|
Jim Kelley wrote:
Cecil Moore wrote: Following your logic, two people shooting at each other with identical bullets can do no harm because the net energy is zero. Care to prove your theory? How many sources ya got in that example, Cecil? Is that the same to you? If it is, then I can see why you don't understand. Couldn't possibly be that you don't understant, huh? Someone has shot a bullet into an iron wash pot. It ran around the rim of the pot and changed directions by 180 degrees. Just as it was changing directions, another bullet was fired from the same gun. The returning bullet has less energy than the second bullet. Therefore, the net energy is away from the gun. Want to stick your head in front of the ricochet bullet to prove that component energy doesn't matter? -- 73, Cecil http://www.qsl.net/w5dxp |
I'm probably not the only one that is getting an adequate fill of facts,
opinions and quotes. I have only one request. Does anyone have verifiable and repeatable evidence that a properly tuned pi network final amplifier without a tuner does or does not dissipate power when there are reflections? If they do can they please direct us to the source or give us an easliy understandable write up. tnx -- 73 Hank WD5JFR "alhearn" wrote in message om... "Steve Nosko" wrote in message ... OH! NO! Vortex vs. Bernoulli Actually, it's Circulation vs. Newtonian vs. Bernoulli -- all three are different mathmatical means of describing accurately and precisely what happens when a airfoil produces lift. Actually each is simply a different way of expressing exactly the same thing, but none of them translates well to a real-life understanding of the concept. One of the problems is that causes and effects get confused and oversimplified by the math. Much the same with reflections, transmission lines, and impedance matching. While reflections do indeed exist on transmission lines when mismatched to a source or load, they simply create standing waves. Standing waves create non-optimum impedances depending on the characteristics and length of the line. These impedances interact with source and load impedances in very predictable and calculated ways. Efficiency of power transfer is then determined by optimizing the matching of these impedances. Optimimizing impedances then eliminates reflections --- a circle of causes and effects. Mathmatically, it's more expedient to skip much of the in-between cause-and-effect stuff, and jump directly to describing the entire process as a direct relationship between reflections and power transfer -- which causes problems when attempting to visualize or explain the process -- because that's not the way it really works. It's not quite that simple and direct. A standard SWR meter is a good example. It can't conveniently measure reflections OR standing waves, so it measures mismatch. Since everything is directly related, it could be said that it measures reflections -- but it really doesn't. So, it doesn't really matter unless you try to understand how the meter works in terms of how it measures reflections or standing waves. Al |
WARNING! I use the sinusoidal steady state assumptions for this
explanation, this means that all reflection transients have died out and the input signal is not changing. These are generally good assumptions for general use that does not depend on signal changing on a time scale similar to the reflection period, like radar or fast scan tv.... for cw, am, and even ssb in amateur sized systems these are generally very good and yeild answers that are more than adequate to answer problems like this. given the above its very simple. look at the coax connector as if it was a connector on a black box, there are no reflections. period. the input of the black box looks like a simple linear impedance. the procedure to find out how it affects your pi network is this: use your favorite circuit modeling program and model the linear and output network to whatever degree of detail you see fit. attach a load of 50+j0 and determine currents and voltages in the matching network. (note that you will have to include real world losses in the inductors and capacitors if you want to calculate power dissipation in them). change load to however bad a condition you want to model and compare currents and voltages to the 50 ohm case. this will show you if more or less power is lost in the matching network. if you have modeled a tube or fet with real world parameters it will also tell you if it's dissipation goes up or down. "Henry Kolesnik" wrote in message . .. I'm probably not the only one that is getting an adequate fill of facts, opinions and quotes. I have only one request. Does anyone have verifiable and repeatable evidence that a properly tuned pi network final amplifier without a tuner does or does not dissipate power when there are reflections? If they do can they please direct us to the source or give us an easliy understandable write up. tnx -- 73 Hank WD5JFR "alhearn" wrote in message om... "Steve Nosko" wrote in message ... OH! NO! Vortex vs. Bernoulli Actually, it's Circulation vs. Newtonian vs. Bernoulli -- all three are different mathmatical means of describing accurately and precisely what happens when a airfoil produces lift. Actually each is simply a different way of expressing exactly the same thing, but none of them translates well to a real-life understanding of the concept. One of the problems is that causes and effects get confused and oversimplified by the math. Much the same with reflections, transmission lines, and impedance matching. While reflections do indeed exist on transmission lines when mismatched to a source or load, they simply create standing waves. Standing waves create non-optimum impedances depending on the characteristics and length of the line. These impedances interact with source and load impedances in very predictable and calculated ways. Efficiency of power transfer is then determined by optimizing the matching of these impedances. Optimimizing impedances then eliminates reflections --- a circle of causes and effects. Mathmatically, it's more expedient to skip much of the in-between cause-and-effect stuff, and jump directly to describing the entire process as a direct relationship between reflections and power transfer -- which causes problems when attempting to visualize or explain the process -- because that's not the way it really works. It's not quite that simple and direct. A standard SWR meter is a good example. It can't conveniently measure reflections OR standing waves, so it measures mismatch. Since everything is directly related, it could be said that it measures reflections -- but it really doesn't. So, it doesn't really matter unless you try to understand how the meter works in terms of how it measures reflections or standing waves. Al |
