. If the source resistance was replaced by another transmission, which could easily be set to provide a 50 ohm impedance, would you still describe it as the wave losing energy? It should be OK to think of the voltage dividing between two impedances. The important thing is to consider how the reflected voltage sums with the forward voltage where it is measured. Because the two waves are traveling in opposite directions, the measured voltage is not the voltage applied to either Rs or the transmission line. This is why columns B and C must be added to find the total voltage across Rs. Whether one needs to add or subtract is more a matter of the convention being used for the signs of the values. When Vf and Vr are derived using Vtot = Vf + Vr; Itot = If + Ir one would expect to have to add the negative of Vr to the contribution from Vs to arrive at the total voltage across the source resistor. The spreadsheet was built using this assumption and seems correct. (At times during the cycle, the forward and reflected waves oppose, resulting in very little current through the resistor. During those times, the power applied to the transmission line is much HIGHER because the reflected wave reflects from the load and source, and merges/adds to the forward wave from the source.) I am not convinced. When there is very little current through the resistor, there is also very little current into the transmission line. This suggests to me that the power applied to the transmission line is low. I don't follow you here. Right, power into the transmission line is low when the current in is low, and it is high when the current is high. It is clear that peak current and peak voltage do not occur at the same time except when measured across the resistor in column D. Power into the transmission line is low when either the voltage or the current is low; when either is zero, the power is zero. Since the highest voltage occurs with zero current and the highest current occurs with zero voltage, maximum power into the transmission line occurs when the voltage and current are both medium; more precisely, when they are both at .707 of their maximum values. This is just one example, but it seems like the power is accounted for here. We need another example where power can NOT be accounted for. I suggest it is the same example, but the granularity of the analysis needs to be increased. ....Keith |
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Keith Dysart wrote:
Unfortunately for your hypothesis, average power is insufficient to account for energy which might be in the reflected wave. An average power analysis agrees with your hypothesis, while a more detailed instaneous analysis disproves it. One more time: My hypothesis doesn't apply to instantaneous powers at all so there is nothing to disprove. Please leave me out of any discussion of instantaneous powers. If it was just a 'suspicion' you could probably let go of the idea long enough to learn what is really happening and why it is not inconsistent with the idea that reflected wave energy is a dubious concept. One look in a mirror should convince you otherwise. You *have* found it hard to the do the math; Nope, I just think that instantaneous power math is a waste of my time. Seems to also be a waste of your time. Your explanation is not complete until you can identify the element that stores and returns the energy and its energy transfer function. I simply don't have anything at all to say about instantaneous powers. In my opinion, such is a waste of my time. You might as well be demanding that I produce the math for how many angels can dance on the head of a pin. Energy can not be destroyed. Yet, you are trying your best to destroy the energy in the reflected wave. Since you cannot destroy reflected energy at the average power level, you are trying to destroy it at the instantaneous level. -- 73, Cecil http://www.w5dxp.com |
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Keith Dysart wrote:
Perhaps you should complete part one so that it fully accounts for the energy flows before progressing to writing part two. Average is not a full accounting. Average is the only accounting that I consider to be important and the only accounting that I am going to do. I have added a disclaimer about instantaneous power to my Part 1 article. I personally don't think that anyone else cares about instantaneous powers. If you need an instantaneous power article written, please feel free to write it yourself. I wish you luck but I personally consider it to be a waste of time. -- 73, Cecil http://www.w5dxp.com |
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Keith Dysart wrote:
Using averages, the computed powers support the hypothesis, but when examined with finer granularity, they do not. Well Keith, yours also falls apart at finer granularity where you are required to determine the position and momentum of the individual charge carriers. -- 73, Cecil http://www.w5dxp.com |
