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Current across the antenna loading coil - from scratch
Cecil Moore wrote:
John Popelish wrote: Cecil Moore wrote: http://www.qsl.net/w5dxp/travstnd.GIF Agreed, with one exception. There is a phase reversal each time you pass through a node, ... You are correct if two sides of a node exist in the system. But since the context was my above 1/4WL wire, there is no "passing through a node". I was limiting my statements in context to a 1/4WL long conductor. So, add some transmission line to the system so a node's location is measurable inside the system. By the way, in case you didn't notice, I am agreeing with you, and elaborating on what you are saying. |
Current across the antenna loading coil - from scratch
200W-- 2 amps--
hole-------------------50 ohm coax-------------------hole --200W --2 amps which direction is that current flowing? As usual, the question is nonsense when the picture reveals the answer. Cecil rarely sees the irony - except to brush it off as 1. Rhetoric (no answer needed, an admission of wasting time); 2. Our error for not knowing he made a squinty-eyed mistake (playing the pity card); 3. A joke (having forgotten one of a bajillion happy faces). The real joke follows below. ;-) (my own happy face) On Sat, 08 Apr 2006 12:54:05 -0400, John Popelish wrote: If the source were known to be to the left, would that change your answer? For a pure standing wave, there is effectively a source at each end, so this question is meaningless. Hi John, That was a good joke too, mine is different. ************** spoiler follows ************** The current is flowing in the SWR meter. DUH! I would, of course, task any/everyone to find any point along the line where the SWR meter does not exhibit current flow for this configuration. :-) Quod Erat Demonstrandum Of course, armchair theories based upon Xeroxed research of third parties (which necessarily implies the Xeroxing assignment did not include copying that significant page which decimates their argument) may now rattle on. 73's Richard Clark, KB7QHC |
Current across the antenna loading coil - from scratch
John Popelish wrote:
See all those arrows of various length representing current direction and magnitude? Why do you ask me about something after erasing my answer? As is my custom, I erase everything I agree with. If the source were known to be to the left, would that change your answer? For a pure standing wave, there is effectively a source at each end, so this question is meaningless. Exactly! Now try to tell that to W8JI and W7EL who attempt to assign a direction of flow to standing wave current and use its phase to determine the phase shift through a wire or coil. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
John Popelish wrote:
So, add some transmission line to the system so a node's location is measurable inside the system. By the way, in case you didn't notice, I am agreeing with you, and elaborating on what you are saying. I know you are agreeing with me. The only disagreement you and I have ever had was over my poor choice of words. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Cecil Moore wrote: 200W-- 2 amps-- hole-------------------50 ohm coax-------------------hole --200W --2 amps Which direction is the standing wave current flowing? What are you calling "standing wave current flow"? Describe or define it. Are you actually saying charges flow two directions at the same time and place in any given snapshot of time? The current we would measure at any place with a current indicator and the phase of that current IS the actual current flow. Any solution breaking it down into forward and reflected current has to produce the same answer as the measurement, and that current (as you agreed earlier) is the current responsible for radiation, heating, and phase of the radiated field. It is impossible to have different currents at each end of the inductor without having displacement currents, or what Reg calls "radial current flow". Why are you complicating your life with something that seems to be giving you the wrong answer? More important, why do you want the rest of the world to share in having the wrong answer? 73, Tom |
Current across the antenna loading coil - from scratch
On Sat, 08 Apr 2006 18:08:37 GMT, Cecil Moore
wrote: an SWR meter is not 100% dependent upon a current flow reading, eh? ********** W R O N G !! ************* No meter movement moves without current! Ta Dah! more rattling of dusty bones about Zero (0) current may now continue.... |
Current across the antenna loading coil - from scratch
Cecil Moore wrote: Water waves flow two directions at the same time using the same water molecules. And any one of those molecules that participate in the process move in a circular motion, if the process is a pure traveling wave, or up and down if the process is a pure standing wave. EM waves flow two directions at the same time using the same carriers. Charge movement. Waves in a rope travel two directions at the same time using the same molecules. It is a common physical occurrence. Hint: The carriers of the waves are NOT the same thing as the waves. The current we would measure at any place with a current indicator and the phase of that current IS the actual current flow. What direction is that current flowing when its phase is not changing relative to the source phase? This is a key question. The current in the wire must be in one of