Gene Fuller wrote:
Note that he uses "imagine", not required, essential, or any other mandatory word. You know that I know, "imagine" is just an expression authors use in the remote event that there might ever be a standing wave without a forward and reverse wave. All I am asking is for you to provide just one example where standing waves are not caused by forward and reverse waves. You guys mealymouth all around that challenge but NEVER have provided a decent answer. If you are not going to provide that requested example, IMO, you have nothing to say worth listening to. So Gene, please, put up or shut up, and please stop jerking us off. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Henry Kolesnik wrote:
I'm probably not the only one that is getting an adequate fill of facts, opinions and quotes. I have only one request. Does anyone have verifiable and repeatable evidence that a properly tuned pi network final amplifier without a tuner does or does not dissipate power when there are reflections? If they do can they please direct us to the source or give us an easliy understandable write up. Hank, when reflected current flows backwards through a pi-net loading coil, some of the reflected power is dissipated as I^2*R losses in the coil. Other than that, a properly tuned pi-net causes a match point that reflects all the reflected energy back toward the load. If a match point exists in a ham radio antenna system, no reflected energy will reach the source. This is the great majority of amateur radio systems and no-reflections-at-the-source is the goal of every ham. The thing that you are worried about is the unusual case where reflections are allowed to reach the source. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Dave wrote:
... for cw, am, and even ssb in amateur sized systems these are generally very good and yeild answers that are more than adequate to answer problems like this. Yep, pretty good for answering the transmitter question. Not so good for answering the question of what happens between a tuner and an antenna. One must remember that with your method, one is dealing with virtual impedances, i.e. voltage to current ratios, which are themselves a result and not the cause of anything. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Cecil,
Wow! Struck a nerve. Must be close to the truth. I have said repeatedly that the alternative technical descriptions co-exist. I have never said that one "causes" the other. That would be folly, since we are dealing with math models, not physical cause and effect. Let me turn the arrow back to you. Give us one example where forward and reverse waves "cause" a standing wave, and then prove that it's not the other way 'round. I am not aware of any credible technical writing on the subject of cause and effect in these matters, so I am anxiously awaiting your answer. (Hint: Don't waste your time.) And as to "shut up", yes, I will now do that. Until next time . . 73, Gene W4SZ Cecil Moore wrote: Gene Fuller wrote: Note that he uses "imagine", not required, essential, or any other mandatory word. You know that I know, "imagine" is just an expression authors use in the remote event that there might ever be a standing wave without a forward and reverse wave. All I am asking is for you to provide just one example where standing waves are not caused by forward and reverse waves. You guys mealymouth all around that challenge but NEVER have provided a decent answer. If you are not going to provide that requested example, IMO, you have nothing to say worth listening to. So Gene, please, put up or shut up, and please stop jerking us off. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Cecil Moore wrote: Jim Kelley wrote: Cecil Moore wrote: Following your logic, two people shooting at each other with identical bullets can do no harm because the net energy is zero. Care to prove your theory? How many sources ya got in that example, Cecil? Is that the same to you? If it is, then I can see why you don't understand. Couldn't possibly be that you don't understant, huh? Bullets and radio waves? No. Matter behaves differently than do electromagnetic waves. I'm quite confident about that. 73, Jim AC6XG |
Gene Fuller wrote:
Give us one example where forward and reverse waves "cause" a standing wave, and then prove that it's not the other way 'round. Too easy, Gene. Do a web search. *ALL* demonstrations of standing waves on the web using javascript have the standing wave *caused* by superposition of a forward wave and a reverse wave. There are hundreds, if not thousands, of examples. If standing waves could exist without forward and reflected waves, don't you think someone of your own steady-state cult would have provided an example by now? Again, I challenge you (or anyone else) to provide an example of standing waves in a transmission line without forward-traveling and rearward- traveling waves. Is just one example, one tiny example, of what you are asserting, too much to ask? Apparently it is. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Reg, enjoyed reading your reply, thanks.