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On Mar 30, 8:28*pm, Cecil Moore wrote:
Keith Dysart wrote: Unfortunately for your hypothesis, average power is insufficient to account for energy which might be in the reflected wave. An average power analysis agrees with your hypothesis, while a more detailed instaneous analysis disproves it. One more time: My hypothesis doesn't apply to instantaneous powers at all so there is nothing to disprove. Please leave me out of any discussion of instantaneous powers. You state that your hypothesis is that for this specific circuit, "the energy in the reflected wave is dissipated in the source resistor". This claim is amenable to analysis using instantaneous energy flows. When so analyzed, the hypothesis fails. I can see why you want to limit the kinds of analysis applied to your hypothesis, but that is not how science works. If you wish to narrow your hypothesis to "the average energy in the reflected wave is simply numerically equal to the increase in the average dissipation in the source resistor" I will not object since that hypothesis would be completely accurate and not misleading. As long as you wish to claim that there is actual energy in the reflected wave, and that this energy is dissipated in the source resistor, you must be prepared to offer a full accounting. If it was just a 'suspicion' you could probably let go of the idea long enough to learn what is really happening and why it is not inconsistent with the idea that reflected wave energy is a dubious concept. One look in a mirror should convince you otherwise. You *have* found it hard to the do the math; Nope, I just think that instantaneous power math is a waste of my time. Seems to also be a waste of your time. Not at all. I've learned a new (at least to me) technique for analyzing where the energy goes. I've increased my skills with complex numbers in Excel. I have a firmer grasp about power computations. I've explored the tautology of Ptotal = Pforward - Preflected. I've learned a bit about macros in Excel. I've tried Calc and found it wanting. I've looked at energy flows in circulators. I've explored active and passive circulators. And I've proved your hypothesis to be false. Not a waste at all. Your explanation is not complete until you can identify the element that stores and returns the energy and its energy transfer function. I simply don't have anything at all to say about instantaneous powers. In my opinion, such is a waste of my time. A higly convenient opinion since it allows you to continue to believe your hypothesis. You might as well be demanding that I produce the math for how many angels can dance on the head of a pin. No. Instantaneous flows *can* be computed. Angels on a pin are a little more problematic. Energy can not be destroyed. Yet, you are trying your best to destroy the energy in the reflected wave. Since you start with an unshakeable belief in the existance of energy in the reflected wave, this would be your natural conclusion. Those of us whose beliefs are not so fixed, evaluate the proofs and come to the conclusion that energy in the reflected wave is a dubious concept. Since you cannot destroy reflected energy at the average power level, you are trying to destroy it at the instantaneous level. "Average" is just a data reduction from "instantaneous". An agreement of averages is not a proof of anything except that the "averages are numerically equal". ...Keith |
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On Mar 30, 8:43*pm, Cecil Moore wrote:
Keith Dysart wrote: Perhaps you should complete part one so that it fully accounts for the energy flows before progressing to writing part two. Average is not a full accounting. Average is the only accounting that I consider to be important and the only accounting that I am going to do. I have added a disclaimer about instantaneous power to my Part 1 article. But the meaning of the disclaimer is not clear to the reader. You really need to restate your hypothesis to remove the possibility of misleading the reader. I would suggest something along the lines of "My hypothesis is that the average energy in the reflected wave is *numerically* equal to the increase in dissipation of the source resistor. It should be noted that this says nothing about whether the energy in the reflected wave is actually dissipated in the source resistor." That would be completely accurate and very unlikely to be misconstrued by the reader. I personally don't think that anyone else cares about instantaneous powers. I am sure some do not. But anyone interested in a full understanding does. If you need an instantaneous power article written, please feel free to write it yourself. I wish you luck but I personally consider it to be a waste of time. It is convenient when you just ignore the analysis that disproves your hypothesis. But it does not make the hypothesis more correct. ...Keith |