two directions, since that is the only path the wire can provide. However, there are also radial displacements driven by the rate of change of voltage at each point along the wire. The displacement currents are what allow the current in the wire to be different at different points. If there were no dosplacement curents, the speed of light would be infinite and there would be no waves. It is impossible to have different currents at each end of the inductor without having displacement currents, or what Reg calls "radial current flow". We have different currents at each end of a wire quite often without having displacement currents. Impossible. Any conductor with changing voltage has displacement current to ite surroundings. Does having zero amps and one point and one amp 1/4WL away mean there's displacement current in a transmission line? If there is non zero amps nearby, that is exactly what it means. When you figure out the answer to that one, you will understand why the coil can have negligible displacement current and still have zero amps at one end and one amp at the other end, just like the wire or transmission line. You cannot have a transmission line without displacement currents. Source--------------a-/////////-b------------------------------- Measured current at 'a' is zero amps. Measured current at 'b' is one amp. Where is the current at 'b' coming from? Certainly NOT from displacement currents. I disagree. every conductive surface with varying voltage on it has displacement curent, whether that surface is part of a transmission line, a coil, or an antenna. Why are you complicating your life with something that seems to be giving you the wrong answer? Actually, I am complicating your life with something that gives the correct answer. If you will fix your misconceptions about standing wave current, everything else should be just fine. You can have no waves in transmission lines, coils or antennas without displacement currents. They are half of what supports the waves and determines their speed. |
Current across the antenna loading coil - from scratch
Richard Clark wrote:
Cecil Moore wrote: an SWR meter is not 100% dependent upon a current flow reading, eh? ********** W R O N G !! ************* No meter movement moves without current! Who said anything about the meter movement? We are talking about the RF current magnitude which indeed can be zero. When the RF standing wave current magnitude is zero, it just means that all the energy is stored in the standing wave voltage which is half of the SWR measurement. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Richard Clark wrote:
On Sat, 08 Apr 2006 12:54:05 -0400, John Popelish wrote: For a pure standing wave, there is effectively a source at each end, so this question is meaningless. Hi John, That was a good joke too, mine is different. (snip) I was not trying to be humorous. I was stating a fact as I understand it. |
Current across the antenna loading coil - from scratch
Cecil Moore wrote:
John Popelish wrote: See all those arrows of various length representing current direction and magnitude? Why do you ask me about something after erasing my answer? As is my custom, I erase everything I agree with. If the source were known to be to the left, would that change your answer? For a pure standing wave, there is effectively a source at each end, so this question is meaningless. Exactly! Now try to tell that to W8JI and W7EL who attempt to assign a direction of flow to standing wave current and use its phase to determine the phase shift through a wire or coil. Not my job. |
Current across the antenna loading coil - from scratch
Cecil Moore wrote:
John Popelish wrote: So, add some transmission line to the system so a node's location is measurable inside the system. By the way, in case you didn't notice, I am agreeing with you, and elaborating on what you are saying. I know you are agreeing with me. The only disagreement you and I have ever had was over my poor choice of words. Read on. I just posted something that disagrees with you about something fundamental. I have no intention of bucking you or supporting you. I am interested in understanding. |
Current across the antenna loading coil - from scratch
wrote:
The current in the wire must be in one of two directions, since that is the only path the wire can provide. In which direction is that current flowing when its phase is unchanging with respect to the source? Any conductor with changing voltage has displacement current to ite surroundings. Which are quite often negligible compared to the effect of the phasor addition of forward and reflected currents. All I am saying is that the displacement current to ground is often a secondary effect which can be ignored when only primary effects are being considered. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
On Sat, 08 Apr 2006 20:30:32 GMT, Cecil Moore
wrote: Richard Clark wrote: Cecil Moore wrote: an SWR meter Who said anything about the meter movement? Ta Dah! No current, no SWR indication. |
Current across the antenna loading coil - from scratch
On Sat, 08 Apr 2006 10:21:08 -0700, Richard Clark