73 Gary N4AST |
Jim Kelley wrote:
Bullets and radio waves? No. Matter behaves differently than do electromagnetic waves. I'm quite confident about that. So what? Some matter behaves differently from other matter. Hint: Jim, here's a heads-up for you. You must be omnipotent in order to prove that you are omniscient. I hope you are up to that task. My challenge still stands. Please provide a standing wave without a forward-traveling wave and a rearward-traveling wave. If you can't, at least send me a joint of whatever you are smokin'. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
"Henry Kolesnik" wrote in message ...
I'm probably not the only one that is getting an adequate fill of facts, opinions and quotes. I have only one request. Does anyone have verifiable and repeatable evidence that a properly tuned pi network final amplifier without a tuner does or does not dissipate power when there are reflections? If they do can they please direct us to the source or give us an easliy understandable write up. If you read Chapter 13, "RF Power Amplifiers and Projects", in the 2004 ARRL Handbook, there are pages and pages of discussion of matching plate or transistor output impedances to 50 ohms output and not once do they ever refer to output networks dissipating or reflecting reflected power. Not once. It's always a matter of simply matching one impedance to another to provide the highest power output consistent with required linearity, while staying within the amplifiying device's ratings. Transmission lines have reflections; output matching networks and tuners don't. The reflections on transmission lines don't make it past the end of the transmission line -- that's where the reflections take place. Beyond the end of the transmission line, the reflections are seen as mere impedances created by standing waves, which are created by reflections, assuming mismatch. Al |
|
Richard said -
True, but only insofar as the tuner is adjusted to offer a conjugate. ================================ Richard, how many more times do I have to tell you? The impedance looking back into the tuner is NOT the conjugate of the impedance looking into the transmission line towards the antenna - not even when the tuner is adjusted for SWR = 1-to-1. You lead people astray. Or did you make the assertion just to irritate yours truly? ---- Reg, G4FGQ |
On Fri, 28 May 2004 05:37:07 +0000 (UTC), "Reg Edwards"
wrote: Richard said - True, but only insofar as the tuner is adjusted to offer a conjugate. ================================ Richard, how many more times do I have to tell you? One wonders how many more times indeed, must be love. You lead people astray. Jealous? Or did you make the assertion just to irritate yours truly? oooooo! 88's Richard Clark, KB7QHC Seriously, ducky, do you have any numbers, or is this the Brit version of foreplay? |
alhearn wrote:
If you read Chapter 13, "RF Power Amplifiers and Projects", in the 2004 ARRL Handbook, there are pages and pages of discussion of matching plate or transistor output impedances to 50 ohms output and not once do they ever refer to output networks dissipating or reflecting reflected power. Not once. It's always a matter of simply matching one impedance to another Sorry, that isn't correct. Maybe the Handbook doesn't emphasize the point clearly enough, but the design of output networks is specifically *not* about impedance "matching". The objective is to *transform* the impedance of the load at the amplifier's output socket (usually the design value of 50R) into the correct value of load impedance needed by the amplifier device. As Al says, the correct value of load impedance for the amplifying device is the one that will: provide the highest power output consistent with required linearity, while staying within the amplifiying device's ratings. The whole point is to understand that the output network is not trying to match any particular impedance. It's simply giving the amplifying device the load impedance it needs in order to function correctly. Those two objectives are not the same... and understanding the difference is vital for this whole discussion. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Henry Kolesnik wrote:
I'm probably not the only one that is getting an adequate fill of facts, opinions and quotes. I have only one request. Does anyone have verifiable and repeatable evidence that a properly tuned pi network final amplifier without a tuner does or does not dissipate power when there are reflections? If they do can they please direct us to the source or give us an easliy understandable write up. Sorry, Hank, I don't believe you can hope for that. In all innocence, you have rigged the question so that it only allows certain kinds of answers. It has to be a pi network. It has to be "properly" tuned. There have to be reflections. The question is tied up so tight by its built-in assumptions - the things you believe you already know - that there may not even *be* a correct answer. Time after time, this same discussion about "reflected power" fails to reach any agreed answer. Time after time, we run the same maze like lab rats... only more predictably... and every time, we fail to reach the goal of a clear, agreed understanding. And the conclusion of these experiments? That the concept of "reflected power" is not helping us to understand anything. The irony is that nobody actually *needs* that concept, so you don't ever *need* to enter that maze. Everything about standing waves on transmission lines can be understood much more clearly by thinking only about forward and reflected voltage/current waves. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
