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Reg Edwards wrote:
"Cecil Moore" wrote If forward and reverse waves do not exist separately, how is it possible for a circulator to separate them? You forgot to allow TIME into the argument. The two waves do NOT, and cannot, exist seperately in time. I'm not sure what your point is. If a laser beam is aimed at a mirror, do the forward wave and reflected wave exist separately in time? If we send a forward wave down a one-second lossless feedline for one second and turn it off, nothing happens for one second. Then we receive a reflected wave for one second. Do those waves not exist separately in time? The circulator merely divides the STEADY STATE, instantaneous, at the same time, power in the wave into two parts according to what the operator, or by design, has set it to do. The point is that one of those parts has made a round trip to the load and back as can be proved by observing ghosting in TV signals. When the generator is switched off both parts disappear simultaneously. Not entirely true. The reflected wave would continue to exist until the energy in the transmission line is dissipated. -- 73, Cecil, http://www.qsl.net/w5dxp |
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Cecil Moore wrote:
Gene Fuller wrote: If you refuse to accept standard technical conventions, then there is little hope of getting others to agree with you. Gene, have you stopped beating your wife? Your usual ad hominem attack completely devoid of any technical content is duly noted. In a one second long lossless transmission line where the forward power is 200W and the reflected power is 100W, it can be proved that the source has supplied 300 joules that have not been accepted by the load. If those joules are not contained in the forward and reflected waves, where are they? Cecil, I recall that you selectively quote only those parts of messages to which you disagree. I guess you accepted the remainder of my comments. You quite clearly said that "steady state" is not really steady. I challenged that in a straight-forward manner. So what is "ad hominem" about my message? ad-hominem This is a typical trick, Cecil, when you have been caught dealing nonsense. You ignore the issue and attempt diversion. It won't work here. The meaning of steady state is not controversial. /ad-hominem 73, Gene W4SZ |
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Cecil Moore wrote:
Gene Fuller wrote: If you refuse to accept standard technical conventions, then there is little hope of getting others to agree with you. I am advocating the wave reflection model as explained in: Johnson's, "Transmission Lines and Networks", 1st Edition Ramo/Whinnery's, "Fields and Waves in Modern Radio", 2nd Edition Hecht's, "Optics", 4th Edition Maxwell's, "Reflections" and "Reflections II" "The ARRL Antenna Book", 15th Edition I am also advocating the conservation of energy principle. I hope that one doesn't need references. Exactly what is it about the wave reflection model and the conservation of energy principle with which you disagree? Cecil, My only comment was in regard to the definition of steady state. I am not sure why you directed this list to me. I have three out of the five references you list, and I have multiple equivalents for the others. 73, Gene W4SZ |
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Gene Fuller wrote:
You quite clearly said that "steady state" is not really steady. No I didn't. You either misunderstood or are trying to set up a straw man. The meaning of steady state is not controversial. I never said it was so this is just another one of your straw men. -- 73, Cecil, http://www.qsl.net/w5dxp |
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Gene Fuller wrote:
My only comment was in regard to the definition of steady state. I doubt that we have different definitions of "steady-state". I didn't post a definition and I don't recall you posting one. What I said was that some of the 300 joules existing in the one second long transmission line during steady-state was supplied by the source before steady-state was reached, i.e. during the initial transient state. -- 73, Cecil, http://www.qsl.net/w5dxp |
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Hey Cecil,
Can you sum up the problem with conservation of energy that modern RF textbooks get wrong? Dan |
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Cecil Moore wrote:
Gene Fuller wrote: You quite clearly said that "steady state" is not really steady. No I didn't. You either misunderstood or are trying to set up a straw man. The meaning of steady state is not controversial. I never said it was so this is just another one of your straw men. Cecil, Your exact words we *** Steady-state had a beginning and it will have an end. It cannot be analyzed without knowing what happened in the beginning and what will happen in the end. Steady-state is the rug under which you and others try to sweep the laws of physics including the conservation of energy principle. I'm doing what I can to call your bluff. *** This says that steady state depends on something else, namely the beginning and the end of the steady state condition. That is simply incorrect. In steady state conditions there is no concept of beginning or end. ad hominem If you don't know the rules, you can't play the game. /ad hominem 73, Gene W4SZ |
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wrote:
Can you sum up the problem with conservation of energy that modern RF textbooks get wrong? They don't get it wrong - they just don't discuss it at all. But here is an example of the problem: http://eznec.com/misc/food_for_thought/ First article - last paragraph. W7EL considers steady-state conditions while ignoring the previous transient state conditions. He implies that the energy in the reflected wave cannot be recovered but it is indeed dissipated as power in the system after power is removed from the source. The source supplies exactly the amount of energy during the transient power up conditions needed to support the forward and reflected waves during steady-state. This is easy to prove. But W7EL's Ivory Tower protects Him from peons like me. -- 73, Cecil http://www.qsl.net/w5dxp |
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Gene Fuller wrote:
This says that steady state depends on something else, namely the beginning and the end of the steady state condition. That is simply incorrect. In steady state conditions there is no concept of beginning or end. A 12VDC battery is sitting there with a 200 amp*hour charge. Are you asserting that there is no concept of where the 200 amp*hours came from? Please tell me you are not that stupid. Consider the one second long transmission line with 200W of forward power and 100W of reflected power. That requires 300 joules of energy during steady-state. If the 300 joules was not supplied during the transient state, then it must have magically appeared out of thin air in violation of the conservation of energy principle? Is that what you are trying to tell us? -- 73, Cecil http://www.qsl.net/w5dxp |
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The net power flux in the line gets smaller as the reflected wave gets
stronger while maintaining a constant electric field (constant voltage as in Roy's example). If you can match to the new impedance at the line input; that is, make the electric fields both stronger, you can get a larger net power flux even in the presence of some elevated SWR. See LaTeX formatted math at http://en.wikipedia.org/wiki/User:Dan_Zimmerman/Sandbox The flux of stored power in the line, interestingly enough, is a sinusoidal function of position. I'm still thinking what to make of it, but I thought I'd post the math for people to look at (and check, please!!!!) ... I'll be back later. 73, Dan |
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Cecil Moore wrote:
Gene Fuller wrote: This says that steady state depends on something else, namely the beginning and the end of the steady state condition. That is simply incorrect. In steady state conditions there is no concept of beginning or end. A 12VDC battery is sitting there with a 200 amp*hour charge. Are you asserting that there is no concept of where the 200 amp*hours came from? Please tell me you are not that stupid. Consider the one second long transmission line with 200W of forward power and 100W of reflected power. That requires 300 joules of energy during steady-state. If the 300 joules was not supplied during the transient state, then it must have magically appeared out of thin air in violation of the conservation of energy principle? Is that what you are trying to tell us? Cecil, You can wave your hands all you want, but it won't have much impact on the correct math and physics. Try writing the appropriate equations for your puzzler, in steady state conditions, and then figure out where to insert the transient behavior. Good luck. This is basic stuff taught in numerous math and technical courses. If don't accept the basic math, then I guess we will not agree. 73, Gene W4SZ |
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Gene Fuller wrote:
Try writing the appropriate equations for your puzzler, in steady state conditions, and then figure out where to insert the transient behavior. I have already provided the equations, Gene. In a one second long lossless transmission line, 200 watts of forward power equals 200 joules of energy in the forward wave. 100 watts of reflected power equals 100 joules in the reflected wave. Total joules in the transmission line equals 200 + 100 = 300 joules. The equations are trivial. -- 73, Cecil, W5DXP |
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On Sat, 26 Aug 2006 02:33:03 GMT, Gene Fuller
wrote: Cecil Moore wrote: Gene Fuller wrote: In steady state conditions there is no concept of beginning or end. If the 300 joules was not supplied during the transient state, then it must have magically appeared out of thin air in violation of the conservation of energy principle? Hi Gene, The bare contradiction is enough to condemn this thread. However, it does have its amusing character of "Who's on first?" Continuing that metaphor, Cecil would believe having been born on third base, that he had hit a triple to be there. ;-) 73's Richard Clark, KB7QHC |
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On Fri, 25 Aug 2006 20:10:14 -0700, Richard Clark
wrote: Continuing that metaphor, Cecil would believe having been born on third base, that he had hit a triple to be there. ;-) For the concept challenged, Being on third is the steady state. The transient state is one of: Being born; hitting a triple; hitting a double and then a batter advancing the runner(s); hitting a single (then like wise with the batter's assist); stealing a base; or two. The steady state also has to satisify other conditions that were taken up by transients like outs and innings. e.g. being on third with three outs does not mean you can stay on third. Thus the next transient is The side is retired (state change) or, as in this case of the bottom of the ninth and an untied score The game is over (solution). 73's Richard Clark, KB7QHC |
Error correction
A correction - insert dt instead of dz.