wrote: As usual, the question is nonsense when the picture reveals the answer. Cecil rarely sees the irony - except to brush it off as 1. Rhetoric (no answer needed, an admission of wasting time); 2. Our error for not knowing he made a squinty-eyed mistake (playing the pity card); 3. A joke (having forgotten one of a bajillion happy faces); 4. His poor choice of words (playing the pity card - 3 of Hearts); Always room for one more excuse (to be continued). The challenge continues without upset or serious contest: The current is flowing in the SWR meter. DUH! I would, of course, task any/everyone to find any point along the line where the SWR meter does not exhibit current flow for this configuration. :-) Quod Erat Demonstrandum 73's Richard Clark, KB7QHC |
Current across the antenna loading coil - from scratch
Richard Clark wrote:
"No current, no SWR." That exact spot producing an SWR induced voltage cancellation must also have double the voltage of either the forward or reverse wave. Voltage maxima are concurrent with current minima. Your SWR meter needs to be able to give a good indication at any spot in the line including all maxima and minima. Best regards, Richard Harrison, KB5WZI |
Current across the antenna loading coil - from scratch
Richard Harrison wrote:
Richard Clark wrote: "No current, no SWR." That exact spot producing an SWR induced voltage cancellation must also have double the voltage of either the forward or reverse wave. Voltage maxima are concurrent with current minima. Your SWR meter needs to be able to give a good indication at any spot in the line including all maxima and minima. Yes, what happens if the current sample is zero is that the forward power indication and reflected power indication are the same and indeed Vv - Vi = Vv + Vi = Vv. The indicated forward power and reflected power are equal just as they should be. But the trivial point that Richard C. was making is that the meter movement requires current - true but completely irrelevant. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Cecil Moore wrote: Are you actually saying charges flow two directions at the same time and place in any given snapshot of time? Cecil wrote: Water waves flow two directions at the same time using the same water molecules. EM waves flow two directions at the same time using the same carriers. Waves in a rope travel two directions at the same time using the same molecules. It is a common physical occurrence. Hint: The carriers of the waves are NOT the same thing as the waves. Current is by definition is the flow of charge. A current of one coulomb per second is one ampere. By definition and by physics, we cannot have charges flowing two directions at once at one point. Even if we had some strange mechanism in the conductor allowing this, radiation and the phase of EM fields would be determined by the net charge movement. This is precisely the current we would measure with a current meter sampling the magnetic field, it is the current we would measure sampling radiation, and it is the current that would determine phase of the radiation or induction field. So please expain to use, even if we allow a conductor to have TWO voltage gradients of opposite polarity over the same linear area of conductor, why Cecil's Current is important. Also, tell us how we can measure and prove in a repeatable test, the two-way charge movement exists. The current we would measure at any place with a current indicator and the phase of that current IS the actual current flow. What direction is that current flowing when its phase is not changing relative to the source phase? This is a key question. Either you are creating diversionary conundrums, or you should be able to explain how we can have charges moving past a point in a single conductor that are moving both directions at one instant of time. Tell us how that happens. Tell us why we suddenly cannot use drift velocity to calculate current, or current to calculate drift velocity. The almost universal measurement method of current is magnetic. Suddenly Cecil's Theory of Current renders universal measurement methods obsolete! NEC uses current and voltage, not wave theory. You attempt to use an engine that uses what you say we can use to prove we are wrong in using current when there are standing waves! Don't you think you should have understood the NEC engine used in the program before using it to prove we cannot use current without reflections? Eznec uses the very same thing we can measure with a clamp on meter, so it appears you are the one who is doing something wrong. It is impossible to have different currents at each end of the inductor without having displacement currents, or what Reg calls "radial current flow". We have different currents at each end of a wire quite often without having displacement currents. Does having zero amps and one point and one amp 1/4WL away mean there's displacement current in a transmission line? Yes, absolutely. If you don't understand that, you'd better review basic transmission lines and quit wasting everyone else's time giving assignments. When you figure out the answer to that one, you will understand why the coil can have negligible displacement current and still have zero amps at one end and one amp at the other end, just like the wire or transmission line. Nonsense Cecil. I'd wager almost everyone here understands transmission lines better than that! It appears you have wandered off into the land of reflections without also understanding basic circuits. The transmission line can be represented as a network of series inductors and shunt capacitors, just as an antenna (even a single conductor) in space can. The only reason current changes is displacement currents (the electric field) allow current to