alhearn wrote:
If you read Chapter 13, "RF Power Amplifiers and Projects", in the 2004 ARRL Handbook, there are pages and pages of discussion of matching plate or transistor output impedances to 50 ohms output and not once do they ever refer to output networks dissipating or reflecting reflected power. However, the 15th edition of the ARRL Antenna Book goes into great detail about how a match point reflects rearward-traveling waves. If you are designing RF Power Amps, you can simulate load conditions with lumped components. If you are trying to figure out what happens on a transmission line (distributed network) you need to take reflections into account. Transmission lines have reflections; output matching networks and tuners don't. The reflections on transmission lines don't make it past the end of the transmission line -- that's where the reflections take place. Beyond the end of the transmission line, the reflections are seen as mere impedances created by standing waves, which are created by reflections, assuming mismatch. Impedances created by standing waves are merely V/I ratios, i.e. virtual impedances. They are the result of standing waves and not the cause of anything. Physical impedance discontinuities are the cause of reflections that cause standing waves. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
"Ian White, G3SEK" wrote And the conclusion of these experiments? That the concept of "reflected power" is not helping us to understand anything. ============================ I've been saying for years, the so-called SWR-meter is itself the root of the trouble - it has forward and reflected power scales on it. So it is impossible to refer to it without becoming emotionally involved with the highly misleading reflected power notion. Furthermore, the confounded thing doesn't even measure SWR. How can it measure SWR on a transmission line which does not exist? It is a ridiculous, meaningless situation. People drag themseves off to UHF to air their knowledge about such things as echos, S-parameters, circulators and high power TV transmitters. Quite irrelevant to the notion of reflected power at 1.8 MHz. All that's necessary is to erase the meter scales, or at least wash them from our minds, and change the name of the SWR meter to the TLI. (Transmitter Loading Indicator). Or some other more appropriate name. ---- Reg, G4FGQ |
Reg Edwards wrote:
Richard said - True, but only insofar as the tuner is adjusted to offer a conjugate. Richard, how many more times do I have to tell you? The impedance looking back into the tuner is NOT the conjugate of the impedance looking into the transmission line towards the antenna - not even when the tuner is adjusted for SWR = 1-to-1. Would you guys please define "conjugate". The following system is matched. Is there a conjugate in there somewhere? To the right of the match point? XMTR---50 ohm feedline---x---1/4WL 75 ohm feedline---112.5 ohm load -- TNX & 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Reg Edwards wrote:
All that's necessary is to erase the meter scales, or at least wash them from our minds, and change the name of the SWR meter to the TLI. (Transmitter Loading Indicator). Or some other more appropriate name. Reg, what would you call the SWR meter calibrated for 300 ohms that I have installed in the 300 ohm line to my 20m-10m dipole? -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Reg, what would you call the SWR meter calibrated for 300 ohms
that I have installed in the 300 ohm line to my 20m-10m dipole? -- 73, Cecil ============================ It depends on which end of the line you have installed it. Or are you hedging your bets by locating it at the half-way point? But wherever it is, it does not measure SWR. Just because you may think it does, does not make it so! But it's good to see you didn't disagree with me about TLI's ---- Reg |
