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its raining, its going to rain all weekend, i already caught up my qsl card
replies, what can i do for fun this weekend... I know, troll a fight on r.r.a.a! How about it you guys, you up for a return bout of lumps vs distributions? how about adding powers, that one hasn't come up recently?? maybe a quick argument over why kirchoff's current equation doesn't work with distributed systems?? Or could we drum up a good fight about fractal-quad-yagi efficiency, or how cfa's can't work the way they are claimed to? Come on, there must be a good one in there somewhere to get you guys stirred up for a weekend! Who wants to be the first one to tell me i can't use 75 ohm hardline without some fancy matching system?? Or why my SWR meter is no good when i do? Come on, just a little fight??? |
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SWR METERS ONLY INDICATE FORWARD CW POWER AND REVERSE CB JARGON INTO
THE CROSSED-FIELD FRAKTAL YAGI IF THE IMPEDANCE OF THE SLOW-WAVE LOADING COIL TRANSMISSION LINE IS EXACTLY 49.0003000+j3.50003000 OHMS PLUS OR MINUS 39%! 73, Dan N3OX |
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ALL RIGHT! thats the kind of assertion that should stir things up. I like
the 'slow-wave' part, thats a good one... maybe we should compare it to one of those faster than light antennas in the patent archives and see if we can get something going? wrote in message oups.com... SWR METERS ONLY INDICATE FORWARD CW POWER AND REVERSE CB JARGON INTO THE CROSSED-FIELD FRAKTAL YAGI IF THE IMPEDANCE OF THE SLOW-WAVE LOADING COIL TRANSMISSION LINE IS EXACTLY 49.0003000+j3.50003000 OHMS PLUS OR MINUS 39%! 73, Dan N3OX |
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Dave wrote:
ALL RIGHT! thats the kind of assertion that should stir things up. I like the 'slow-wave' part, thats a good one... maybe we should compare it to one of those faster than light antennas in the patent archives and see if we can get something going? How about a loss of de-Corum...... ;^) Sorry Cecil, I'm a sucker for a bad pun! - 73 de Mike KB3EIA - |
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"Dave" wrote in message . .. its raining, its going to rain all weekend, i already caught up my qsl card replies, what can i do for fun this weekend... I know, troll a fight on r.r.a.a! How about it you guys, you up for a return bout of lumps vs distributions? how about adding powers, that one hasn't come up recently?? maybe a quick argument over why kirchoff's current equation doesn't work with distributed systems?? Or could we drum up a good fight about fractal-quad-yagi efficiency, or how cfa's can't work the way they are claimed to? Come on, there must be a good one in there somewhere to get you guys stirred up for a weekend! Who wants to be the first one to tell me i can't use 75 ohm hardline without some fancy matching system?? Or why my SWR meter is no good when i do? Come on, just a little fight??? Weekend fight promotion follows: If a chicken-and-a-half can lay and egg-and-a-half in a day-and-a-half, how long would it take one regular chicken to lay a dozen eggs? Most-favorable consideration will be given to answers submitted with a valid Paypal account number and password. It need not be your own. Email answers to (There, that should about do it.) |
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Mike Coslo wrote:
How about a loss of de-Corum...... ;^) Sorry Cecil, I'm a sucker for a bad pun! I'm not sure K1AON and KB1EUD would appreciate your pun. -- 73, Cecil http://www.qsl.net/w5dxp |
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There's a good fight brewing in QEX magazine land. Eric, K8LV, wrote a
pretty good article on directional wattmeters. But he spent a lot of space asserting that the notion of forward and reflected power in a transmission line is merely for intuitive convenience, isn't real, and should be abandoned in favor of unidirectional power flow and lumped analysis at a single point. Whoo Hoo. The letters will be fun. Especially if Eric attempts to extend his assertion to a case not-as-special, such as not-steady-state or a point in 3D space. Too bad it wasn't here. Bet we'd get a couple dozen posts before the weekend's out. Anyone want to take Eric's side? 73, Glenn AC7ZN |
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Cecil Moore wrote:
Over the years, I have challenged anyone on this newsgroup to create a standing wave in a single source system without having the existence of a forward wave and a reflected wave. Nobody has furnished any proof that standing waves are possible in a single source system without the existence of forward and reflected waves. Cecil, Why would anyone try to prove that the basic math of adding sinusoidal functions is incorrect? To the contrary, you are the one who insists that a standing wave and its constituent traveling wave components are somehow different and unique. No one denies the simultaneous existence of standing waves and traveling waves. Isn't superposition wonderful! 73, Gene W4SZ |