decrease by providing the third path. If we stopped that third path, the current would not change. We can analyze any stub with EXACTLY the same results wave theory produces. Other than imperfect precision in both methods, the results are the same. The minute any of us start thinking there is only one model, either circuit or wave theory, that works and we cannot fit the other method with the same results, it shows something is wrong. Your model, if you rule out displacement currents, cannot work. Your model, if it requires net current flow that does not register as a magnetic induction field or as a thermal effect, and if the radiation phase and level is not tied to the same ampere-feet we measure with conventional instrumentation, is a fantasy. Go back to what makes charges move, and explian how thay can move two directions at the same time in a very small crossection of conductor in terms of the wavelength. Answer the question Cecil, how can we have charge movement over a small length of conductor (in terms of the wavelength) in two directions at the same time, or a drift velocity in two directions at once? 73 Tom |
Current across the antenna loading coil - from scratch
Richard Clark wrote:
********** W R O N G !! ************* No meter movement moves without current! Ta Dah! Richard is wrong too! There are electrostatic meter movements. 73, Roger -- Remove tilde (~) to reply Remember the USS Liberty (AGTR-5) http://ussliberty.org/ |
Current across the antenna loading coil - from scratch
Cecil Moore wrote:
wrote: The current in the wire must be in one of two directions, since that is the only path the wire can provide. In which direction is that current flowing when its phase is unchanging with respect to the source? At any point along the wire, and at any particular instant, whether as a result of a standing or traveling wave, the current flows in the direction of the wire, one way or the other. Such current does not have a phase. It has a direction. The sinusoidal cycle of variation through time is what has a phase with respect to some reference. The cycle of current in a standing wave, at any point has one of only two phases. There is also a current at any point that passes between the surface of the wire and the surroundings (capacitive current), but you don't generally measure or describe that current when dealing with antenna elements, transmission lines or coils. You generally quantify only the current in the direction of the wire. But it is the displacement current radial to the wire that is responsible for all variation of current (magnitude and phase) along a conductor. Any conductor with changing voltage has displacement current to ite surroundings. Which are quite often negligible compared to the effect of the phasor addition of forward and reflected currents. Those wave currents could not travel at nearly the speed of light without the displacement currents. They are what set the wave velocity (in conjunction with the inductance per length). They can never be forgotten when dealing with waves. They allow waves to happen. All I am saying is that the displacement current to ground is often a secondary effect which can be ignored when only primary effects are being considered. Then you are silly. You cannot describe the reason for wave velocity of a conductor, transmission line or EM wave without displacement current. It would like trying to describe water surface waves without referring to the density of water. For instance, when there is a standing wave current node, and current is toward that node (charge is piling up), from both sides, where do you think it is going? There is only one place. Displacement current into the space around the node. And at the node where current is instantaneously heading from the node, in both directions (that is what 180 degrees across the node means), simultaneously, there is only one place it can come from. Displacement current from the space around that node. If you superimpose the graph of standing wave voltage along the line with the graph of standing wave current, you will see that the voltage wave has its peaks at the current nodes, and it is this large voltage swing that is driving the peak displacement current at those points. So please stop saying that displacement current is negligible in some cases of traveling or standing waves. It is a silly thing to say. |
Current across the antenna loading coil - from scratch
On Sat, 08 Apr 2006 20:19:13 -0400, Roger D Johnson
wrote: Richard is wrong too! There are electrostatic meter movements. ********** W R O N G !! ************* Ah! Fresh Meat. Explain how that movement moves with a charge moving (current!). Ta Dah! |
Current across the antenna loading coil - from scratch
On Sat, 08 Apr 2006 22:53:39 GMT, Cecil Moore
wrote: movement requires current - true but completely irrelevant. Ta Dah! the myth of zero (0) current is busted. |
Current across the antenna loading coil - from scratch
On Sat, 08 Apr 2006 15:30:12 -0700, Richard Clark
wrote: On Sat, 08 Apr 2006 10:21:08 -0700, Richard Clark wrote: As usual, the question is nonsense when the picture reveals the answer. Cecil rarely sees the irony - except to brush it off as 1. Rhetoric (no answer needed, an admission of wasting time); 2. Our error for not knowing he made a squinty-eyed mistake (playing the pity card); 3. A joke (having forgotten one of a bajillion happy faces); 4. His poor choice of words (playing the pity card - 3 of Hearts); 5. true but completely irrelevant (the stupid card); Always room for one more excuse (to be continued). The challenge continues without upset or serious contest: The current is flowing in the SWR meter. DUH! I would, of course, task any/everyone to find any point along the line where the SWR meter does not exhibit current flow for this configuration. :-) Quod Erat Demonstrandum 73's Richard Clark, KB7QHC |