The fundamental partial differential equations of transmission lines are - - dv/dz = R + L*di/dt - di/dz = G + C*dv/dt where volts v and current i are incremental functions of distance and time, and z is incremental distance along line. Everything else follows. Similar equations can be written in terms of frequency. It is often easier to think in terms of Time and Distance rather than Frequency and Impedance. ---- Reg. |
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Cecil Moore wrote:
If I understand correctly, Roy's argument is that since the source is not supplying any steady-state energy to the lossless stub, there is no energy in the reflected wave within the stub. That sounds right... if the reflection coefficient is 1 then there's no net power flux into/through the line in steady state, and this can be described if you like by counterpropagating waves each carrying the same amount of energy. The problem is, in your other example where you say 200 joules in the forward wave + 100 joules in the reflected wave = 300 joules in the line total, you're neglecting the vector character of the power flux. Yes, the waves carry energy, but they carry it in different directions. The net power flux in the line with 200W forward power and 100W reflected power is 100W net power flowing to the load from the source. The real part of the Poynting vector of the reflected wave opposes that of the forward wave, as long as I got all the signs right. I don't think we can neglect the imaginary part of the Poynting vector, though. It's not zero and I think it represents the flow of the power in the stored fields in the line, and if we want to get the total energy in the line, we have to include the stored fields. Dan |
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Richard Clark wrote:
Continuing that metaphor, Cecil would believe having been born on third base, that he had hit a triple to be there. ;-) That is actually the other side of the argument. When an observer arrived after the game started, Cecil was on third base. Using steady-state logic, the newcomer assumes that Cecil is there without ever having to swing a bat. Someone looks at a transmission line during steady-state. The source is supplying 100 watts. The load is dissipating 100 watts. The forward power is 200 watts. The reflected power is 100 watts. The incorrect assumption is that the source is incapable of delivering the 200 watts of forward power and the 100 watts of reflected power. But the exact amount of energy required to support those values was provided to the transmission line before steady- state was reached. It was rejected by the load and is still there in the transmission line during steady-state. -- 73, Cecil http://www.qsl.net/w5dxp |
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Cecil,
You've set up a false dichotomy here. When I, and others, write "The electric field is the superposition of a forward and reverse traveling wave" maybe it would be better to say "The electric field has two terms, one that appears to be a forward traveling wave and one that appears to be a reverse traveling wave." or something like that. There's one electric field vector and one Poynting vector. Or there are two. The structure of the electric field and the structure of the real part of the Poynting vector both admit BOTH explanations of what's happening. You're not gonna get 300J in your one second line.... the stored energy flux in the line depends on the wavelength of the incident RF, and in retrospect, you might expect this from the fact that a misterminated line goes through cyclical impedance variations as you change its length (something that I know you're quite familiar with :-) ) I think the energy density per unit length in the line is proportional to the Poynting vector (or it's integral over the cable cross section, and the proportionality constant is the group velocity of the waves, I think) I left Jackson at work, so I'm not certain right now. What I am certain of is that you can't take the energy in the forward wave and add it to the energy of the reflected wave and get that there are 300J in a 1 second line carrying a 200W forward wave and a 100W reverse wave. Rather, there's a 100W net forward power flux and THAT will give you the energy contained in the part of the field that's actually moving from source to load. The energy contained in the reactive part has an integral that's going to cyclically vary with the length of the line, and sometimes goes through zero (kL or kL - phi equal to an integer multiple of Pi... or any integer multiple of a half wavelength, which happens to be the length of an impedance repeating line, eh?) Dan |
Error correction
Reg Edwards wrote:
A correction - insert dt instead of dz. Another correction is in order. The resistive term should be i(z) * R and the conductance term should be v(z) * G. The fundamental partial differential equations of transmission lines are - - dv/dz = R + L*di/dt - di/dz = G + C*dv/dt where volts v and current i are incremental functions of distance and time, and z is incremental distance along line. bart |
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On Sat, 26 Aug 2006 12:02:14 GMT, Cecil Moore
wrote: the newcomer assumes that Cecil is there without ever having to swing a bat. The "newcomer" must be defined in the IEEE dictionary as "dolt" given there are many possible solutions, and only a dolt (obviously not a fan) would come to only ONE conclusion and that one being the least likely in baseball experience. The fan sitting next to him, hearing this exclamation is undoubtedly squirming in his seat. That dolt has left unexpressed how, without swinging a bat, that the runner was advanced to third, or worse, that he got there on the basis of not swinging a bat alone - clearly a violation of laws of baseball. Let's consider another conundrum. The dolt, having arrived late, now perceives: 1. the returned, fielded ball held by the catcher standing on home; 2. three bases loaded with runners; 3. a runner on the base line; 4. the scoreboard reveals this is the bottom of the ninth with two outs. Are there 4 men in the transmission line, or only three with the mismatched termination at the load of home base? The dolt would tell the fan next to him four (using specious math); the fan would say none (using the laws of baseball). Solution = the umpire would agree with the fan - and the side retires, the game is over. In the transient end-of-state, it takes a few minutes before the dolt realizes 1. the solution; 2. he has no beer; 3. there are 75000 fans in the exits between him and his car; 4. Luigi is going to be waiting for him to cover his lost sucker bet; 5. he has no beer. |