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Gene Fuller wrote:
Why would anyone try to prove that the basic math of adding sinusoidal functions is incorrect? To the contrary, you are the one who insists that a standing wave and its constituent traveling wave components are somehow different and unique. Actually, it was you who made that assertion and thanks for the opportunity to quote you once again: Gene Fuller, W4SZ wrote: In a standing wave antenna problem, such as the one you describe, there is no remaining phase information. Any specific phase characteristics of the traveling waves died out when the startup transients died out. So standing waves are "somehow different" from traveling waves according to your own assertions. The traveling wave possesses phase characteristics and the standing wave doesn't. Phase is gone. Kaput. Vanished. Cannot be recovered. Never to be seen again. So it was you who asserted that standing wave current is "somehow different" from traveling wave current and I agree with you. It's obvious they are "somehow different" because they have different mathematical equations. Have you changed your mind since your above quoted posting? No one denies the simultaneous existence of standing waves and traveling waves. Of course they do, Gene, that is the whole point. Here is a quote from K8LV's article: "I wish to emphasize the fact that the forward and reverse waves really do not exist separately ..." That certainly *denies* the separate existence of the underlying traveling waves so your above assertion is false. I believe that W7EL also denies the separate existence of forward and reverse waves and introduced the technical term, "sloshing", to explain what happens to the energy in a transmission line with reflections. -- 73, Cecil http://www.qsl.net/w5dxp |
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Cecil wrote:
This is just one more example of the dumbing down of amateur radio accompanying the dumbing down of the US educational system in general. Unfortunately, it seems to be a trend that cannot be reversed because it is the biased view being pushed by the ARRL and its supporters. Hmmm...not sure I agree that the folks at ARRL are deliberately being dumb (or maybe I just misunderstood you). Seems more unintentional to me. After all, the technical editor of QEX let publish that bizarre article that claimed to prove by math that phasing SSB receivers were not possible. Can''t imagine a political motivation for that though I have to wonder bigtime how that one got by. QEX really really needs for some good peer review. Ah, to have Ham Radio magazine back again. Loved that thing. Learned most of my radio from it. 73, Glenn AC7ZN |
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Funny thing is that I'm down with the slow-wave loading coil thing.
Maxwell's equations are your friend... not a very nice friend when Bessel functions are involved, but... Faster than light, though? Maybe the phase velocity in some tricky cryogenic world, but I dunno... Haven't seen much on superconducting antennas here... I read a paper once with a superconducting magloop but they forgot to make the matching network superconducting too. Let's get the "bizarre but REAL" antenna thread going. Wouldn't you like to have a QRP CW rig with a 3" magloop for 20m on the top? The thermos full of liquid nitrogen is kind of a pain to lug around... Anyone built a "genetically" designed ham antenna yet? Might be a good way to go for the "I have 50 feet between two trees to put up an 80m dipole" crowd. Maybe we could develop a combined performance+aesthetics genetic algorithm to design efficient shortened vertical dipoles that look like nice pieces of modern art and have a nice low voltage section to run the coax out... you run the electromagnetic algorithm, weed out the weak designs, then you have your neighbor click the most attractive five and throw the rest out, and repeat! -Dan |
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wrote in message oups.com... Cecil wrote: This is just one more example of the dumbing down of amateur radio accompanying the dumbing down of the US educational system in general. Unfortunately, it seems to be a trend that cannot be reversed because it is the biased view being pushed by the ARRL and its supporters. Hmmm...not sure I agree that the folks at ARRL are deliberately being dumb (or maybe I just misunderstood you). Seems more unintentional to me. After all, the technical editor of QEX let publish that bizarre article that claimed to prove by math that phasing SSB receivers were not possible. Can''t imagine a political motivation for that though I have to wonder bigtime how that one got by. QEX really really needs for some good peer review. I don't think anyone is trying to be "deliberately being dumb", more like "naturally being dumb" and not knowing it. :-) Reality is that quality of technical material in ham publications is slipping, heading for stuck