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#71
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Keith Dsart wrote:
"Therefore, the forward and reverse waves can not be transferring energy across these points." A wave is defined as a progressive vibrational disturbance propagated through a medium, such as air, without progress or advance of the parts or particles themselves, as in the transmission of sound, light, and an electromagnetic field. Light, for example, is also calld luminous or radiant energy. Sound and radio waves are also examples of energy in motion. Waves in motion are transporting energy no matter how their constituents seem to add at a particular point. Best regards, Richard Harrison, KB5WZI |
#72
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![]() "Yuri Blanarovich" wrote in message ... So you are trying to say that there is standing wave voltage but no standing wave current and therefore no power associated with current??? i am saying that there is standing wave voltage, and standing wave current, but there is no physical sense in multiplying them to calculate a power. hence the concept of standing power waves is meaningless. K3BU found out that when he put 800W into the antenna, the bottom of the coil started to fry the heatshrink tubing, demonstrating more power to be dissipated at the bottom of the coil, proportional to the higher current there, creating more heat and "frying power" (RxI2). This is in perfect right R*I^2 makes perfect sense. you are talking about ONLY the current standing wave which makes perfectly good sense. and the R*I^2 losses associated with it make perfect sense. BUT, resistive losses ARE NOT a result of power in the standing wave, they are resistive lossed resulting from the current. remember the initial assumptions of my analysis, a LOSSLESS line, hence there are not resistive losses. If this requirement is changed then you can start to talk about resistive heating at current maximums and all the havoc that can cause. They seem to be real current and voltage, current heats up resistance, voltage lights up the neons and power is consumed, portion is radiated. The larger the current containing portion, the better antenna efficiency. Where am I wrong? again on the voltage, it is exactly analogous to the current above. voltage waves capacitively coupled to a neon bulb are losses and not covered in my statements. But again note, that type of measurement is measuring the peak voltage of the voltage standing wave, and any power dissipated is sampled from that wave and is not a measure of power in the standing wave. I have a hard time to swallow statement that there is no power in standing wave, when I SAW standing wave's current fry my precious coil and tip burned off with spectacular corona Elmo's fire due to standing wave voltage at the tip. YOU HAVE IT RIGHT! the standing wave current causes heating. the standing wave voltage causes corona. but neither one represents POWER in the standing waves. remember the relationship that must apply within the coax. and can be extended to antennas, though it gets real messy taking into account the radiated part and the change in capacitance and inductance along the length of the radiating elements. P=V^2/Z0=I^2*Z0 now remember that you only have to look at one or the other and at all times the relationship in each wave must obey V=I*Z0. Now consider the infamous shorted coax. at the shorted end the voltage standing wave is always ZERO, by your logic the power would always be zero at that point, but how can that be?? conversly, at a point where the current standing wave is always zero there can be no power in the standing wave, but at that point the voltage is a maximum so would say the power was a maximum... an obvious contradiction. |
#73
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![]() "Dave" wrote in message news:mozbj.844$si6.691@trndny08... "Yuri Blanarovich" wrote in message ... So you are trying to say that there is standing wave voltage but no standing wave current and therefore no power associated with current??? i am saying that there is standing wave voltage, and standing wave current, but there is no physical sense in multiplying them to calculate a power. hence the concept of standing power waves is meaningless. K3BU found out that when he put 800W into the antenna, the bottom of the coil started to fry the heatshrink tubing, demonstrating more power to be dissipated at the bottom of the coil, proportional to the higher current there, creating more heat and "frying power" (RxI2). This is in perfect right R*I^2 makes perfect sense. you are talking about ONLY the current standing wave which makes perfectly good sense. and the R*I^2 losses associated with it make perfect sense. BUT, resistive losses ARE NOT a result of power in the standing wave, they are resistive lossed resulting from the current. remember the initial assumptions of my analysis, a LOSSLESS line, hence there are not resistive losses. If this requirement is changed then you can start to talk about resistive heating at current maximums and all the havoc that can cause. They seem to be real current and voltage, current heats up resistance, voltage lights up the neons and power is consumed, portion is radiated. The larger the current containing portion, the better antenna efficiency. Where am I wrong? again on the voltage, it is exactly analogous to the current above. voltage waves capacitively coupled to a neon bulb are losses and not covered in my statements. But again note, that type of measurement is measuring the peak voltage of the voltage standing wave, and any power dissipated is sampled from that wave and is not a measure of power in the standing wave. I have a hard time to swallow statement that there is no power in standing wave, when I SAW standing wave's current fry my precious coil and tip burned off with spectacular corona Elmo's fire due to standing wave voltage at the tip. YOU HAVE IT RIGHT! the standing wave current causes heating. the standing wave voltage causes corona. but neither one represents POWER in the standing waves. So we have better than perpetual motion case - we can cause heating without consuming power. I better get patent for this before Artsie gets it! There must be some equilibrium somewhere. ....like, there is standing wave current, there standing wave voltage, but no standing wave and no power in it? Richard, wake up your english majorettes and snort it out :-) remember the relationship that must apply within the coax. and can be extended to antennas, though it gets real messy taking