"Reg Edwards" wrote in message ... "Ian White, G3SEK" wrote And the conclusion of these experiments? That the concept of "reflected power" is not helping us to understand anything. ============================ I've been saying for years, the so-called SWR-meter is itself the root of the trouble - it has forward and reflected power scales on it. So it is impossible to refer to it without becoming emotionally involved with the highly misleading reflected power notion. Furthermore, the confounded thing doesn't even measure SWR. How can it measure SWR on a transmission line which does not exist? It is a ridiculous, meaningless situation. People drag themseves off to UHF to air their knowledge about such things as echos, S-parameters, circulators and high power TV transmitters. Quite irrelevant to the notion of reflected power at 1.8 MHz. All that's necessary is to erase the meter scales, or at least wash them from our minds, and change the name of the SWR meter to the TLI. (Transmitter Loading Indicator). Or some other more appropriate name. ---- Reg, G4FGQ Reg Just so I can get my thinking straight -- Does a slotted line measure VSWR? Jerry |
Cecil Moore wrote: You must be omnipotent in order to prove that you are omniscient. I hope you are up to that task. I'll try and remember that. 8-| My challenge still stands. Please provide a standing wave without a forward-traveling wave and a rearward-traveling wave. If you can't, at least send me a joint of whatever you are smokin'. Wow. Maybe I need to issue a "challenge". How about this: If you can't prove that F does not equal m*a, then I am right about whatever issue on which we disagree! Is that how it works, Cecil? ;-) 73, Jim AC6XG |
Just so I can get my thinking straight -- Does a slotted line measure
VSWR? ============================ No! A slotted line cannot measure VSWR. But the VSWR on a slotted line can be measured. That is what it is there for. The slot allows access by a probe to the inner conductor. It does not allow or facillitate the measurement of VSWR on any line other than on itself. It is primarily used to make impedance measurements of R+jX etc in a standards laboratory. The Ohmic Standard is the characteristic impedance, Zo, of its own internal transmission line. Very accurate and stable. ---- |
Reg Edwards wrote:
But it's good to see you didn't disagree with me about TLI's The 'brains' over on sci.physics.electromag tell me that it takes only a couple of feet of 50 ohm coax on each side of an "SWR meter" to guarantee that it exists in a 50 ohm environment. I indeed do have three feet of RG-400 on each side of mine. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Jim Kelley wrote:
How about this: If you can't prove that F does not equal m*a, then I am right about whatever issue on which we disagree! Is that how it works, Cecil? ;-) That's how your logic obviously works, Jim. Most of us know that it is impossible to prove a negative except for a binary outcome. Please, pretty please with cream and sugar on it, provide just one single example of a standing wave without forward-traveling or rearward-traveling components. That is certainly not too much to ask. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Reg Edwards wrote:
"Ian White, G3SEK" wrote And the conclusion of these experiments? That the concept of "reflected power" is not helping us to understand anything. ============================ I've been saying for years, the so-called SWR-meter is itself the root of the trouble - it has forward and reflected power scales on it. So it is impossible to refer to it without becoming emotionally involved with the highly misleading reflected power notion. Furthermore, the confounded thing doesn't even measure SWR. How can it measure SWR on a transmission line which does not exist? It is a ridiculous, meaningless situation. People drag themseves off to UHF to air their knowledge about such things as echos, S-parameters, circulators and high power TV transmitters. Quite irrelevant to the notion of reflected power at 1.8 MHz. All that's necessary is to erase the meter scales, or at least wash them from our minds, and change the name of the SWR meter to the TLI. (Transmitter Loading Indicator). Or some other more appropriate name. Technically correct, but far too late. "SWR" is everywhere - the genie is out of the bottle, and it won't go back. To expand on what Reg already knows, but clear needs to be said again and again... The only way forward is for everybody to understand that SWR numbers are just one of several alternatives for judging the "goodness" of an impedance match to some specified reference impedance. Other alternatives include reflection coefficient, return loss, gamma, S11, etc. All these alternatives are equally valid, and any one can easily be converted to any other by doing a small amount of math. RF engineers do it all the time, and it's absolutely no big deal. If you're only using "SWR" as a number that indicates the goodness of an impedance match, you can legitimately apply it to *anything* that possesses an impedance (it doesn't need to have waves standing on it). The discussion goes off the rails when someone starts to imagine that an "SWR meter" is truly *measuring* standing wave ratio. It isn't - it is actually measuring one of those other quantities (magnitude of reflection coefficient). Then there has to be a mathematical conversion from that number into the more familiar SWR number, which is done by calibrating the meter scale in a specific non-linear way. It's vital to understand that difference: the instrument is *calibrated* in SWR, but it is actually *measuring* something else. Likewise it's a mistake to believe that a Bird Thruline wattmeter is measuring "forward and reflected watts". It is just another gadget for measuring reflection coefficient, with a fixed sensitivity that allows the meter scale to be calibrated in watts. But it's only a calibration in terms of power - the Bird is not making a power measurement. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