on stupid. Add cheapening of ham ticket exams, push for mass and no exam recruiting of new hams (a la CB wizards) in effort to boost numbers and few bad apples with it - you get the picture of deteriorating standards. When W8JI had a presentation at Dayton's Antenna Forum and spoke about his "famous - same current along the antenna loading coil", I came to K3LR (forum leader) and N6BV (ARRL Antenna Book editor) and pointed out that perhaps there is an error in W8JI assertions, I got this in private mail from the "guru": "When you pull people aside at Dayton to bitch about me or others or make wild crazy statements it just makes you look worse and worse to the people you are trying most to impress. At Dayton two years ago several people came up and told me your tried to start conversations about me with them, or that you started bitching about me." Sooo, looks like one has to take some articles in ARRL publications with biiiig grain of salt. Goofy stuff gets through, real expert material gets swept under by "know-it-alls" in charge, Goofy is right and Right is not important anymore. "Gurus" beat their drums into the publications and great confusion ensues. As far as SWR, I always tried to avoid it by matching, designing antennas to have impedance of the feedline, and the TX/Amp output matching the feedline impedance. Standing Wave Ratio always implied two waves - forward and reflected and their superposition. Why waste power in "confused" standing waves, when I can make sure that the waves are marching forward towards the antenna and be radiated. Let the waves stand in the antenna, where they belong, doing radiating and not in the lossy feedline. High SWR is not imaginary, it is real, can create excessive voltages, dielectric losses and melt the coax. Happy Mother's Day to all the mothers that did not abort us! God Bless them and thank you! Yuri, da BUm |
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wrote:
Hmmm...not sure I agree that the folks at ARRL are deliberately being dumb (or maybe I just misunderstood you). Let me just relate my personal experience. I submitted an article to QEX which mentioned light wave theory as explained in "Optics", by Hecht. An (un-named) QEX employee, with whom I was dealing, had "Optics" as a college textbook and was very interested in the subject. He suggested that I expand the light wave theory section of my article, which I did. After about four revisions, he suddenly stopped responding to my emails. A couple of months later, I received a rejection letter. That was well over a year ago. Two QEX articles have recently appeared covering exactly the same material as my article but with different slants. QEX still will not answer my emails and will not publish my letters to the editor. My treatment by QEX is more akin to religious shunning than anything else. I am convinced that the QEX employee that I was dealing with is deliberately publishing dumbed-down material because he previously indicated that he knows different from his college optics course. He is most probably being directed to do so by his superiors because he was, at first, enthusiastic about publishing my article which is available from my web page below. -- 73, Cecil http://www.qsl.net/w5dxp/energy.htm |
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Yuri Blanarovich wrote:
When W8JI had a presentation at Dayton's Antenna Forum and spoke about his "famous - same current along the antenna loading coil", ... It is unusual for W8JI to give up on an argument so abruptly. I wish I had thought of the dual-Z0 shortened stub concept years ago. -- 73, Cecil http://www.qsl.net/w5dxp |
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tell us more, 'dual-z0 shortened stub' sounds like something interesting.
"Cecil Moore" wrote in message . com... Yuri Blanarovich wrote: When W8JI had a presentation at Dayton's Antenna Forum and spoke about his "famous - same current along the antenna loading coil", ... It is unusual for W8JI to give up on an argument so abruptly. I wish I had thought of the dual-Z0 shortened stub concept years ago. -- 73, Cecil http://www.qsl.net/w5dxp |
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Dave wrote:
tell us more, 'dual-z0 shortened stub' sounds like something interesting. In my quest to explain the phase shift in a 75m bugcatcher coil, I thought about a dual-Z0 stub. The shortest 450/50 one I have come up with that causes the maximum phase shift is: ---19 deg of 450 ohm line---+---18 deg of 50 ohm line---open Believe it or not, that is an electrical 1/4WL stub with a whopping 53 degrees of *lossless* phase shift occurring at the '+' impedance discontinuity point. Are there any applications for a stub that is physically 0.1 WL long instead of 0.25WL? It could be shortened even more by using 600 ohm line with 50 ohm line. On top of everything else, the current in the 50 ohm section seems to be much lower than the current in the 600 ohm section thus reducing the losses in the stub. From these experiments, I have concluded that the phase shift in a 75m mobile loading coil may be in the ballpark of 20 degrees while the phase shift in the stinger is in the ballpark of 20 degrees with the majority of phase shift coming from the impedance discontinuity between the loading coil and the stinger. So neither side of the years-long argument was right or wrong. -- 73, Cecil http://www.qsl.net/w5dxp |
