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Facts
Fact 1.
Any loading coil of finite length contributes towards to the total radiation. Fact 2. The input and output currents of a loading coil of finite length are always different from each other. Fact 3. The radiation pattern of a short vertical is fixed and remains independent of the location/height of the loading coil. Fact 4. Computer programs do not tell gospel truths. They are at least as unreliable as their human programmers. ---- Reg. |
As posted in a previous thread go to www.carolyns-creations.com/ve6cb to
view the (modeled) current distribution on an 84" monopole at 21.3 MHz. Frank "Reg Edwards" wrote in message ... Fact 1. Any loading coil of finite length contributes towards to the total radiation. Fact 2. The input and output currents of a loading coil of finite length are always different from each other. Fact 3. The radiation pattern of a short vertical is fixed and remains independent of the location/height of the loading coil. Fact 4. Computer programs do not tell gospel truths. They are at least as unreliable as their human programmers. ---- Reg. |
Reg Edwards wrote:
The input and output currents of a loading coil of finite length are always different from each other. There's hardly any "input and output currents" for a loading coil in a standing wave antenna. That concept is why W8JI is in trouble with his explanations. What is actually being measured is the magnitude of the standing current wave. There is forward current flowing into the bottom of the coil and out the top. There is reflected current flowing into the top of the coil and out the bottom. The net current is a standing current wave. If we, as Kraus suggests, assume that the forward current equals the reflected current (relatively small error in doing so) then there is zero net current flowing in and out of the coil. The standing wave current is, well, just standing there and is not "going" anywhere. The gross error that a lot of people are making is that standing wave current flows. If the forward and reflected currents are equal, as Kraus assumes for purpose of discussion, then there is zero net current flow through the coil. Yet, net current is what everyone is measuring. What they are actually measuring is the value of the standing wave current at each end of the coil and it is not flowing. It is only an artifact of the superposition of the two waves that are flowing. The magnitude of the reflected current can be estimated from the feedpoint impedance. The lower the feedpoint impedance, the closer in magnitude is the reflected current to the forward current. For a center-loaded mobile antenna, the reflected current through the coil appears to be well within 5% of the value of the forward current. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
"Frank" wrote As posted in a previous thread go to www.carolyns-creations.com/ve6cb to view the (modeled) current distribution on an 84" monopole at 21.3 MHz. ==================================== Frank, I don't know, and it doesn't matter, how you produced the amperes versus height graph which beautifully displayed itself with a single mouse-click on my computer screen. It displays the curve-shape which any properly educated electrical engineer, or amateur with any intuitive common sense, ought to expect. Thanks! The many reams of heated arguments which have appeared on this newsgroup have been a disgrace to the profession. Yes, I know its an amateur mewsgroup but the (aggressive?) contestents are mostly so-called professionals. Clearly you have chosen an adequate mathematical demonstration model with the ability to use it. Most likely without any thoughts about Terman or theorem-writers Thevenin and Kirchoff, etc., who personally I have hardly ever heard of. If you have not already done so, may I suggest you include radiation resistance in the model for slightly greater accuracy. It may remove the small kink in your curve which occurs immediately at the bottom end of the coil. I don't think it should be there. But further elaboration is hardly worth the effort. I also think its a good idea to base demonstration models (like actual experimental measurements) on the lower frequencies. Try the 160 metre band. They are likely to be more accurate representations. Frank, if you have the time to spare perhaps you should contribute to this newsgroup more often. Improve its already good entertainment, even educational if sometimes confusing, value! By the way, I'm on Dourthe No.1, Bordeaux 2001, tonight. French politics go down very well with their excellent wine and British very mature Cheddar cheese. Hic! ---- Reg, G4FGQ |
Reg Edwards wrote:
By the way, I'm on Dourthe No.1, Bordeaux 2001, tonight. I hear the French are pi$$ed at us for our small boycott of French wine, French vacations, French Fries, etc. :-) Ever notice that us and US mean the same thing for us? -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Cecil Moore wrote:
Reg Edwards wrote: By the way, I'm on Dourthe No.1, Bordeaux 2001, tonight. I hear the French are pi$$ed at us for our small boycott of French wine, French vacations, French Fries, etc. :-) Ever notice that us and US mean the same thing for us? I'm boycotting Texas. No Texas bugcatchers for me, they're unamerican. 73, Tom Donaly, KA6RUH |