Current across the antenna loading coil - from scratch
Richard Clark wrote:
On Sat, 08 Apr 2006 20:19:13 -0400, Roger D Johnson wrote: Richard is wrong too! There are electrostatic meter movements. ********** W R O N G !! ************* Ah! Fresh Meat. Explain how that movement moves with a charge moving (current!). Perpetual motion? ;^) - 73 de Mike KB3EIA - |
Current across the antenna loading coil - from scratch
Roger D Johnson wrote: Richard is wrong too! There are electrostatic meter movements. 73, Roger Roger is wrong too, and Richard is not. Electrostatic indicators don't measure current or charge movement, they measure voltage or charge displacement. But what I really want to know is how Cecil can have current flowing both directions at the same instant of time in a single point of single conductor, can dismiss displacement currents as trivial things that can be ignored when they are required to define the most important aspects of transmission or antenna behavior, and say the very thing that is used to measure current suddenly doesn't measure his imaginary two-way reflected and forward current's vector sum. That's what is really important, especially in light of the fact Cecil is quick to play superior. Anyone who is really superior should be able to walk us through the physics of two-way current and tell us why dosplacement currents don't matter, and explain his magical transmission lines and antennas without displacement current in a way that we all understand. 73 Tom |
Current across the antenna loading coil - from scratch
On Sat, 08 Apr 2006 21:32:20 -0400, Mike Coslo
wrote: Richard Clark wrote: On Sat, 08 Apr 2006 20:19:13 -0400, Roger D Johnson wrote: Richard is wrong too! There are electrostatic meter movements. ********** W R O N G !! ************* Ah! Fresh Meat. Explain how that movement moves with a charge moving (current!). Perpetual motion? ;^) It only takes a moment, and a millimeter - Only Cecil could make that perpetual. |
Current across the antenna loading coil - from scratch
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Current across the antenna loading coil - from scratch
Richard Clark wrote:
On Sat, 08 Apr 2006 20:19:13 -0400, Roger D Johnson wrote: Richard is wrong too! There are electrostatic meter movements. ********** W R O N G !! ************* Ah! Fresh Meat. Explain how that movement moves with a charge moving (current!). Ta Dah! I don't understand your statement. Explanation he http://www.tpub.com/neets/book3/7k.htm 73, Roger -- Remove tilde (~) to reply Remember the USS Liberty (AGTR-5) http://ussliberty.org/ |
Current across the antenna loading coil - from scratch
|
Current across the antenna loading coil - from scratch
wrote:
Current is by definition is the flow of charge. And two equal EM waves flowing in opposite directions in the same wire use the same charge carriers. By definition and by physics, we cannot have charges flowing two directions at once at one point. A charge carrier cannot be moving in two directions at the same time. Two currents can certainly exist in opposite directions at the same time. That's what forward current and reflected current is. If you want to deny the existence of forward and reflected current, be my guest. This is precisely the current we would measure with a current meter sampling the magnetic field, it is the current we would measure sampling radiation, and it is the current that would determine phase of the radiation or induction field. Yes, but if it's phase is unchanging, which direction is it flowing? When the forward current and reflected current are of equal magnitudes, which direction is the phasor sum of those two currents flowing? So please expain to use, even if we allow a conductor to have TWO voltage gradients of opposite polarity over the same linear area of conductor, why Cecil's Current is important. I have told you and W7EL about a dozen times before. One cannot use standing wave current phase to measure the phase shift through a wire or through a coil. Any such attempt will fail. Yet, that is what W7EL has reported as technical fact for about a year now. Also, tell us how we can measure and prove in a repeatable test, the two-way charge movement exists. Please stop implying something that isn't true. There is no two-way movement of single charge carriers. The current is NOT the same thing as the charge carriers. Either you are creating diversionary conundrums, or you should be able to explain how we can have charges moving past a point in a single conductor that are moving both directions at one instant of time. Please cut the BS, Tom. Individual charge carriers don't move in both directions at the same time. The forward and reflected current waves move in both directions at the same time, unaware of each other's presence until they encounter an impedance discontinuity. It is obvious that you don't understand forward and reflected EM waves that can exist on a wire or even in free space. Please crack open a textbook on such. Ramo and Whinnery is a