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On Mar 30, 8:48*pm, Cecil Moore wrote:
Keith Dysart wrote: Using averages, the computed powers support the hypothesis, but when examined with finer granularity, they do not. Well Keith, yours also falls apart at finer granularity where you are required to determine the position and momentum of the individual charge carriers. Perhaps, but it is highly improbable that it falls apart in a manner that ends up supporting the original failed hypothesis. ...Keith |
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Keith Dysart wrote:
You state that your hypothesis is that for this specific circuit, "the energy in the reflected wave is dissipated in the source resistor". First, let's correct your out-of-context quotation. Here is what you should have quoted: "When zero interference exists at the source resistor, the energy in the reflected wave is dissipated in the source resistor." This is actually a fact for both average powers and instantaneous powers. Since all of your examples are associated with a non-zero level of interference, they are irrelevant to the stated conditions. Here is a quote from that article: "Please note that any power referred to in this paper is an AVERAGE POWER. Instantaneous power is irrelevant to the following discussion." The word "average" is implied in every statement I make. This claim is amenable to analysis using instantaneous energy flows. When so analyzed, the hypothesis fails. No, it doesn't fail. You have simply failed to satisfy the zero interference precondition. If you wish to narrow your hypothesis to "the average energy in the reflected wave is simply numerically equal to the increase in the average dissipation in the source resistor" I will not object since that hypothesis would be completely accurate and not misleading. That is, in fact, the only hypothesis presented in my Part 1 article. Since my hypothesis never applied to instantaneous power, I don't have to narrow the hypothesis. My article stands as written. Please cease and desist with the unfair innuendo. Not a waste at all. Obviously, your opinion differs from mine. To the best of my knowledge, you are the first person to spend any mental effort on instantaneous power. If that's what you want to do, be my guest. I consider it to be little more than mental masturbation, "of limited utility" as Hecht said. In fact, I proved my assertion was true even at the instantaneous power level when the "zero interference" precondition is met. Since you start with an unshakeable belief in the existance of energy in the reflected wave, this would be your natural conclusion. Since you are incapable of producing an EM wave devoid of energy (or an angel dancing on the head of a pin) both concepts are unrelated to reality IMO. Your challenge is the same as it has always been. Just produce an EM wave containing zero energy and get it over with. -- 73, Cecil http://www.w5dxp.com |
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Keith Dysart wrote:
But the meaning of the disclaimer is not clear to the reader. You really need to restate your hypothesis to remove the possibility of misleading the reader. What is it about "Please note that any power referred to in this paper is an AVERAGE POWER. Instantaneous power is irrelevant to the following discussion." that you do not understand? I would suggest ... I would suggest that you write your own article. Mine stands as written in the *stated context* of zero interference and average powers. I am not interested in attempting a unified theory of everything. I personally don't think that anyone else cares about instantaneous powers. I am sure some do not. But anyone interested in a full understanding does. Anyone interested in a *full* understanding would take the discussion down to the quantum level which, interestingly enough, you have chosen to ignore. It is convenient when you just ignore the analysis that disproves your hypothesis. But it does not make the hypothesis more correct. If you think your unethical innuendo, out-of-context quotes, and straw man arguments disprove anything, I feel sorry for you. Once again, the context of my Part 1 assertions is *ZERO INTERFERENCE* and *AVERAGE POWERS*. You have disproved nothing so far. You were even taken aback when it was true at the instantaneous level in the context of zero instantaneous interference. -- 73, Cecil http://www.w5dxp.com |
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Keith Dysart wrote:
Perhaps, but it is highly improbable that it falls apart in a manner that ends up supporting the original failed hypothesis. Since the original hypothesis is in the context of zero interference (and average powers) it has not failed. So far, I have made no assertions about conditions when interference is present as it is in all of your examples. None of your observations are relevant to my Part 1 article because they are all outside the stated context of the article. The challenge for you is to present a zero interference example for which my hypothesis is false. So far, you have failed to do so. I have asserted, "If zero interference exists, then 'A' is true". You have said 'A' is not true when interference exists. I actually agree with you but it is irrelevant to the stated 'if' portion of my premise. Where did you study logic? Maybe you don't realize that if the 'if' portion of an 'if/then' statement is false, the entire statement is true, by definition. My assertions about conditions when interference is present will appear in Parts 2 and 3 (which would have been completed by now if I had ignored your diversions). -- 73, Cecil http://www.w5dxp.com |
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On Sun, 30 Mar 2008 07:43:59 -0700 (PDT)
Keith Dysart wrote: On Mar 29, 7:18 pm, Roger Sparks wrote: On Sat, 29 Mar 2008 12:45:48 -0700 (PDT) Keith Dysart wrote: On Mar 27, 2:06 am, Roger Sparks wrote: Cecil Moore wrote: Roger Sparks wrote: You need to take a look at the spreadsheets. clip http://www.fairpoint.net/~rsparks/Sm...Reflection.pdf clip I am still having difficulty matching these equations with mine. Just to make sure we are discussing the same problem.... As I tried to understand your problem, I finally realized that it was really my problem. As a result, I redid the spreadsheet. I now label "my formula" as being erroneous, this because it does relate to the current, not the voltage, and must be displaced by 45 degrees. My formula (labeled erroneous) was the result of the formulas of columns B and C added with trig identities. What I did not realize was that the adding, while correct, rotates the phase. The formula is wrong because it does not recognize the phase shift that had been assumed for line one. The spreadsheet addresses the following issues: Does the traveling wave carry power? Yes. The spreadsheet was built assuming that power is carried by traveling waves. Because the resulting wave form and powers seem correct, the underlaying assumption seems correct. It was not obvious which columns were used to draw this correlation. Column E and column F display power. Column F recognizes that if 100 watts is applied continueously (on the average) over an entire 360 degree cycle, the final power applied over time would be 360 * 100 = 36000 watt-degrees. Part of the power comes from the reflection, part comes directly. Obviously, interference is very much at work in this example. Column E is the power dissipated in the resistor, and Column F is the integral of Column and represents the total energy which has flowed in to the resistor over the cycle. It is also the average energy per cycle. If you were to extend your analysis to compute the energy in each degree of the reflected wave and add it to the energy in each degree of Vrs.source(t) and sum these, you would find that the instantaneous energy from Vrs.source and Vrs.reflected does not agree with the instantaneous energy dissipated in the source resistor. It is this disagreement that is the root of my argument that the power in the reflected wave is a dubious concept. I think the energy adds correctly now. Of course it depends upon how we measure the energy because energy is stored in the transmission line at all times, but the stored energy is only measured across either Rs or the transmission line. We do not measure the energy within the transmission line in this example, which is the sum of the applied power for 90 degrees. Using averages, the computed powers support the hypothesis, but when examined with finer granularity, they do not. I think each degree has the correct power now. I apologize for the errors, and hope that I have them all removed. However, even if this experiment is consistent with the hypothesis it only takes one experiment which is not to disprove the hypothesis. True! Is power conserved on the transmission line, meaning, can the energy contained in power be conserved and located over time on the transmission line? Yes, the spreadsheet was built assuming that power could be conserved and traced over time so the underlaying assumption seems correct. Does interference occur in this example? The spreadsheet was built assuming that voltage and currents from superpose in a manner consistent with constructive and destructive interference, so the underlaying assumption seems correct. Is power stored in the reactive component for release in later in the cycle or during the next half cycle? Yes, power is stored on the transmission line during the time it takes for power to enter the line, travel to the end and return. The time of wave travel on the transmission line is