Tom Donaly wrote:
I'm boycotting Texas. No Texas bugcatchers for me, they're unamerican. I heard the Texas Bugcatcher guy is an SK so he probably doesn't care. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
W5DXP wrote:
There is forward current flowing into the bottom of the coil and out the top. There is reflected current flowing into the top of the coil and out the bottom. The net current is a standing current wave. In view of the above, for practical putposes, trying to get maximum performance out of the loaded radiator, it should be beneficial to have the same diameter of whip above the coil, rather than tapering whip? One might deduct that if the current is diminishing towards the top, that the diameter of the radiator (RF resistance) could be tapered also. But since the RF current has to flow to the tip and then reflect and go back and interfere with itself, we should make it uniform, where possible. We are probably talking about fraction of a peanut, but for the purists and sake of argument. Yuri, K3BU.us |
"Reg Edwards" wrote in message ... Fact 1. Any loading coil of finite length contributes towards to the total radiation. NEWSFLASH - there's no such thing as a perfect inductor. Amazing! Fact 2. The input and output currents of a loading coil of finite length are always different from each other. A natural consequence of fact #1. Fact 3. The radiation pattern of a short vertical is fixed and remains independent of the location/height of the loading coil. Not so, precisely because said inductor cannot be perfect. HOWEVER, the difference is neglegible and probably immeasureable. Fact 4. Computer programs do not tell gospel truths. They are at least as unreliable as their human programmers. Ahh, but at least they are *consistantly* unreliable in predictable ways, which is more than can be said for humans. ---- Reg. |
Reg Edwards wrote:
. . . Fact 3. The radiation pattern of a short vertical is fixed and remains independent of the location/height of the loading coil. True for practical purposes. People using antenna modeling programs, or people adept with analytical techniques, will find a small difference in pattern as the loading coil is moved, due to the changed current distribution. But it's an inconsequential difference. Roy Lewallen, W7EL |
Yuri Blanarovich wrote:
W5DXP wrote: There is forward current flowing into the bottom of the coil and out the top. There is reflected current flowing into the top of the coil and out the bottom. The net current is a standing current wave. In view of the above, for practical putposes, trying to get maximum performance out of the loaded radiator, it should be beneficial to have the same diameter of whip above the coil, rather than tapering whip? That doesn't help much. What helps is a humongous top hat which does help to equalize the current at the bottom of the coil and the current at the top of the coil. One might deduct that if the current is diminishing towards the top, that the diameter of the radiator (RF resistance) could be tapered also. But since the RF current has to flow to the tip and then reflect and go back and interfere with itself, we should make it uniform, where possible. We are probably talking about fraction of a peanut, but for the purists and sake of argument. Nope, not a fraction of a peanut at all - more like 100% more radiated power because of that humongous top hat. I'm considering a humongous top hat for my pickup that runs the length of the truck and is mounted about a foot above the cab - maybe 50 square feet in all. That would minimize the size of the loading coil and ensure maximum current in the bottom section. The maximum height above ground would be about seven feet, a definite advantage for a mobile antenna around here. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
In view of the above, for practical putposes, trying to get maximum performance out of the loaded radiator, it should be beneficial to have the same diameter of whip above the coil, rather than tapering whip? That doesn't help much. What helps is a humongous top hat which does help to equalize the current at the bottom of the coil and the current at the top of the coil. I know about the effect of hat, but I am refering to straight whip loaded radiator and whip above the coil only. Forget the hats and ties. Again: One might deduct that if the current is diminishing towards the top, that the diameter of the radiator (RF resistance) could be tapered also. But since the RF current has to flow to the tip and then reflect and go back and interfere with itself, we should make it uniform, where possible. (?) Yuri |
Thanks for your comments Reg. The fact is my graph is produced in Excel