good reference. The almost universal measurement method of current is magnetic. Suddenly Cecil's Theory of Current renders universal measurement methods obsolete! This is technical discussion and has absolutely nothing to do with you or me. NEC uses current and voltage, not wave theory. You attempt to use an engine that uses what you say we can use to prove we are wrong in using current when there are standing waves! How do you explain EZNEC getting the same answer as the distributed network model at: http://www.qsl.net/w5dxp/travstnd.GIF? And while you are looking at that graph, please explain how the flat phase of the standing wave current can be used to measure phase through a wire or a coil. Don't you think you should have understood the NEC engine used in the program before using it to prove we cannot use current without reflections? No. EZNEC agrees with the distributed network model. That's all I need to know about it. Yes, absolutely. If you don't understand that, you'd better review basic transmission lines and quit wasting everyone else's time giving assignments. Exactly how does the displacement current to ground get outside of a coax line with no common-mode currents? If we stopped that third path, the current would not change. Assume one amp of forward current and one amp of reflected current inside a piece of coax with no common-mode current. There's no third path to ground, yet the standing wave still exists, with current nodes and current loops. No third path to ground is required. Answer the question Cecil, how can we have charge movement over a small length of conductor (in terms of the wavelength) in two directions at the same time, or a drift velocity in two directions at once? Your straw man is noted for all the world to see. A single charge carrier cannot move in two directions at the same time. But if you are denying that two EM waves can move in opposite directions at the same time, please just come right out and assert such. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
John Popelish wrote:
At any point along the wire, and at any particular instant, whether as a result of a standing or traveling wave, the current flows in the direction of the wire, one way or the other. Such current does not have a phase. It has a direction. In what direction is the RMS value of standing wave current flowing? Those wave currents could not travel at nearly the speed of light without the displacement currents. You and I are talking about different displacement currents. I'm talking about displacement current between a transmission line and the ground. We had previously been talking about displacement current between a loading coil and ground. Then you are silly. You cannot describe the reason for wave velocity of a conductor, transmission line or EM wave without displacement current. How does the displacement current get to ground when it's inside a shielded piece of coax with no common mode current on the outside braid? Displacement current into the space around the node. How does the displacement current get past the coax shield to the outside world? So please stop saying that displacement current is negligible in some cases of traveling or standing waves. I'll even say it again. Inside a piece of shielded coax, the displacement current to ground is negligible yet the standing wave still exists. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Richard Clark wrote:
Cecil Moore wrote: movement requires current - true but completely irrelevant. the myth of zero (0) current is busted. Please tell us about the position and velocity of each charge carrier, Richard. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Cecil Moore wrote:
wrote: Current is by definition is the flow of charge. And two equal EM waves flowing in opposite directions in the same wire use the same charge carriers. At points where those waves cause equal and opposite instantaneous current, the standing wave current hits zero (is at a node). At all other points, there is some net instantaneous current that is the superposition of the current caused by the two waves at that point and moment in time. By definition and by physics, we cannot have charges flowing two directions at once at one point. A charge carrier cannot be moving in two directions at the same time. Two currents can certainly exist in opposite directions at the same time. No. Current is the rate of charge movement. The charge cannot be moving two directions at a point. That's what forward current and reflected current is. Those are forward and reverse waves, not forward and reverse currents. you are confusing the wave with the water. If you want to deny the existence of forward and reflected current, be my guest. I deny it. There is only current at a point, just as there is only water jiggling around under a wave on the ocean. This is precisely the current we would measure with a current meter sampling the magnetic field, it is the current we would measure sampling radiation, and it is the current that would determine phase of the radiation or induction field. Yes, but if it's phase is unchanging, which direction is it flowing? Phase doesn't indicate the direction charge is flowing (current is going). For both traveling waves and standing waves, charge sloshes back and forth with no average movement over a cycle. The phase of that movement just tells you how that sloshing is timed with respect to the phase reference. The only case where charge moves in one direction (unidirectional current) is DC. When the forward current and reflected current are of equal magnitudes, which direction is the phasor sum of those two currents flowing? As long as you refer to waves as current, you are never going to get it. Waves travel on current reversals, but he wave is not current. (snip repetition) |