related to the value of the reactive component. Does the direction of wave travel affect the measurement of voltage and the application of power to a device? Yes. A wave loses energy (and therefore voltage) as it travels through a resistance. As a result, power from the prime source is ALWAYS applied across the sum of the resistance from the resistor AND transmission line. I am not sure that I would describe this as the wave losing energy, but rather as the voltage dividing between the two impedances. If the source resistance was replaced by another transmission, which could easily be set to provide a 50 ohm impedance, would you still describe it as the wave losing energy? It should be OK to think of the voltage dividing between two impedances. The important thing is to consider how the reflected voltage sums with the forward voltage where it is measured. Because the two waves are traveling in opposite directions, the measured voltage is not the voltage applied to either Rs or the transmission line. This is why columns B and C must be added to find the total voltage across Rs. Whether one needs to add or subtract is more a matter of the convention being used for the signs of the values. When Vf and Vr are derived using Vtot = Vf + Vr; Itot = If + Ir one would expect to have to add the negative of Vr to the contribution from Vs to arrive at the total voltage across the source resistor. The spreadsheet was built using this assumption and seems correct. (At times during the cycle, the forward and reflected waves oppose, resulting in very little current through the resistor. During those times, the power applied to the transmission line is much HIGHER because the reflected wave reflects from the load and source, and merges/adds to the forward wave from the source.) I am not convinced. When there is very little current through the resistor, there is also very little current into the transmission line. This suggests to me that the power applied to the transmission line is low. I don't follow you here. Right, power into the transmission line is low when the current in is low, and it is high when the current is high. It is clear that peak current and peak voltage do not occur at the same time except when measured across the resistor in column D. Power into the transmission line is low when either the voltage or the current is low; when either is zero, the power is zero. Since the highest voltage occurs with zero current and the highest current occurs with zero voltage, maximum power into the transmission line occurs when the voltage and current are both medium; more precisely, when they are both at .707 of their maximum values. This is just one example, but it seems like the power is accounted for here. We need another example where power can NOT be accounted for. I suggest it is the same example, but the granularity of the analysis needs to be increased. ...Keith I hope I have the spread sheet displaying correct values now. Thank you for your careful analysis. I doubt that this will satisfy your power location concerns because the spread sheet shows more power being delivered to the resistor than is present in the voltage. This is because the impedance of the power equation has changed due to the contribution of the current component. Consider that for columns B and C, the same current flows whether the voltage in B is applied or the voltage in C is applied. This can only happen if the impedance seen by each respective voltage is different. This is interference at work -- 73, Roger, W7WKB |
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On Mon, 31 Mar 2008 10:03:52 -0700
Roger Sparks wrote: On Sun, 30 Mar 2008 07:43:59 -0700 (PDT) Keith Dysart wrote: On Mar 29, 7:18 pm, Roger Sparks wrote: On Sat, 29 Mar 2008 12:45:48 -0700 (PDT) Keith Dysart wrote: On Mar 27, 2:06 am, Roger Sparks wrote: Cecil Moore wrote: Roger Sparks wrote: You need to take a look at the spreadsheets. clip http://www.fairpoint.net/~rsparks/Sm...Reflection.pdf clip I doubt that this will satisfy your power location concerns because the spread sheet shows more power being delivered to the resistor than is present in the voltage. This is because the impedance of the power equation has changed due to the contribution of the current component. Consider that for columns B and C, the same current flows whether the voltage in B is applied or the voltage in C is applied. This can only happen if the impedance seen by each respective voltage is different. This is interference at work -- 73, Roger, W7WKB After posting previosly, I got to thinking that interference here is wrecking the analysis of Column D. The traveling wave analysis is correct (Column H). Only one current is flowing through Rs, and the current is not enough to supply the power suggested in column D. While it is logical to add the voltages from Column B and Column C, the two voltages are often in opposition so they are not "seen" by Rs. As a result, we must have a reflection from Rs that I am not taking into account. -- 73, Roger, W7WKB |