from data provided by a NEC 2 output file generated by few trivial lines of NEC code. I cannot claim to have done anything requiring much thought. I just considered, since so much discussion is centered on current distribution, that some might be interested in the posted curves. So far yours is the only response. I will probably delete the page in a day or so. The loading inductor is 2.5" diameter, 6" long, with turns spaced at 0.5". The NEC code is listed on the site, so anybody can copy to verify the validity of my results -- or the validity of the code. I have included a conductivity for copper (5.8001E7 S/m), and since the ground is defined as perfect, this accounts for all losses within the model. The program predicts the total radiated power as 95.918 W from 100 W input. The input current is 2.3874 A RMS, and input impedance 17.545 Ohms. The radiation resistance is therefore 16.829 Ohms. (Sorry for all the decimal places, but they produce such nice round numbers). I was also puzzled by the slight increase in current just under the loading coil, but suspect it was caused by coupling between the lower conductor and the base of the coil. I agree that some experimental data would be good. I have been planning for some time to erect a 160 m vertical, so can see how the predicted results compare. I have also used your software for modeling verticals, and it is in very close to the results produced by NEC. The one problem with NEC 2 (Though not with NEC 4) is that it cannot model buried radials, but can get very close to the ground. I don't mind an occasional post on this news group, but not sure I can contribute much. I do enjoy reading other people's posts though. I sure could enjoy a glass of wine with cheese, but have nothing much in my fridge -- except for some old Cheddar. Regards, Frank "Reg Edwards" wrote in message ... "Frank" wrote As posted in a previous thread go to www.carolyns-creations.com/ve6cb to view the (modeled) current distribution on an 84" monopole at 21.3 MHz. ==================================== Frank, I don't know, and it doesn't matter, how you produced the amperes versus height graph which beautifully displayed itself with a single mouse-click on my computer screen. It displays the curve-shape which any properly educated electrical engineer, or amateur with any intuitive common sense, ought to expect. Thanks! The many reams of heated arguments which have appeared on this newsgroup have been a disgrace to the profession. Yes, I know its an amateur mewsgroup but the (aggressive?) contestents are mostly so-called professionals. Clearly you have chosen an adequate mathematical demonstration model with the ability to use it. Most likely without any thoughts about Terman or theorem-writers Thevenin and Kirchoff, etc., who personally I have hardly ever heard of. If you have not already done so, may I suggest you include radiation resistance in the model for slightly greater accuracy. It may remove the small kink in your curve which occurs immediately at the bottom end of the coil. I don't think it should be there. But further elaboration is hardly worth the effort. I also think its a good idea to base demonstration models (like actual experimental measurements) on the lower frequencies. Try the 160 metre band. They are likely to be more accurate representations. Frank, if you have the time to spare perhaps you should contribute to this newsgroup more often. Improve its already good entertainment, even educational if sometimes confusing, value! By the way, I'm on Dourthe No.1, Bordeaux 2001, tonight. French politics go down very well with their excellent wine and British very mature Cheddar cheese. Hic! ---- Reg, G4FGQ |
According to his website, he is still alive.
Randy |
Frank wrote -
I have also used your software for modeling verticals, and it is in very close to the results produced by NEC. The one problem with NEC 2 (Though not with NEC 4) is that it cannot model buried radials, but can get very close to the ground. ================================ The only program I am reasonably familiar with is the several years old free EZNEC. I don't know whether it has been updated or not and I make very little use of it. Come to think of it, I don't make much use of my own programs either. Regarding shallow buried radials in conjunction with a vertical, have you tried my recent program RADIALS2 ? It is intended to demonstrate performance of the radials themselves in a given ground rather than antenna performance. Which I suspect is the reverse of NEC-4. As you probably know, the effects of above-ground radials change very rapidly as they get within a few inches of the ground surface. But once in the ground they tend to remain static. RADIALS2 uses an entirely different, unconventional form of performance analysis. If other programs don't take soil permittivity into account at HF, predictions must lose accuracy. Are the inputs and outputs of NEC-4 in a form suitable for a direct comparison with my simple program? But in view of the large uncertainties involving ground conditions, accuracy is not worth making much of a song and dance about. ---- Reg, G4FGQ |
"Frank" wrote - I cannot claim to have done anything requiring much thought. I just considered, since so much discussion is centered on current distribution, that some might be interested in the posted curves. So far yours is the only response. ================================== That's because your graph embarasses that half of the contestants who insist the coil's input and output currents are identical and so the less said about it the better. And it gratifies the exhausted sentiments of the other half who are unwilling to grant you the credit for providing the convincing evidence after all the hard work they have put into stating the bleeding obvious. And still are. (After John Cleese who joked about the value of the distinction of a first-class university honours degree in stating the bleeding obvious.) Neither was there was any response to my brief statement of 4 Facts except yours. And for similar reasons. I did not expect any response. But after all, any unsupported statement of mine (no Terman, no Kirchoff, no Kraus, no Thevenin, no Balony) can hardly be construed as evidence of anything. smileysmiley ---- Reg, G4FGQ |