The ONLY thing an SWR meter measures is the "Magnitude of the reflection
coefficient relative to an arbitrary value of Ro", where Ro is usually 50 ohms. It actually throws away the other half of the possible information, ie., the "Reflection Coefficient Angle". 99.9 percent of radio amateurs have never heard of such a quantity. There's no reason why they should. It's of no practical use or interest. But they are VERY interested in whether or not their transmitter is correctly loaded with 50+j0 ohms during transmissions and a simple indicating instrument is essential. Isn't it time some enterprising manufacturer came into the market? --- Reg, G4FGQ "Ian White, G3SEK" wrote in message ... Reg Edwards wrote: "Ian White, G3SEK" wrote And the conclusion of these experiments? That the concept of "reflected power" is not helping us to understand anything. ============================ I've been saying for years, the so-called SWR-meter is itself the root of the trouble - it has forward and reflected power scales on it. So it is impossible to refer to it without becoming emotionally involved with the highly misleading reflected power notion. Furthermore, the confounded thing doesn't even measure SWR. How can it measure SWR on a transmission line which does not exist? It is a ridiculous, meaningless situation. People drag themseves off to UHF to air their knowledge about such things as echos, S-parameters, circulators and high power TV transmitters. Quite irrelevant to the notion of reflected power at 1.8 MHz. All that's necessary is to erase the meter scales, or at least wash them from our minds, and change the name of the SWR meter to the TLI. (Transmitter Loading Indicator). Or some other more appropriate name. Technically correct, but far too late. "SWR" is everywhere - the genie is out of the bottle, and it won't go back. To expand on what Reg already knows, but clear needs to be said again and again... The only way forward is for everybody to understand that SWR numbers are just one of several alternatives for judging the "goodness" of an impedance match to some specified reference impedance. Other alternatives include reflection coefficient, return loss, gamma, S11, etc. All these alternatives are equally valid, and any one can easily be converted to any other by doing a small amount of math. RF engineers do it all the time, and it's absolutely no big deal. If you're only using "SWR" as a number that indicates the goodness of an impedance match, you can legitimately apply it to *anything* that possesses an impedance (it doesn't need to have waves standing on it). The discussion goes off the rails when someone starts to imagine that an "SWR meter" is truly *measuring* standing wave ratio. It isn't - it is actually measuring one of those other quantities (magnitude of reflection coefficient). Then there has to be a mathematical conversion from that number into the more familiar SWR number, which is done by calibrating the meter scale in a specific non-linear way. It's vital to understand that difference: the instrument is *calibrated* in SWR, but it is actually *measuring* something else. Likewise it's a mistake to believe that a Bird Thruline wattmeter is measuring "forward and reflected watts". It is just another gadget for measuring reflection coefficient, with a fixed sensitivity that allows the meter scale to be calibrated in watts. But it's only a calibration in terms of power - the Bird is not making a power measurement. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
But they are VERY interested in whether or not their transmitter is
correctly loaded with 50+j0 ohms during transmissions and a simple indicating instrument is essential. Isn't it time some enterprising manufacturer came into the market? --- Reg, G4FGQ The first such instrument will probably have "Made in China" on its back. |
Cecil Moore wrote: Jim Kelley wrote: How about this: If you can't prove that F does not equal m*a, then I am right about whatever issue on which we disagree! Is that how it works, Cecil? ;-) That's how your logic obviously works, Jim. Most of us know that it is impossible to prove a negative except for a binary outcome. Please, pretty please with cream and sugar on it, provide just one single example of a standing wave without forward-traveling or rearward-traveling components. That is certainly not too much to ask. It's certainly no more than I was asking you to do. 73, Jim AC6XG |