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En/na Dave ha escrit:
... Come on, just a little fight??? Just a question about coax cables: I know that a coax cable does not radiate (if common mode currents properly suppressed) because both conductors are apparently "in the same place" (wouldn't know how to express it in more technical terms). Now the question is: This is true for big distances from the coax, but is it also true when you get very close to the coax? Imagine a conductor taped to the outside of a coax for some meters. The capacitive coupling to the braid is much higher than the coupling to the inner conductor. Would it pick some of the current in the coax. If not, why not? (apart from fun I'm really interested in the answer as I'm not quite sure if a coax running parallel to unshielded and not twisted computer cables would pick harmonics from it on RX or create interferences on TX) -- Toni |
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no... and yes.... there would be some pickup, but only from leakage through
an imperfect braid. because the current is on the inside of the shield it would not couple to the cable on the outside. the electric and magnetic fields are contained completely inside the shield. "EA3FYA - Toni" wrote in message ... En/na Dave ha escrit: ... Come on, just a little fight??? Just a question about coax cables: I know that a coax cable does not radiate (if common mode currents properly suppressed) because both conductors are apparently "in the same place" (wouldn't know how to express it in more technical terms). Now the question is: This is true for big distances from the coax, but is it also true when you get very close to the coax? Imagine a conductor taped to the outside of a coax for some meters. The capacitive coupling to the braid is much higher than the coupling to the inner conductor. Would it pick some of the current in the coax. If not, why not? (apart from fun I'm really interested in the answer as I'm not quite sure if a coax running parallel to unshielded and not twisted computer cables would pick harmonics from it on RX or create interferences on TX) -- Toni |
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EA3FYA - Toni wrote:
Just a question about coax cables: I know that a coax cable does not radiate (if common mode currents properly suppressed) because both conductors are apparently "in the same place" (wouldn't know how to express it in more technical terms). Here's why it doesn't radiate: In a coaxial cable with a solid shield, the differential mode current is entirely inside the shield. Current and fields penetrate only a very small distance from the inner surface of the shield, and no significant amount ever makes it through to the outside. This is assuming that the shield is at least several skin depths thick, which is a good assumption at HF and above. Common mode current, by contrast, flows on the outside of the shield, and its field radiates outward from there. Now the question is: This is true for big distances from the coax, but is it also true when you get very close to the coax? Imagine a conductor taped to the outside of a coax for some meters. The capacitive coupling to the braid is much higher than the coupling to the inner conductor. Would it pick some of the current in the coax. If not, why not? Again assuming a solid shield -- the center conductor carries a current and therefore creates a field. The inner surface of the shield carries an equal and opposite current and also creates a field. But those fields are equal and opposite, and cancel at all points beyond a thin layer on the inner surface of the shield. Since there's no significant field at any point outside the shield, it doesn't matter where you look, you won't find any, and there isn't any field to couple to anything else. In reality, any shield other than a completely solid one (such as the shield of hard line or semi-rigid coax) will leak some because of gaps or holes. And the field will couple more strongly to wires which are close than those which are far away. Whether the amount of leakage is significant or not depends on the application. (apart from fun I'm really interested in the answer as I'm not quite sure if a coax running parallel to unshielded and not twisted computer cables would pick harmonics from it on RX or create interferences on TX) You might get enough leakage through the shield of ordinary coax to cause problems in both cases. It depends on the transmit power level, the signals in the wires, the length over which they're bundled, the frequencies involved, the quality of the shield, and so forth. Separating them even a small distance would reduce the coupling considerably. But you're likely to have more trouble with common mode current. Roy Lewallen, W7EL |