Frank wrote:
So far yours is the only response. Hi Frank, your results look reasonable and thanks for your input. I was also puzzled by the slight increase in current just under the loading coil, but suspect it was caused by coupling between the lower conductor and the base of the coil. A number of us have reported the same thing. In my EZNEC octcoil.ez simulation, (available from my web page below) the net current decreased by 2% from the feedpoint to the coil and then in the first part of the bottom of the coil, it increased by 5%. (Whoops, I almost said it "dropped" by 2% and "rose" by 5% which would have elicited endless nitpicking. :-) There is, no doubt, an impedance discontinuity at each end of the coil. The net current standing-wave values at each end of the coil that differ from just a straight wire are probably due to interference effects among the various forward and reflected wave components. A conceptual idea of what is happening might be the following solvable example (S-parameter analysis). a1-- | --a2 --b1 | b2-- -----Z1-----+-----Z2-----+-----Z3-----open bottom coil top wire wire The Z1 to Z2 impedance discontinuity will cause reflections in both directions. b1 = s11*a1 + s12*a2 b2 = s21*a1 + s22*a2 The Z2 to Z3 impedance discontinuity will also cause reflections in both directions. same equations as above with different parameters The net current at the bottom and top of the coil cannot be expected to be the same as in a straight piece of wire with no step functions in the impedance. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
On Sun, 07 Nov 2004 04:31:00 GMT, "Frank"
wrote: Hi Frank, |Thanks for your comments Reg. The fact is my graph is produced in Excel |from data provided by a NEC 2 output file generated by few trivial lines of |NEC code. I cannot claim to have done anything requiring much thought. I |just considered, since so much discussion is centered on current |distribution, that some might be interested in the posted curves. So far |yours is the only response. I will probably delete the page in a day or so. |The loading inductor is 2.5" diameter, 6" long, with turns spaced at 0.5". |The NEC code is listed on the site, so anybody can copy to verify the |validity of my results -- or the validity of the code. I haven't run your code, but I did something similar, and announced the results here, almost a year ago. Perhaps that explains the lack of response. http://www.qsl.net/n7ws/Loaded%20antennas.htm or in downloadable form: http://www.qsl.net/n7ws/Loaded_Antennas.pdf the antenna files are he http://www.qsl.net/n7ws/AntennaModels.zip Regards, Wes |
Wes Stewart wrote:
I haven't run your code, but I did something similar, and announced the results here, almost a year ago. Perhaps that explains the lack of response. http://www.qsl.net/n7ws/Loaded%20antennas.htm Yet many keep insisting that the net currents at each end of a loading coil are the same magnitude. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Cecil Moore wrote:
Wes Stewart wrote: I haven't run your code, but I did something similar, and announced the results here, almost a year ago. Perhaps that explains the lack of response. http://www.qsl.net/n7ws/Loaded%20antennas.htm Yet many keep insisting that the net currents at each end of a loading coil are the same magnitude. No, "many" don't keep insisting anything of the sort. Those interested should go to Tom Rauch's web site, read everything he wrote on the subject, and come to their own conclusions as to what "many" think. 73, Tom Donaly, KA6RUH |
Tom Donaly wrote:
Cecil Moore wrote: Yet many keep insisting that the net currents at each end of a loading coil are the same magnitude. No, "many" don't keep insisting anything of the sort. Those interested should go to Tom Rauch's web site, read everything he wrote on the subject, and come to their own conclusions as to what "many" think. That's exactly what I am talking about. W8JI completely ignores the increase in current through a loading coil. How does he explain the current inside the coil being of a greater magnitude than anywhere else in the system, including at the feedpoint? (Hint: he doesn't as he apparently believes that would be a violation of Kirchhoff's laws!) But it happens all the time in distributed network configurations. Here's a quote from http://www.w8ji.com "How much difference is there in loading coil current ENTERING the coil and loading coil current EXITING the far end? If the antenna beyond the coil has a low self-impedance compared to the impedance of the shunting capacitance from the coil to "ground", the currents at each end of the coil will be essentially equal." We can imply that w8ji believes that STANDING WAVE currents flow, "ENTERING" the bottom of the coil and "EXITING" the top. With a false premise like that, he cannot possibly get anything right from that point on. However, if