into account the radiated part and the change in capacitance and inductance along the length of the radiating elements. P=V^2/Z0=I^2*Z0 now remember that you only have to look at one or the other and at all times the relationship in each wave must obey V=I*Z0. Now consider the infamous shorted coax. at the shorted end the voltage standing wave is always ZERO, by your logic the power would always be zero at that point, but how can that be?? conversly, at a point where the current standing wave is always zero there can be no power in the standing wave, but at that point the voltage is a maximum so would say the power was a maximum... an obvious contradiction. I know one thing, when standing wave current is high, I get loses in the resistance, wires heating up - power being used. When standing wave voltage is high, I get dielectric loses, insulation heats up and melts - power being used, ergo there is a power in standing wave and is demonstrated by certain magnitude of current and voltage at particular distance and P = U x I. I don't know what you are feeding your standing wave antennas, but I am pumping power into them and some IS radiated, some lost in the resistive or dielectric loses. 73 Yuri |
#74
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![]() Evidently, you haven't done enough reading. Yuri is right this time. 73, Tom Donaly, KA6RUH Whoaaaa! When wasn't Yuri right? :-))))) Yuri, da BUm |
#75
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![]() "Yuri Blanarovich" wrote in message ... "Dave" wrote in message news:mozbj.844$si6.691@trndny08... "Yuri Blanarovich" wrote in message ... So you are trying to say that there is standing wave voltage but no standing wave current and therefore no power associated with current??? i am saying that there is standing wave voltage, and standing wave current, but there is no physical sense in multiplying them to calculate a power. hence the concept of standing power waves is meaningless. K3BU found out that when he put 800W into the antenna, the bottom of the coil started to fry the heatshrink tubing, demonstrating more power to be dissipated at the bottom of the coil, proportional to the higher current there, creating more heat and "frying power" (RxI2). This is in perfect right R*I^2 makes perfect sense. you are talking about ONLY the current standing wave which makes perfectly good sense. and the R*I^2 losses associated with it make perfect sense. BUT, resistive losses ARE NOT a result of power in the standing wave, they are resistive lossed resulting from the current. remember the initial assumptions of my analysis, a LOSSLESS line, hence there are not resistive losses. If this requirement is changed then you can start to talk about resistive heating at current maximums and all the havoc that can cause. They seem to be real current and voltage, current heats up resistance, voltage lights up the neons and power is consumed, portion is radiated. The larger the current containing portion, the better antenna efficiency. Where am I wrong? again on the voltage, it is exactly analogous to the current above. voltage waves capacitively coupled to a neon bulb are losses and not covered in my statements. But again note, that type of measurement is measuring the peak voltage of the voltage standing wave, and any power dissipated is sampled from that wave and is not a measure of power in the standing wave. I have a hard time to swallow statement that there is no power in standing wave, when I SAW standing wave's current fry my precious coil and tip burned off with spectacular corona Elmo's fire due to standing wave voltage at the tip. YOU HAVE IT RIGHT! the standing wave current causes heating. the standing wave voltage causes corona. but neither one represents POWER in the standing waves. So we have better than perpetual motion case - we can cause heating without consuming power. I better get patent for this before Artsie gets it! There must be some equilibrium somewhere. ...like, there is standing wave current, there standing wave voltage, but no standing wave and no power in it? Richard, wake up your english majorettes and snort it out :-) remember the relationship that must apply within the coax. and can be extended to antennas, though it gets real messy taking into account the radiated part and the change in capacitance and inductance along the length of the radiating elements. P=V^2/Z0=I^2*Z0 now remember that you only have to look at one or the other and at all times the relationship in each wave must obey V=I*Z0. Now consider the infamous shorted coax. at the shorted end the voltage standing wave is always ZERO, by your logic the power would always be zero at that point, but how can that be?? conversly, at a point where the current standing wave is always zero there can be no power in the standing wave, but at that point the voltage is a maximum so would say the power was a maximum... an obvious contradiction. I know one thing, when standing wave current is high, I get loses in the resistance, wires heating up - power being used. When standing wave voltage is high, I get dielectric loses, insulation heats up and melts - power being used, ergo there is a power in standing wave and is demonstrated by certain magnitude of current and voltage at particular distance and P = U x I. I don't know what you are feeding your standing wave antennas, but I am pumping power into them and some IS radiated, some lost in the resistive or dielectric loses. 73 Yuri you are SO CLOSE... open your eyes, turn off your preconceived notions and read what i wrote again slowly and carefully. FIRST remember the assumption was a LOSSLESS line so there are no dielectric or resistive losses. But this is only useful because it makes it easier to see that the power given by V*I in the standing waves doesn't make sense. YOU ARE CORRECT when you say that the R*I^2 loss is REAL... and YOU ARE CORRECT when you say the V^2/R loss in dielectric is REAL. Where you lose it is that the V*I for the standing waves is not correct... this is because V and I are related to each other and you can't apply superposition to a non-linear relationship. If you think you have a way to do it then please take the given conditions of a lossless transmission line, shorted at the end, in sinusoidal steady state, and write the equation for power in the standing wave at 1/4 and 1/2 a wavelength from the shorted end of the line. |
#76
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#77
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There's been a lot of confusion between average and instantaneous power.