The Rest of the Story
On Mar 31, 2:22*pm, Roger Sparks wrote:
On Mon, 31 Mar 2008 10:03:52 -0700 Roger Sparks wrote: On Sun, 30 Mar 2008 07:43:59 -0700 (PDT) Keith Dysart wrote: On Mar 29, 7:18 pm, Roger Sparks wrote: On Sat, 29 Mar 2008 12:45:48 -0700 (PDT) Keith Dysart wrote: On Mar 27, 2:06 am, Roger Sparks wrote: Cecil Moore wrote: Roger Sparks wrote: You need to take a look at the spreadsheets. clip http://www.fairpoint.net/~rsparks/Sm...Reflection.pdf clip I doubt that this will satisfy your power location concerns because the spread sheet shows more power being delivered to the resistor than is present in the voltage. *This is because the impedance of the power equation has changed due to the contribution of the current component. Consider that for columns B and C, the same current flows whether the voltage in B is applied or the voltage in C is applied. *This can only happen if the impedance seen by each respective voltage is different. *This is interference at work * -- 73, Roger, W7WKB After posting previosly, I got to thinking that interference here is wrecking the analysis of Column D. *The traveling wave analysis is correct (Column H). *Only one current is flowing through Rs, and the current is not enough to supply the power suggested in column D. *While it is logical to add the voltages from Column B and Column C, the two voltages are often in opposition so they are not "seen" by Rs. *As a result, we must have a reflection from Rs that I am not taking into account. * Column B is correct; this being the voltage produced by the source divided by two. It is also the forward voltage on the line. Vrs.source(t) = Vf(t) = 70.7 sin(wt) Column C is the reflected voltage (not the reflected voltage impressed across the source resistor). The reflection coefficient is -1, and the delay is 90 degrees so the reflected voltage at the generator is Vr(t) = -1 * Vf(t - 90 degrees) = - 70.7 sin(wt-90) = 70.7 sin(wt+90) But Vr is impressed across the resistor in the opposite direction to that of Vrs.source, so the equation for total Vrs is Vrs.total(t) = Vrs.source(t) - Vr(t) thus column D should be B31-C31. Alternatively, Vrs.reflect(t) = -Vr(t) and then Vrs.total(t) = Vrs.source(t) + Vrs.reflect(t) Column E is correctly computing the instantaneous power from Column D since P(t) = V(t) * I(t) = V(t) * V(t) / R = V(t) * V(t) / 50 (in this example) but has the wrong data because of the error in Column D. Column F is integrating the power to yield either the energy in a cycle or the average power per cycle (though presented in unusual units). I agree G is erroneous and I am not sure what H is computing. ...Keith |
The Rest of the Story
Roger Sparks wrote:
While it is logical to add the voltages from Column B and Column C, the two voltages are often in opposition so they are not "seen" by Rs. As a result, we must have a reflection from Rs that I am not taking into account. It's not a "reflection" of a single wave, Roger, it is a "redistribution" of energy caused by superposition of two waves accompanied by interference. Eugene Hecht explains it all in Chapter 9: Interference in "Optics". For anyone who thinks he is already omniscient about EM waves, I would highly recommend reading Hecht's chapter on interference. -- 73, Cecil http://www.w5dxp.com |
The Rest of the Story
On Mon, 31 Mar 2008 19:11:56 -0500
Cecil Moore wrote: Roger Sparks wrote: While it is logical to add the voltages from Column B and Column C, the two voltages are often in opposition so they are not "seen" by Rs. As a result, we must have a reflection from Rs that I am not taking into account. It's not a "reflection" of a single wave, Roger, it is a "redistribution" of energy caused by superposition of two waves accompanied by interference. Eugene Hecht explains it all in Chapter 9: Interference in "Optics". For anyone who thinks he is already omniscient about EM waves, I would highly recommend reading Hecht's chapter on interference. -- 73, Cecil http://www.w5dxp.com I had to chuckle when I read this Cecil. First I looked up the word "omniscient" to refresh my memory about meaning, but then I thought "anyone who thinks he is omniscient is not about to read the works of others and learn new tricks". Just human nature. You can see from my postings that I am still trying to better understand the wave and reflections, still looking how to describe the energy distribution within the cycle. The storage of the redistributed energy must be close to the wires of the circuit so we should be able to describe it mathmatically, if I just knew how. We are probably close on the spreadsheet, but it is not yet crystal clear in my mind. -- 73, Roger, W7WKB |
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