we accept Kraus' approximation in the following quote from "Antennas For All Applications", ZERO net current will be flowing through that coil. Speaking of thin linear standing wave antennas: "Current-distribution MEASURMENTS indicate that this is a good assumption provided that the antenna is thin, i.e., when the conductor diameter is less than, say, 0.01WL. Thus, the sinusoidal current distribution approximates the natural (current) distribution on thin antennas." ... "A sinusoidal current distribution may be regarded as the STANDING WAVE produced by two uniform (unattenuated) traveling waves of equal amplitude moving in opposite directions along the antenna." The diameter of #16 wire on 10m is about 0.0001WL, beating Kraus' above approximation requirement by a couple of magnitudes. (The actual difference in the forward current and reflected current through the coil appears to be in the neighborhood of about 5% for a loaded mobile antenna.) -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Unfortunate I have only a NEC 2 based program (Nittany Scientific's NEC-Win
Pro), but with the Sommerfeld/Norton ground model you can approach the ground to within 1/1000 of a wavelength closely approximating the results of buried wires, and in very close agreement with your "RADIALS2" program. NEC programs do require a value for ground permittivity. NEC 4 based software is more expensive, being in the $800.00 range, plus a $500.00 license from the Lawrence Livermore Laboratory. In any case the data are easily compared with your program results. I have measured my ground conductivity, but not yet attempted to measure the permittivity. If anybody wants to get serious with antenna modeling I recommend Ansoft's HFSS (Often known as "Highly Frustrating Structure Simulator"). It costs a mere $30,000, with a $10,000 per year support payment. Regards, Frank "Reg Edwards" wrote in message ... Frank wrote - I have also used your software for modeling verticals, and it is in very close to the results produced by NEC. The one problem with NEC 2 (Though not with NEC 4) is that it cannot model buried radials, but can get very close to the ground. ================================ The only program I am reasonably familiar with is the several years old free EZNEC. I don't know whether it has been updated or not and I make very little use of it. Come to think of it, I don't make much use of my own programs either. Regarding shallow buried radials in conjunction with a vertical, have you tried my recent program RADIALS2 ? It is intended to demonstrate performance of the radials themselves in a given ground rather than antenna performance. Which I suspect is the reverse of NEC-4. As you probably know, the effects of above-ground radials change very rapidly as they get within a few inches of the ground surface. But once in the ground they tend to remain static. RADIALS2 uses an entirely different, unconventional form of performance analysis. If other programs don't take soil permittivity into account at HF, predictions must lose accuracy. Are the inputs and outputs of NEC-4 in a form suitable for a direct comparison with my simple program? But in view of the large uncertainties involving ground conditions, accuracy is not worth making much of a song and dance about. ---- Reg, G4FGQ |
Cecil,
You appear to have some unique views of superposition and of standing waves. In simple terms superposition says that one can combine two inputs, and the combined output is equal to the sum of the individual outputs. Not all systems exhibit superposition, of course, but I believe the elementary antennas considered here do indeed follow the principle of superposition with regard to current. Why do you believe the "net" current somehow has different properties than simply the sum of the two component traveling current waves? You use the term "artifact", as if the net current is inconsequential or even incorrect. Does superposition break down? Distributed network vs. DC or AC model is not an issue, since the superposition must be performed independently at each point in the region of interest. (You seem to like to use "net", but "total" or "algebraic sum" mean the same thing. I am not interested in any argument about performing the vector math correctly. That must be assumed.) Standing waves are not static. The current may not "flow", whatever that means, but there is certainly real non-zero current at every point except the exact nodes of the standing wave. If you prefer, the standing wave current oscillates rather than flows, but that is of no special importance here. Why do you believe standing waves are somehow inferior to traveling waves? (This message is absolutely serious. No tricks or trolling. If you want to play word games, see ya later.) 73, Gene W4SZ Cecil Moore wrote: There is forward current flowing into the bottom of the coil and out the top. There is reflected current flowing into the top of the coil and out the bottom. The net current is a standing current wave. If we, as Kraus suggests, assume that the forward current equals the reflected current (relatively small error in doing so) then there is zero net current flowing in and out of the coil. The standing wave current is, well, just standing there and is not "going" anywhere. The gross error that a lot of people are making is that standing wave current flows. If the forward and reflected currents are equal, as Kraus assumes for purpose of discussion, then there is zero net current flow through the coil. Yet, net current is what everyone is measuring. What they are actually measuring is the value of the standing wave current at each end of the coil and it is not flowing. It is only an artifact of the superposition of the two waves that are flowing. |