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Gene Fuller wrote:
Isn't superposition wonderful! 73, Gene W4SZ Yup, it's why I find religion so amusing. tom K0TAR |
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wrote:
Funny thing is that I'm down with the slow-wave loading coil thing. Maxwell's equations are your friend... not a very nice friend when Bessel functions are involved, but... Faster than light, though? Maybe the phase velocity in some tricky cryogenic world, but I dunno... And light has now gone faster than light. Well, sort of. It did get there before it left in this case. http://www.scienceblog.com/cms/light...rds-10590.html tom K0TAR |
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Cecil Moore wrote:
Gene Fuller wrote: Why would anyone try to prove that the basic math of adding sinusoidal functions is incorrect? To the contrary, you are the one who insists that a standing wave and its constituent traveling wave components are somehow different and unique. Actually, it was you who made that assertion and thanks for the opportunity to quote you once again: Gene Fuller, W4SZ wrote: In a standing wave antenna problem, such as the one you describe, there is no remaining phase information. Any specific phase characteristics of the traveling waves died out when the startup transients died out. So standing waves are "somehow different" from traveling waves according to your own assertions. The traveling wave possesses phase characteristics and the standing wave doesn't. Cecil, You keep making the same mistake. Yes, you can analyze traveling waves instead of standing waves if you so choose. However, there is not one bit of additional physical information in the traveling waves that is not in the standing wave. Any "phase characteristic" is simply a function of the mathematical manipulations you use. Perhaps someday you will actually understand superposition, but I won't hold my breath. 73, Gene W4SZ |
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Gene Fuller wrote:
However, there is not one bit of additional physical information in the traveling waves that is not in the standing wave. I agree with you but W8JI and W7EL have rejected the concept that there is any phase information in the standing wave current magnitude. They have rejected any use of the arc-cosine function in calculating that phase. The following graphs show the difference in the standing wave current and the traveling wave current. http://www.qsl.net/w5dxp/travstnd.GIF The standing wave current phase contains zero phase information as you have stated. As you say, all the standing wave current phase information is contained in the magnitude but the arc-cosine function for obtaining that phase information has been rejected by the experts. For the traveling wave, there is phase information contained in the phase, none in the magnitude. Every time you make a technical assertion, you support my argument. Seems your argument is really with the side that rejects the arc- cosine function for obtaining phase information. -- 73, Cecil http://www.qsl.net/w5dxp |
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En/na Roy Lewallen ha escrit:
EA3FYA - Toni wrote: I know that a coax cable does not radiate (if common mode currents properly suppressed) because both conductors are apparently "in the same place" (wouldn't know how to express it in more technical terms). Here's why it doesn't radiate: In a coaxial cable with a solid shield, the differential mode current is entirely inside the shield. Current and fields penetrate only a very small distance from the inner surface of the shield, and no significant amount ever makes it through to the outside. This is assuming that the shield is at least several skin depths thick, which is a good assumption at HF and above. When you say "Current and fields penetrate only a very small distance...", I agree for the current part, but I'm not so sure for the fields part: As I understand it you can not "stop a field" in no way, though you can certainly nullify it with an identical but opposite field. Then the question is whether the two fields (the one from the current flowing in the shield + the one from the current flowing in the inner conductor) nullify at all points in the immediate vicinity of the shield. I certainly believe it but would like to understand why this is so. I guess the mathematical proof would involve assuming the braid is an infinite number of conductors equally spaced around the center conductor, each having it's infinitesimal share of the shield current, and integrating all of their fields at the point of interest (Would probably be able to do so back when I was at university but now it is too strong math for me). Would this be a good approximation of the problem? -- Toni |
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Thanks four your answers.