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Cecil Moore wrote:
[snip] Some people on this newsgroup say that the wave reflection model is invalid, that forward and reflected waves don't have a separate existence. From QEX: "Contrary to popular views, the forward and reverse waves on a transmission line are not separate fields." It would follow that a laser beam normally incident upon an ideal mirror results in a beam of light not superposed from separate forward and reverse fields. I have challenged people holding those concepts to create a standing wave without superposing separate forward and reverse waves and have gotten zero responses. Cecil, I believe Dan has addressed this issue, and I am sure that I have on many occasions. When superposition applies, as it does in this linear, non-pathological case, there is no difference between the reality of the components vs. the reality of the sum. In other words, there is no more information from your separation of a standing wave into forward and reverse components than there is in the standing wave itself. The standing wave is a perfectly good and complete solution to the wave equations applicable to this steady-state problem. It is possible to sub-divide in many ways, but there is no new information in doing so. If you want to specifically address transients then another set of equations will be needed. ad hominem You have railed against seduction by math models on many occasions. However, that is exactly what you are doing here. Trying to create some new physical reality by manipulating the numbers. /ad hominem 73, Gene W4SZ |
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Cecil Moore wrote:
Gene Fuller wrote: Try writing the appropriate equations for your puzzler, in steady state conditions, and then figure out where to insert the transient behavior. I have already provided the equations, Gene. In a one second long lossless transmission line, 200 watts of forward power equals 200 joules of energy in the forward wave. 100 watts of reflected power equals 100 joules in the reflected wave. Total joules in the transmission line equals 200 + 100 = 300 joules. The equations are trivial. -- 73, Cecil, W5DXP Cecil, Gee, somehow I can't quite pull the wave equations out of your "trivial" response. 73, Gene W4SZ |
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wrote:
When I, and others, write "The electric field is the superposition of a forward and reverse traveling wave" maybe it would be better to say "The electric field has two terms, one that appears to be a forward traveling wave and one that appears to be a reverse traveling wave." or something like that. There's one electric field vector and one Poynting vector. Or there are two. The structure of the electric field and the structure of the real part of the Poynting vector both admit BOTH explanations of what's happening. I know and accept both explanations. The problem is the other side refuses to acknowledge the validity of the wave reflection model. If you have gotten the idea that I reject the superposed wave model, you are mistaken. I fully accept both models. The problem is that others have rejected the non-superposed component wave model. I contend that one gets the same results using the components of superposition, i.e. the forward wave and the reflected wave, that one obtains after the superposition of those two waves. Others say that is an invalid treatment because superposition causes the reflected wave to cease to exist and the energy just "sloshes" around inside the transmission line. (Never mind that RF energy must necessarily travel at the speed of light and only reverses direction at an impedance discontinuity.) Rather, there's a 100W net forward power flux and THAT will give you the energy contained in the part of the field that's actually moving from source to load. The energy contained in the reactive part has an integral that's going to cyclically vary with the length of the line, and sometimes goes through zero (kL or kL - phi equal to an integer multiple of Pi... or any integer multiple of a half wavelength, which happens to be the length of an impedance repeating line, eh?) That's one model. The other model is, assuming a purely resistive Z0, the forward voltage is in phase with the forward current and therefore there are no reactive vars in the forward wave. The reflected voltage is in phase with the reflected current and therefore there are no reactive vars in the reflected wave. This model works just as well as the one above, sometimes better because of simplicity. It has the advantage of being easily able to track the real energy because there is no "unreal" energy in the model. :-) If the forward wave component is analyzed separately, there are no vars because the forward voltage is in zero phase with the forward current (assuming a perfectly resistive Z0). The same is true for the reflected wave. So we are easily able to calculate how much energy is contained in those two waves devoid of any calculation of vars. Assume that we have a one megahertz signal into a transmission line that is electrically 360 degrees long, near lossless, the forward power is 200W, and the reflected power is 100W. I am willing to bet the energy contained in the feedline during steady-state is very close to 300 microjoules no matter how complicated the math used to get the answer that I just came up with off the top of my head. Note that the transmission line is one millionth of a second long and therefore contains one millionth of the energy of a one second long line. -- 73, Cecil http://www.qsl.net/w5dxp |
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I say it's 100 microjoules.