Current across the antenna loading coil - from scratch
wrote:
But what I really want to know is how Cecil can have current flowing both directions at the same instant of time in a single point of single conductor, Forward and reflected EM waves, of course. Would you like to deny the existence of the two waves in the following equation? I(x,t) = I1*cos(kx+wt) + I2*cos(kx-wt) = Io*cos(kx)*cos(wt) Your lack of math skills is really getting to be embarassing. ... can dismiss displacement currents as trivial things that can be ignored when they are required to define the most important aspects of transmission or antenna behavior, The only displacement currents that I said were secondary were the displacement currents to ground. In fact, in a shielded coax with no common mode current, displacement currents to ground are literally non-existent, yet the standing wave is still there inside the coax, with its nodes and loops. ... and say the very thing that is used to measure current suddenly doesn't measure his imaginary two-way reflected and forward current's vector sum. I didn't say that. I said the standing wave phase cannot be used to measure the phase through a wire or a coil. That is readily apparent at: http://www.qsl.net/w5dxp/travstnd.GIF which you have been avoiding like the plague. The phase information is there in the standing wave current, but it is in the magnitude, not the phase. And you have to understand arc-cosine functions to be able to extract that phase information. That's what is really important, especially in light of the fact Cecil is quick to play superior. "Play superior"??? I'm not the arrogant one claiming to be so omniscient that he is never wrong. Anyone who is really superior should be able to walk us through the physics of two-way current ... Already done - please reference the above web page. All the data is exactly what EZNEC reported. I can lead you to water but I can't make you drink. If you will tell me what you don't understand about that web page, I will walk you through it, step by step. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Tom Ring wrote:
wrote: Answer the question Cecil, how can we have charge movement over a small length of conductor (in terms of the wavelength) in two directions at the same time, or a drift velocity in two directions at once? Cecil and Co. are not interested in real physics, math, or engineering. They have made up their own. As I said to Roy, you may as well give up. Tom, I learned this stuff at Texas A&M in the 50's and it was decades old already, having been developed before I was born. Are you also willing to deny the existence of simultaneous forward and reflected EM waves? -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
On Sat, 08 Apr 2006 22:20:10 -0400, Roger D Johnson
wrote: I don't understand your statement. Explanation he http://www.tpub.com/neets/book3/7k.htm Hi Roger, Yes, I understood. And from your reference: "The electrostatic meter movement is actually a large variable capacitor in which one set of plates is allowed to move. The movement of the plates is opposed by a spring attached to the plates. A pointer that indicates the value of the voltage is attached to these movable plates. As the voltage increases, the plates develop more torque." When a current is applied to a capacitor (aka voltage applied, but as we all know, a current moves charge to those plates), there is a force developed between the plates (actually in the dielectric) which is tangential to the plates. This force has the tendency to eject the dielectric. Our usual experience with capacitors is we rarely have enough charge AND enough capacitance to measure this effect. By making one plate movable, the force of the current flow is expressed in the movement of that plate against a spring (the exact analogue of opposing magnetic fields, one fixed and the other imparted by a continuous current flow). "To develop sufficient torque, the plates must be large and closely spaced." That necessary condition of high capacitance; and " A very high voltage is necessary to provide movement, therefore, electrostatic voltmeters are used only for HIGH VOLTAGE measurement." enough charge to reveal the force. Your reference is actually ********** W R O N G !! or at least incomplete ************* because what it is describing with two plates in repulsion is NOT a capacitor (at least not in the conventional sense). This is because the two plates share the same charge (because they are the same conductor), hence the repulsion. Further, as this is a variant on the Leyden Jar, there is another true capacitive plate either in the nearby structure, or the earth. Otherwise there is no reason for the charge to flow there in the first place. 73's Dr. Science (actually, he only has a B.A. in English) |
Current across the antenna loading coil - from scratch
Tom Donaly wrote:
Cecil can't prove that charge can move in two opposite directions at once. No one can. It's impossible. I agree with you. That topic is just another straw man from W8JI who is afraid to discuss EM waves moving in opposite directions at the same time. It's the EM waves that are moving in opposite directions at the same time, not the individual charge carriers. I have seen waves flowing in and flowing out at the same time in the Pacific Ocean. That doesn't mean that individual water molecules are moving in two opposite directions at once. Doesn't it mean you are losing the argument when you have to make up false stories about what I have said? -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Cecil Moore wrote:
John Popelish wrote: At any point along the wire, and at any particular instant, whether as a result of a standing or traveling wave, the current flows in the direction of the wire, one way or the other. Such current does not have a phase. It has a direction. In what direction is the RMS value of standing wave current flowing? That's easy. RMS current is an AC measurement of current along the conductor. Over any integer number of cycles, the total movement of charge is zero. The current spends half the time going one way, and half the time going the other way. This applies to both standing and traveling wave induced currents. The only current that describes a net movement of charge in a single direction is DC. Those wave currents could not travel at nearly the speed of light without the displacement currents. You and I are talking about different displacement currents. I'm talking about displacement current between a transmission line and the ground. If the transmission line is a center conductor in a grounded shield, then that is what I am talking about. If the transmission line is balanced, then the displacement current is mostly the current between the two lines. We had previously been talking about displacement current between a loading coil and ground. That's also included in what I am talking about. Ant current caused by a voltage swing in a conductive surface along the wave path is included. Then you are silly. You cannot describe the reason for wave velocity of a conductor, transmission line or EM wave without displacement current. How does the displacement current get to ground when it's inside a shielded piece of coax with no common mode current on the outside braid? The shield is the ground potential for the center conductor. If you could mount a tiny current pickup loop between the center conductor and shield, surrounding nothing but the coax dielectric (so you could look through the hole, if you were an observer on the center conductor), that pickup loop would measure a current if there is any voltage wave on the center conductor. That is a displacement current. Displacement current into the space around the node. How does the displacement current get past the coax shield to the outside world? As far as the center conductor is concerned, the shield is the entire universe. So please stop saying that displacement current is negligible in some cases of traveling or standing waves. I'll even say it again. Inside a piece of shielded coax, the displacement current to ground is negligible yet the standing wave still exists. You have a blind spot as to where there is current in a coax. Do you deny current through any other capacitor that has voltage swing across it? Then why deny that the capacitance between the center conductor and a carefully surrounding grounded surface separated by a dielectric conducts current when there is voltage swing on the center conductor? If the coax carries a standing wave, then at the points on the center conductor that are current nodes (for current along the conductor) the capacitive current to the shield is at its peak, because that is where the voltage peaks of the standing wave occur. |
Current across the antenna loading coil - from scratch
Cecil Moore wrote:
wrote: But what I really want to know is how Cecil can have current flowing both directions at the same instant of time in a single point of single conductor, Forward and reflected EM waves, of course. Would you like to deny the existence of the two waves in the following equation? I(x,t) = I1*cos(kx+wt) + I2*cos(kx-wt) = Io*cos(kx)*cos(wt) Those two expressions describe patterns of current over time and location that produce current in each direction half the time (except at nodes, where the current is zero). The amplitude of a current cycle is constant for the first one (traveling wave), but the phase differs at different locations (by the amount of kx). The amplitude of current cycle described by the second one (traveling wave) varies with location, and the phase has only two possibilities (one when cos(kx) is positive and 180 degrees different when cos(kx) is negative). But in both cases, current at any point reverses twice a cycle (cos(wt)) and charge goes nowhere over a cycle. |
Current across the antenna loading coil - from scratch
Yuri wrote:
You agree that impedance along the radiator changes, being low at the bottom, around tens of ohms, to being high at the top, around thousands of ohms. )Tom replied: )I never said that. What do you mean by reactance? The X can be very )high but radiation resistance very low even near the open end. I really give up. What's the point. This is a typical example of Tom's response to technical argument or trying to go step by step. I am talking impedance, he "knows" I mean reactance. As I said, I get better response from a brick wall. No wonder he duntgetit! Oh well! 73, Yuri, K3BU |
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