I was forgetting you normally use coax in a unbalanced configuration where the braid is supposed to be at 0 voltage so only currents matter. Would all this still hold if you used the coax as a _balanced_ transmission line? (unusual but -I think- possible). In this case wouldn't voltages develop on the braid that could capacitively couple to other conductors? (assuming perfect solid shield, ...) -- Toni |
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the voltage on the braid is not zero on the inside, it varies along with the
wave traveling along the inside of the coax. and the currents are exactly balanced inside the coax also, they have to be or it wouldn't work. this notion of balanced vs un-balanced transmission lines is totally confusing to most people, in a proper system, say just with a dummy load on a coax the currents on the shield exactly balance the current on center conductor. so why do we go through all this stuff with bal-uns?? and coax chokes?? the currents are already balanced, so WHY?? come on you gurus out there, explain this one! "Toni" wrote in message ... Thanks four your answers. I was forgetting you normally use coax in a unbalanced configuration where the braid is supposed to be at 0 voltage so only currents matter. Would all this still hold if you used the coax as a _balanced_ transmission line? (unusual but -I think- possible). In this case wouldn't voltages develop on the braid that could capacitively couple to other conductors? (assuming perfect solid shield, ...) -- Toni |
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Dave wrote:
so why do we go through all this stuff with bal-uns?? and coax chokes?? the currents are already balanced, so WHY?? come on you gurus out there, explain this one! Water comes out of a hose whether the hose is leaky or not. So why ever bother patching or replacing a leaky hose? -- 73, Cecil http://www.qsl.net/w5dxp |
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Cecil Moore wrote:
Gene Fuller wrote: However, there is not one bit of additional physical information in the traveling waves that is not in the standing wave. I agree with you but W8JI and W7EL have rejected the concept that there is any phase information in the standing wave current magnitude. They have rejected any use of the arc-cosine function in calculating that phase. The following graphs show the difference in the standing wave current and the traveling wave current. http://www.qsl.net/w5dxp/travstnd.GIF The standing wave current phase contains zero phase information as you have stated. As you say, all the standing wave current phase information is contained in the magnitude but the arc-cosine function for obtaining that phase information has been rejected by the experts. For the traveling wave, there is phase information contained in the phase, none in the magnitude. Every time you make a technical assertion, you support my argument. Seems your argument is really with the side that rejects the arc- cosine function for obtaining phase information. Cecil, You still don't get it. When I said the phase information was gone, I meant it. Any phase information you think you find by looking at the constituent traveling waves is merely an artifact of the math. It has no physical meaning or reality. If there is anything interesting left in the traveling wave analysis, then the standing wave is not the complete representation of the electromagnetic phenomena. This is a different problem. Yes, you can apply modulation, insert directional couplers, look at startup transients, or perform other tricks to get "real" phase information. However, that again becomes a different problem, not the original simple steady-state combination of traveling waves into a standing wave. 73, Gene W4SZ |
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Toni wrote: En/na Roy Lewallen ha escrit: EA3FYA - Toni wrote: I know that a coax cable does not radiate (if common mode currents properly suppressed) because both conductors are apparently "in the same place" (wouldn't know how to express it in more technical terms). Here's why it doesn't radiate: In a coaxial cable with a solid shield, the differential mode current is entirely inside the shield. Current and fields penetrate only a very small distance from the inner surface of the shield, and no significant amount ever makes it through to the outside. This is assuming that the shield is at least several skin depths thick, which is a good assumption at HF and above. When you say "Current and fields penetrate only a very small distance...", I agree for the current part, but I'm not so sure for the fields part: As I understand it you can not "stop a field" in no way, though you can certainly nullify it with an identical but opposite field. You bet you can stop a field. It can be stopped either by reflection, absorption, or a combination of the two. Inside an anechoic chamber, absorbing materials stop internal fields to prevent reflections. A screen room or metallic shield reflects external fields. Then the question is whether the two fields (the one from the current flowing in the shield + the one from the current flowing in the inner conductor) nullify at all points in the immediate vicinity of the shield. I certainly believe it but would like to understand why this is so. Indeed they do. Look up Ampere's Law. If you draw a boundary through the middle of the shield or outside the shield, you'll find that the sum of currents within that boundary is zero. According to the law, that means that no net field penetrates the boundary. Because of the physical symmetry, no net field means no field at all. I guess the mathematical proof would involve assuming the braid is an infinite number of conductors equally spaced around the center conductor, each having it's infinitesimal share of the shield current, and integrating all of their fields at the point of interest (Would probably be able to do so back when I was at university but now it is too strong math for me). Would this be a good approximation of the problem? No, it's not that complicated, but a path or surface integration is required to use Ampere's law. Roy Lewallen, W7EL |