Jim Kelley wrote:
Cecil Moore wrote: Please, pretty please with cream and sugar on it, provide just one single example of a standing wave without forward-traveling or rearward-traveling components. That is certainly not too much to ask. It's certainly no more than I was asking you to do. On the contrary, you asked me to prove a negative, a logical impossibility, e.g., prove that you have never robbed a bank. Not getting caught is NOT proof. OTOH, all I am asking from you is one measly example out of the multitudes of your postings in which examples have been alluded. If I paid you $100, would you please produce such an example? -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Cecil Moore wrote: OTOH, all I am asking from you is one measly example out of the multitudes of your postings in which examples have been alluded. If I paid you $100, would you please produce such an example? You know, you could save yourself and everyone else a lot of grief if you would actually try to find even a single example of where I ever said forward and reverse waves don't produce a standing wave. Why would I say that, Cecil? Why do YOU make this claim? Why do you insist on putting words in my mouth? It's the one thing you and I have always agreed on - that, and interference in general. For cryin' out loud, man. We've got some issues for sure, but that ain't one of 'em. 73, Jim AC6XG |
On Wed, 02 Jun 2004 11:41:57 -0700, Jim Kelley
wrote: If I paid you $100, would you please produce such an example? Asking to prove a negative? We've got some issues for sure, but that ain't one of 'em. Trying to prove a negative? |
Richard Clark wrote:
On Wed, 02 Jun 2004 11:41:57 -0700, Jim Kelley wrote: If I paid you $100, would you please produce such an example? Asking to prove a negative? We've got some issues for sure, but that ain't one of 'em. Trying to prove a negative? Prove the impossible. The deal is to replace someone's remarks with a ludicrous claim that you invent. Then challenge that person to prove the invented claim. It's impossible, so in a completely fabricated, fictitious and trivial sort of way, you win! It's as if a need to win had taken precedence over integrity. 73, ac6xg |
Jim wrote,
Richard Clark wrote: On Wed, 02 Jun 2004 11:41:57 -0700, Jim Kelley wrote: If I paid you $100, would you please produce such an example? Asking to prove a negative? We've got some issues for sure, but that ain't one of 'em. Trying to prove a negative? Prove the impossible. The deal is to replace someone's remarks with a ludicrous claim that you invent. Then challenge that person to prove the invented claim. It's impossible, so in a completely fabricated, fictitious and trivial sort of way, you win! It's as if a need to win had taken precedence over integrity. 73, ac6xg Yep, that's one of Cecil's techniques, all right. It isn't used solely to win, though. It's more a means of making your opponent look ridiculous to those who haven't been following the arguments. It's a dumb stunt that usually backfires, but, hey!, that's Cecil. 73, Tom Donaly, KA6RUH |
Jim Kelley wrote:
You know, you could save yourself and everyone else a lot of grief if you would actually try to find even a single example of where I ever said forward and reverse waves don't produce a standing wave. Where did I go wrong in the following logic? You have said there is no energy in those reverse-traveling waves. Waves cannot exist without energy. Therefore, reflected waves don't exist. Since they don't exist, they cannot cause standing waves. -- 73, Cecil http://www.qsl.net/w5dxp |
Tdonaly wrote:
Yep, that's one of Cecil's techniques, all right. It isn't used solely to win, though. It is often the result of me confusing the postings of two people with similar names. It is also often the result of logical deduction. For instance: Someone says, "Reflected waves contain no energy moving past a point." Since waves cannot exist without energy moving past a point, we can deduce that the person has strongly implied that reflected waves don't exist. -- 73, Cecil http://www.qsl.net/w5dxp |
Cecil Moore wrote:
Where did I go wrong in the following logic? You have said there is no energy in those reverse-traveling waves. Waves cannot exist without energy. Therefore, reflected waves don't exist. Since they don't exist, they cannot cause standing waves. You went wrong in the first sentence. That statement is false. The second sentence is an over-simplification, and is logically dependent upon the first sentence being true. As a result the third sentence also has a faulty premise. 73, Jim AC6XG |
Cecil Moore wrote:
Since waves cannot exist without energy moving past a point, we can deduce that the person has strongly implied that reflected waves don't exist. 100 watt rf generator driving an open, lossless transmission line. How much energy do you think moves past a given point along the line every second? 100 Joules, 200 Joules, or zero Joules? 73, Jim AC6XG |
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