Let me try to clarify a little. Keith Dysart wrote: . . . Now power is really interesting. Recall that P(x,t) = V(x,t) * I(x,t) . . . This is correct. Cecil and others have often muddled things by considering only average power, and by doing this, important information is lost. (As was the case of the statistician who drowned crossing a creek whose average depth was only two feet.) Roger wrote: I would suggest that you add a caveat here. The power equation is true if the measurements are across a resistance. If we are also measuring reactive power (or reflected power), then we need to account for that. And here's where one of the common errors occurs. The fundamental equation given by Keith does "account for" reactive power. If I(t) and V(t) are sinusoidal in quadrature, for example, then V(t) * I(t) is a sinusoidal function (at twice the frequency of V or I), with zero offset. This tells us that for half the time, energy is moving in one direction, and for the other half the time, energy is moving in the opposite direction. The average power is zero, so there is no net movement of energy over an integral number of cycles. This is what is called "reactive power". On the other hand, if V(t) and I(t) are in phase, the product is again a sinusoid with twice the frequency of V or I, but this time with an offset equal to half the peak value of V times the peak value of I. What this tells us is that energy is always moving in the same direction, although its rate (the power) increases and decreases -- clear to zero, in fact, for an instant -- over a cycle. The average power equals this offset. So here the "reactive power" is zero. I've described this as energy "sloshing back and forth", which Cecil has taken great delight in disparaging. But that's exactly what it does, as the fundamental equations clearly show. When V(t) and I(t) are at other relative angles, the result will still be the sinusoid at twice the frequency of V and I, but with an amount of "DC" offset corresponding to the net or average power and therefore the average rate of energy flow. The periodic up and down cycles represent energy moving back and forth around that net value. No additional equation or correction is needed to fully describe the power or the energy flow, or to calculate "real" (average) power or "reactive power". A careful look at what the power and energy are doing on an instantaneous basis is essential to understanding what the energy flow actually is in a transmission line. Attempting to ignore this cyclic movement and looking only at average power can lead to some incorrect conclusions and the necessity to invent non-existent phenomena (such as waves bouncing off each other) in order to hold the flawed theory together. Roy Lewallen, W7EL |
#78
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Roy Lewallen wrote:
... This is correct. Cecil and others have often muddled things by considering only average power, and by doing this, important information is lost. (As was the case of the statistician who drowned crossing a creek whose average depth was only two feet.) ... This: 2. Microwave ovens use standing waves to cook food. This means that nodes, where the amplitude is zero (where the wave crosses the x-axis), remain at nearly fixed locations in the oven, and cooking won't occur at those locations. From he http://faculty.fortlewis.edu/tyler_c..._microwave.htm Now, you can argue that any damn way you wish, but "standing waves of no power" is a myth for idiots! Regards, JS |
#79
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![]() "Dave" wrote in message news:UTAbj.1170$OH6.803@trndny03... "Yuri Blanarovich" wrote in message ... "Dave" wrote in message news:mozbj.844$si6.691@trndny08... "Yuri Blanarovich" wrote in message ... So you are trying to say that there is standing wave voltage but no standing wave current and therefore no power associated with current??? i am saying that there is standing wave voltage, and standing wave current, but there is no physical sense in multiplying them to calculate a power. hence the concept of standing power waves is meaningless. K3BU found out that when he put 800W into the antenna, the bottom of the coil started to fry the heatshrink tubing, demonstrating more power to be dissipated at the bottom of the coil, proportional to the higher current there, creating more heat and "frying power" (RxI2). This is in perfect right R*I^2 makes perfect sense. you are talking about ONLY the current standing wave which makes perfectly good sense. and the R*I^2 losses associated with it make perfect sense. BUT, resistive losses ARE NOT a result of power in the standing wave, they are resistive lossed resulting from the current. remember the initial assumptions of my analysis, a LOSSLESS line, hence there are not resistive losses. If this requirement is changed then you can start to talk about resistive heating at current maximums and all the havoc that can cause. They seem to be real current and voltage, current heats up resistance, voltage lights up the neons and power is consumed, portion is radiated. The larger the current containing portion, the better antenna efficiency. Where am I wrong? again on the voltage, it is exactly analogous to the current above. voltage waves capacitively coupled to a neon bulb are losses and not covered in my statements. But again note, that type of measurement is measuring the peak voltage of the voltage standing wave, and any power dissipated is sampled