200W forward - 100W reverse = 100W net forward power. The percieved issue of some people not believing in the seperate forward and reflected waves just doesn't come in here... it's that the real part of the Poynting vector is REDUCED by reflections. If you want to contest this point then you need to tell me where the sign error is. If you have a constant voltage (constant electric field) output on your radio then this effect actually causes LOSS of power transfer through even a lossless line. You've got a 200W matched condition, power flux is 200W. You have 100W reflected wave, you get a net power flux of 200W - 100W = 100W. You can see this from the Poynting vector which is proportional to the difference of the squares of the electric field amplitudes of the forward and reflected waves. You can also do this with lumped circut impedance analysis too. If you can't bump Ef up by using an impedance matching network, the net power flux is REDUCED by the reflected wave, and as such, the stored energy in the fields in the line is ALSO reduced. If you can increase the forward electric field in the face of mismatch, you can push the 200W into the load. The reflected wave makes it so you need more voltage to push RF down the coax. Not 300 microjoules. 100 microjoules. The energy per unit length in the line is proportional to the Poynting vector. Dan |
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Gene Fuller wrote:
When superposition applies, as it does in this linear, non-pathological case, there is no difference between the reality of the components vs. the reality of the sum. I accept both methods of analysis. What I object to is people rejecting the wave reflection model. e.g. "Reflected waves don't really exist and don't really contain any energy." As in the earlier discussion about standing wave phase, you and I wind up on the same side of the argument. What I object to is the irrational conclusions drawn by proponents of the standing wave analysis. Here are some of the past assertions: Forward waves and reflected waves cease to exist after they have been superposed. The standing wave is all that is left. Question: If the components of superposition cease to exist, doesn't that mean the products of superposition also cease to exist? (No answer) Standing waves don't require a forward wave and a reflected wave. Question: How does one obtain a standing wave without a forward traveling wave and a reverse traveling wave? (No answer) You have railed against seduction by math models on many occasions. I have railed against the assertions that superposition destroys forward and reflected waves such that they cease to exist in reality. From a recent QEX article: "I wish to emphasize the fact that the forward and reverse waves really do not exist separately, ..." So I ask you, Gene, if forward waves and reverse waves do not exist separately, how can they possibly be superposed? Seems to me, the above statement from QEX is a violation of cause and effect. If forward waves and reverse waves do not exist separately, how can they possibly be separated by a circulator? -- 73, Cecil http://www.qsl.net/w5dxp |
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wrote:
I say it's 100 microjoules. 200W forward - 100W reverse = 100W net forward power. Sorry Dan, you are right about the power and wrong about the energy. There are indeed 100 watts of *net* power. But we are not talking about the net energy delivered to the load. We are talking about the total energy in the transmission line and there's no such thing (to the best of my knowledge) as negative energy. Forward traveling energy is positive energy. Reverse traveling energy is positive energy. The energy rejected by the load is NOT negative energy. Forward traveling energy and reverse traveling energy add, not subtract. Hint: Two energy components cannot superpose to a zero scalar value. The result is always a scalar sum. If we have 200 microjoules in the forward wave and we have 100 microjoules in the reflected wave, the total energy in the transmission line is 300 microjoules. If the standing wave model differs from that amount, it is wrong. You can see this from the Poynting vector which is proportional to the difference of the squares of the electric field amplitudes of the forward and reflected waves. True for net watts, not true for joules. In the standing wave model, there's 100 watts of net power containing 100 microjoules. The other 200 microjoules are stored in the (virtual) reactances. If you calculate the energy necessarily stored in the L and C of the line, you will find the other 200 microjoules. I would have to hit the books to refresh my memory on that calculation but any other result would violate the conservation of energy principle. If you can't bump Ef up by using an impedance matching network, the net power flux is REDUCED by the reflected wave, and as such, the stored energy in the fields in the line is ALSO reduced. That applies to the watts. It doesn't apply to the vars. The actual voltages and currents are increased by the standing waves while the phase angle goes non-zero. Vars require real energy. That real energy can be calculated by knowing the current through a perfect inductor and/or the voltage across a real capacitor. Not 300 microjoules. 