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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. |
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