from that wave and is not a measure of power in the standing wave. I have a hard time to swallow statement that there is no power in standing wave, when I SAW standing wave's current fry my precious coil and tip burned off with spectacular corona Elmo's fire due to standing wave voltage at the tip. YOU HAVE IT RIGHT! the standing wave current causes heating. the standing wave voltage causes corona. but neither one represents POWER in the standing waves. So we have better than perpetual motion case - we can cause heating without consuming power. I better get patent for this before Artsie gets it! There must be some equilibrium somewhere. ...like, there is standing wave current, there standing wave voltage, but no standing wave and no power in it? Richard, wake up your english majorettes and snort it out :-) remember the relationship that must apply within the coax. and can be extended to antennas, though it gets real messy taking into account the radiated part and the change in capacitance and inductance along the length of the radiating elements. P=V^2/Z0=I^2*Z0 now remember that you only have to look at one or the other and at all times the relationship in each wave must obey V=I*Z0. Now consider the infamous shorted coax. at the shorted end the voltage standing wave is always ZERO, by your logic the power would always be zero at that point, but how can that be?? conversly, at a point where the current standing wave is always zero there can be no power in the standing wave, but at that point the voltage is a maximum so would say the power was a maximum... an obvious contradiction. I know one thing, when standing wave current is high, I get loses in the resistance, wires heating up - power being used. When standing wave voltage is high, I get dielectric loses, insulation heats up and melts - power being used, ergo there is a power in standing wave and is demonstrated by certain magnitude of current and voltage at particular distance and P = U x I. I don't know what you are feeding your standing wave antennas, but I am pumping power into them and some IS radiated, some lost in the resistive or dielectric loses. 73 Yuri you are SO CLOSE... open your eyes, turn off your preconceived notions and read what i wrote again slowly and carefully. FIRST remember the assumption was a LOSSLESS line so there are no dielectric or resistive losses. But this is only useful because it makes it easier to see that the power given by V*I in the standing waves doesn't make sense. YOU ARE CORRECT when you say that the R*I^2 loss is REAL... and YOU ARE CORRECT when you say the V^2/R loss in dielectric is REAL. Where you lose it is that the V*I for the standing waves is not correct... this is because V and I are related to each other and you can't apply superposition to a non-linear relationship. If you think you have a way to do it then please take the given conditions of a lossless transmission line, shorted at the end, in sinusoidal steady state, and write the equation for power in the standing wave at 1/4 and 1/2 a wavelength from the shorted end of the line. So let me get this straight: I describe real antenna situation, which is a standing wave circuit, with real heating of the coil, which is consuming power demonstrably proportional to the amount of standing wave current. You are not answering rest of my argument. You bring in lossless transmission line to argue that there can not be power and no standing waves. I still don't get it. 73 Yuri |
#80
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Roger wrote:
What you are forgetting is that power is also found from Power = V^2/Zo and Power = I^2*Zo. More accurately, on the standing wave line, Power = (V^2 + I^2)/Zo. This is why a SWR power meter detects both current and voltage from the standing wave. This will also be true on the quarter wave stub, which is really 1/2 wave length long electrically, when you consider the time required for the wave to go from initiation to end and back to beginning point. Power is stored on the stub during the 1/2 cycle energized, and then that stored power acts to present either a high or low impedance to the next 1/2 cycle, depending upon whether the stub is shorted or open. I think you did a very good job in building your theory. It was only at the end (where I think we need to consider additional ways of measuring power) that we disagree. 73, Roger, W7WKB Haste makes waste, and errors as well. The standing wave power equation is incorrect. It should read "Power = V^2 / Zo + I^2 * Zo" Sorry for any inconvenience, and for the several postings it will probably stimulate. 73, Roger, W7WKB Sorry, neither is correct. Z0 is the ratio of V to I of a traveling wave. It's not the ratio of V to I of the total of a forward and reverse wave (which has been carelessly called "the standing wave" in this thread). If you want to calculate power as V^2 / R or I^2 * R, you have to use Re(V/I) as the value of R -- then you will, as you must, get the same result using V * I, I^2 * R, or V^2 / R. As any text can tell you, the value of Z (ratio of V to I) varies along a line which has reflected waves (i.e., has a standing wave). If you use Z0 for the calculation in those cases, you get results which have no meaning or physical significance. V^2 / R + I^2 * R doesn't give power, using either Z0 or V/I as R. I'm curious as to where that equation came from or how it was derived. Roy Lewallen, W7EL |
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