100 microjoules. The energy per unit length in the line is proportional to the Poynting vector. The energy per unit length is not proportional to the net Poynting vector which is (Pz+ - Pz-) (using Ramo/Whinnery conventions). The energy per unit length is actually (Pz+ + Pz-). Why that has to be true is contained in the conservation of energy principle and is the source of confusion for many posters on this newsgroup. Hint: Has anyone ever seen a quart of negative water? -- 73, Cecil http://www.qsl.net/w5dxp |
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I'll find the book.
I see what you're saying, but I'd like to work through in detail. What page should I be looking on?... I'll get back to you on Monday; Ramo and Whinnery's "Fields and Waves..." is in the UMCP library. Dan |
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wrote:
I see what you're saying, but I'd like to work through in detail. What page should I be looking on?... I'll get back to you on Monday; Ramo and Whinnery's "Fields and Waves..." is in the UMCP library. You won't find exactly what I am saying in Ramo/Whinnery. I'm pre-assuming that you accept the conservation of energy principle. :-) My 1950's Texas A&M college textbook was, "Fields and Waves in Modern Radio", by Ramo/Whinnery, 2nd edition pp 284-296. -- 73, Cecil http://www.qsl.net/w5dxp |
Error correction
Reg Edwards wrote:
A correction - insert dt instead of dz. Another correction is in order. The resistive term should be i(z) * R and the conductance term should be v(z) * G. The fundamental partial differential equations of transmission lines are - - dv/dz = R + L*di/dt - di/dz = G + C*dv/dt where volts v and current i are incremental functions of distance and time, and z is incremental distance along line. bart |
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I've come around to that conservation of energy stuff ;-)
I understand that your argument involves the energy that enters the line before it knows anything about the load, the energy that enters in an initial transient, but unless you can show that nothing happens during the initial transient to deliver some or all of that initial energy to the load, your argument has a hole. You're presupposing that there is some energy that enters the line during an initial transient that cannot leave until you shut the source off, so you get the 100J related to the 100W net power flow and 100J that went into the line before the source knew about the load.. and then there's another 100J that enters somehow? I guess to set up the reflected wave? The argument is circular. The initial transient supplies 200J of stored energy to the line so there must be 300J in a one second line if there's 100J in the steady-state fields associated with power flow. Since there's 300J in the line, the initial transient must have supplied 200J in stored energy. It's just not working for me. Dan |
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wrote:
I've come around to that conservation of energy stuff ;-) I'm glad - most folks here ignore it. :-) I understand that your argument involves the energy that enters the line before it knows anything about the load, the energy that enters in an initial transient, but unless you can show that nothing happens during the initial transient to deliver some or all of that initial energy to the load, your argument has a hole. Let's return to the one second long lossless transmission line. From a 100 watt transmitter, at the end of second number one, the line will contain 100 joules and the load will have accepted zero joules. Since the load is rejecting 1/2 of the incident energy, at the end of the 2nd second, the source will have supplied 200 joules, there will be 150 joules of energy in the line, and 50 joules will have been accepted by the load. If the source is equipped with a circulator+load, this is steady-state with 150 joules of energy stored in the transmission line. At t=0: zero joules zero joules 100w--------one-second long feedline------load rho^2=0.5 Pfor=0-- --Pref=0 Pload=0 At t=1: 100 joules zero joules 100w--------one-second long