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Toni wrote:
Thanks four your answers. I was forgetting you normally use coax in a unbalanced configuration where the braid is supposed to be at 0 voltage so only currents matter. How do you define "0 voltage"? Do a groups.google.com search of this newsgroup and you'll find quite a bit of discussion about the futility of trying to define a voltage between two distant points in the presence of a field. Would all this still hold if you used the coax as a _balanced_ transmission line? (unusual but -I think- possible). In this case wouldn't voltages develop on the braid that could capacitively couple to other conductors? (assuming perfect solid shield, ...) A coax line is balanced when the common mode current is zero. It's unbalanced when common mode current exists. See http://eznec.com/Amateur/Articles/Baluns.pdf for more information. Voltages don't couple, fields do. There was also some discussion not too long ago on this group about the role of current in generating both electric and magnetic fields. Roy Lewallen, W7EL |
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Dave wrote:
the voltage on the braid is not zero on the inside, it varies along with the wave traveling along the inside of the coax. and the currents are exactly balanced inside the coax also, they have to be or it wouldn't work. this notion of balanced vs un-balanced transmission lines is totally confusing to most people, in a proper system, say just with a dummy load on a coax the currents on the shield exactly balance the current on center conductor. so why do we go through all this stuff with bal-uns?? and coax chokes?? the currents are already balanced, so WHY?? come on you gurus out there, explain this one! The currents on the inside are always balanced -- they're purely differential mode. The purpose of baluns or common mode chokes is to reduce the common mode current which, on coax, flows entirely on the outside. If you're driving a dummy load from your transmitter, the common mode current will be zero in an ideal system and negligible in a real system. A balun or common mode choke will do nothing in that situation. See http://eznec.com/Amateur/Articles/Baluns.pdf for a more complete explanation. Roy Lewallen, W7EL |
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Gene Fuller wrote:
Cecil, You still don't get it. I get what you said. Here it is again. Gene Fuller wrote: The only "phase" remaining is the cos (kz) term, which is really an amplitude description, not a phase. So you alluded to phase information in the standing wave current amplitude. When I said the phase information was gone, I meant it. But you also said: Gene Fuller wrote: However, there is not one bit of additional physical information in the traveling waves that is not in the standing wave. We know that there is phase information in the traveling waves. So for your statement to be true, there has to be phase information in the standing wave. Both of your statements cannot be true. Which one are you willing to stick with and which one are you going to retract? If you look at: http://www.qsl.net/w5dxp/travstnd.GIF you will see that the standing wave amplitude is indeed a cosine function of the phase. Taking the arc-cosine of the normalized amplitude yields the phase angle. I'm sorry, but you have contradicted yourself a couple of times so I don't know which assertion you want to go with. -- 73, Cecil http://www.qsl.net/w5dxp |
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Gene Fuller wrote:
Cecil Moore wrote: Gene Fuller wrote: However, there is not one bit of additional physical information in the traveling waves that is not in the standing wave. I agree with you but W8JI and W7EL have rejected the concept that there is any phase information in the standing wave current magnitude. They have rejected any use of the arc-cosine function in calculating that phase. The following graphs show the difference in the standing wave current and the traveling wave current. . . . Egad. Of course I reject the notion that there's "phase information in the standing wave current magnitude". Magnitude and phase are orthogonal. There's no phase in the magnitude and no magnitude in the phase. There's no real portion of the imaginary part and no imaginary portion of the real part. I haven't a clue what you mean by "use of the arc-cosine,function to calculate that phase", but I certainly reject any method that assigns a phase value to a magnitude or vice versa. I get the total voltage or current simply by adding the traveling waves. No trig functions necessary, just simple vector addition. Traveling waves have phase information. In a steady state system they can be expressed as phasors, which consist of a magnitude, a time phase reference value, and an implicit time varying time rotation. When you add them to get the total (which Cecil likes to characterize as a standing wave as though it's something different than just the total voltage or current), you get the simple vector sum of the constituent traveling waves. This sum is also a phasor, with magnitude, time phase reference value, and the same implicit time varying phase rotation. In summary, both traveling waves and the total voltage or current are phasors, and both have phase. What's so complicated about adding a couple of phasors? Cecil, you need to go back and read, and understand, your freshman circuit analysis text. What a bunch of irrational smoke and mirrors. I don't care less what Cecil will make of this. But Gene, do you really disagree with what I've just said? Roy Lewallen, W7EL |
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Roy Lewallen wrote:
Egad. Of course I reject the notion that there's "phase information in the standing wave current magnitude". And, of course, you are showing your ignorance. Let's say that at the current maximum point, the forward current is 0.5 at 0 deg and the reflected current is 0.5 at 0 deg. The standing wave current at the current maximum point is 1.0 at 0 deg just like a cosine function is 1.0 at 0 deg. Now let's go 45 degrees away from that current maximum point. The forward current is 0.5 at -45 deg and the reflected current is 0.5 at +45 deg so the standing wave current is 0.707 at 0 deg. The magnitude of the standing wave current is 0.707. The arc- cosine of 0.707 is 45 degrees. Do you really and truly believe that is just a coincidence? Exactly as Gene Fuller said previously, there is phase information in the standing wave current magnitude. Here's a quote from Gene: Gene Fuller wrote: The only "phase" remaining is the cos (kz) term, which is really an amplitude description, not a phase. Your statement above is in direct contradiction to Gene's statement. What's so complicated about adding a couple of phasors? I suspect you know how to add phasors. I suspect you don't have a clue what that answer means in reality. Please try to convince us that the 0.707 result above for a 45 degree shift is sheer coincidence. -- 73, Cecil http://www.qsl.net/w5dxp |
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Roy Lewallen wrote:
I don't care less what Cecil will make of this. But Gene, do you really disagree with what I've just said? Roy Lewallen, W7EL Roy, I do not disagree with anything you have said. Cecil is up to his standard trick of selective quoting along with a subtle change of topic to make it appear that there are conflicts when there are none. I am sure Cecil will find some other quote to remove from context in order to prove me wrong. 73, Gene W4SZ |
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Cecil Moore wrote:
Gene Fuller wrote: Cecil, You still don't get it. I get what you said. Here it is again. Gene Fuller wrote: The only "phase" remaining is the cos (kz) term, which is really an amplitude description, not a phase. So you alluded to phase information in the standing wave current amplitude. When I said the phase information was gone, I meant it. But you also said: Gene Fuller wrote: However, there is not one bit of additional physical information in the traveling waves that is not in the standing wave. We know that there is phase information in the traveling waves. So for your statement to be true, there has to be phase information in the standing wave. Both of your statements cannot be true. Which one are you willing to stick with and which one are you going to retract? If you look at: http://www.qsl.net/w5dxp/travstnd.GIF you will see that the standing wave amplitude is indeed a cosine function of the phase. Taking the arc-cosine of the normalized amplitude yields the phase angle. I'm sorry, but you have contradicted yourself a couple of times so I don't know which assertion you want to go with. Cecil, I have not contradicted myself, and I have nothing to retract. Only in your imagination is there any useful phase information in the traveling waves that make up a standing wave. There can be other waves that don't exactly balance out into a standing wave, but that is another topic. I am not sure to whom the "we" refers in your statement, "We know that there is phase information in the traveling waves." Perhaps that is the Royal We, because it certainly does not include me. The phase information you might find is of no use, and it is simply an artifact of the mathematical analysis. If the standing wave adequately and completely describes the electromagnetic situation, then there is no additional available from an arbitrary decomposition in traveling waves. If you try to look at the traveling waves one at a time, then you are no longer considering a standing wave. 73, Gene W4SZ |
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"Gene Fuller" wrote in message ... Cecil Moore wrote: Gene Fuller wrote: Cecil, You still don't get it. I get what you said. Here it is again. So you alluded I meant it. But you also said: there is not one bit of additional physical information So for your statement to be true, there has to be Both of your statements cannot be true. Which one are you willing to stick with and which one are you going to retract? If you look at I'm sorry, but you have contradicted yourself a couple of times so I don't know which assertion you want to go with. I have not contradicted myself, and I have nothing to retract. but that is another topic. I am not sure to whom the "we" refers in your statement, Perhaps that is the Royal We, because it certainly does not include me. there is no additional available from COME ON! KEEP IT GOING!! this rainy wet weekend is almost over and I could use one more good round of laughter!! Perhaps we cut straight to the conclusion and have something that is completely a personal attack devoid of any possible technical statements, that would do nicely! DON'T STOP NOW! |
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Gene Fuller wrote:
I do not disagree with anything you have said. Please answer this question. Does the amplitude of the standing wave current contain any phase information? You have previously asserted that it does. Roy says it doesn't. Time to chose between technical fact and agreeing with your friend (who is technically incorrect). -- 73, Cecil http://www.qsl.net/w5dxp |
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Gene Fuller wrote:
I have not contradicted myself, ... Either the standing wave current magnitude contains phase information, as you previously asserted, or it doesn't. I'll make it easy for you. Just insert an 'X' for the one you agree with. _____ Standing wave current magnitude contains some phase information. _____ Standing wave current magnitude contains zero phase information. -- 73, Cecil http://www.qsl.net/w5dxp |
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