feedline------load Pfor=100w-- --Pref=0 Pload=0 At t=2: 150 joules 50 joules 100w--------one-second long feedline------load Pfor=100w-- --Pref=50w Pload=50w You're presupposing that there is some energy that enters the line during an initial transient that cannot leave until you shut the source off, so you get the 100J related to the 100W net power flow and 100J that went into the line before the source knew about the load.. and then there's another 100J that enters somehow? I guess to set up the reflected wave? Yes, at the end of the 2nd second, the source has supplied 200 joules and the load has accepted 50 joules. That leaves 150 joules left over that cannot be any place except in the line according to the conservation of energy principle. In a circulator+load system, we have reached steady state with 150 joules in the transmission line that will not reach the load until after the source is powered down. The argument is circular. Proving that confusion exists. It's actually not circular. It's based on cause, effect, and the conservation of energy principle. I apologize if I have not explained it in a way that is easy to understand. Please bear with me. It's all linear cause and effect. With an ideal auto-tuner at the source, none of the reflected energy is accepted back by the source. Half the energy incident upon the load is rejected. There is no other place for the extra energy to be except inside the transmission line. I have an EXCEL spreadsheet that might help you sort all of this out. A copy of its output is available at: http://www.qsl.net/w5dxp/1secsgat.gif -- 73, Cecil http://www.qsl.net/w5dxp |
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Cecil Moore wrote:
I have an EXCEL spreadsheet that might help you sort all of this out. A copy of its output is available at: http://www.qsl.net/w5dxp/1secsgat.gif The EXCEL spreadsheet corresponding to the above can be downloaded from: http://www.qsl.net/w5dxp/1secTline.xls It includes a graph of forward power, reflected power, and joules stored in the transmission line. -- 73, Cecil http://www.qsl.net/w5dxp |
Mismatched Zo Connectors
Cecil Moore wrote:
Cecil Moore wrote: I have an EXCEL spreadsheet that might help you sort all of this out. A copy of its output is available at: http://www.qsl.net/w5dxp/1secsgat.gif The EXCEL spreadsheet corresponding to the above can be downloaded from: http://www.qsl.net/w5dxp/1secTline.xls It includes a graph of forward power, reflected power, and joules stored in the transmission line. I have enhanced that spreadsheet such that the resistive load on the one second long lossless 50 ohm feedline is a variable entered by the user. Please note the graph of forward power, reflected power, and joules stored in the feedline (chart1). The enhanced file is available at: http://www.qsl.net/w5dxp/1secline.xls -- 73, Cecil http://www.qsl.net/w5dxp |
Mismatched Zo Connectors
Cecil,
Have you included the fact that the *source* is properly terminating the line on its end? The source can accept power from the reflected wave, right? Dan |
Mismatched Zo Connectors
wrote:
Have you included the fact that the *source* is properly terminating the line on its end? The source is relying on an ideal autotuner to terminate the line with a 50 ohm Z0-match. The source can accept power from the reflected wave, right? No, there is an ideal autotuner on the output of the source. *Zero reflected energy reaches the source*. The SWR between the Source and the Autotuner is 1:1 just as it is in any properly tuned antenna system. -- 73, Cecil http://www.qsl.net/w5dxp |
Mismatched Zo Connectors
So how are you taking into account the stored energy in the ideal
autotuner? Even if it's perfect, there's energy stored in the fields of the impedance transforming device. Are there 0J in the tuner? If not, how does the impedance transformation take place? Dan |
Mismatched Zo Connectors
Sorry should have been "If so, how does the impedance transformation
take place" not "If not" Dan wrote: Are there 0J in the tuner? If not, how does the impedance transformation take place? Dan |
Error correction
Bart Rowlett wrote:
Reg Edwards wrote: A correction - insert dt instead of dz. Another correction is in order. The resistive term should be i(z) * R and the conductance term should be v(z) * G. The fundamental partial differential equations of transmission lines are - - dv/dz = R + L*di/dt - di/dz = G + C*dv/dt where volts v and current i are incremental functions of distance and time, and z is incremental distance along line. bart Good to know you're still lurking around here, Bart! Glad somebody still keeps track of units. ;-) 73, ac6xg |
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