"Wes Stewart" wrote in message ... On Sun, 07 Nov 2004 04:31:00 GMT, "Frank" wrote: Hi Frank, |Thanks for your comments Reg. The fact is my graph is produced in Excel ...... |...........validity of my results -- or the validity of the code. I haven't run your code, but I did something similar, and announced the results here, almost a year ago. Perhaps that explains the lack of response. http://www.qsl.net/n7ws/Loaded%20antennas.htm or in downloadable form: http://www.qsl.net/n7ws/Loaded_Antennas.pdf the antenna files are he http://www.qsl.net/n7ws/AntennaModels.zip Regards, Wes Thanks for the information Wes. I have only recently noticed the loading coil discussions going on, so guess I missed a lot of the earlier postings. Your curves are very similar to mine, although I plotted only those currents within the loading coil, that are spaced by the winding separation (Which happens to be the same as the overall segmentation). The far field is proportional to the portion of the current (within the helix) in the "z" direction, and assume that the x and y components are cancelled out. Such plotting seems to be supported by computing the integral of I(z)dz -- while realizing the limitation of such expressions. I just tried to run your EZNEC files, but cannot since I only have the demo program. Will have to figure out a way to extract the NEC code. The qsl.net site is incredibly slow, I had to make a couple of attempts to download your files. Regards, Frank |
Gene Fuller wrote:
Why do you believe the "net" current somehow has different properties than simply the sum of the two component traveling current waves? Because the net current is a *STANDING WAVE* made up of equal magnitudes of current flowing in opposite directions. That makes the net current zero, Gene. Standing wave current doesn't flow. The RMS value stands still. Standing waves are only an artifact of the superposition process. Everything that needs to be known involves the two traveling waves that cause the standing wave. Asserting that standing waves flow into the bottom of a loading coil and out the top shows a complete ignorance of how standing wave antennas really work. After that false premise, none of the associated conclusions are valid. Standing waves are not static. The RMS value of a standing wave at any point is indeed static. The current may not "flow", whatever that means, but there is certainly real non-zero current at every point except the exact nodes of the standing wave. If you prefer, the standing wave current oscillates rather than flows, but that is of no special importance here. It is of infinite importance. If the standing wave current oscillates in place, it doesn't flow through the coil. W8JI says it flows into the bottom of the coil and out the top. Nothing could be farther from the facts of physics. Why do you believe standing waves are somehow inferior to traveling waves? Standing waves are an artifact of the superposition of two traveling waves. Standing waves have a constant differing RMS value at every point on the transmission line. Traveling waves travel and have the same RMS value all up and down a lossless transmission line. What is it about that concept that you don't understand? -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Cecil,
Thanks. I thought I understood the situation. Now I am certain. Bye. :-) 73, Gene W4SZ Cecil Moore wrote: Gene Fuller wrote: Why do you believe the "net" current somehow has different properties than simply the sum of the two component traveling current waves? Because the net current is a *STANDING WAVE* made up of equal magnitudes of current flowing in opposite directions. That makes the net current zero, Gene. Standing wave current doesn't flow. The RMS value stands still. Standing waves are only an artifact of the superposition process. Everything that needs to be known involves the two traveling waves that cause the standing wave. Asserting that standing waves flow into the bottom of a loading coil and out the top shows a complete ignorance of how standing wave antennas really work. After that false premise, none of the associated conclusions are valid. Standing waves are not static. The RMS value of a standing wave at any point is indeed static. The current may not "flow", whatever that means, but there is certainly real non-zero current at every point except the exact nodes of the standing wave. If you prefer, the standing wave current oscillates rather than flows, but that is of no special importance here. It is of infinite importance. If the standing wave current oscillates in place, it doesn't flow through the coil. W8JI says it flows into the bottom of the coil and out the top. Nothing could be farther from the facts of physics. Why do you believe standing waves are somehow inferior to traveling waves? Standing waves are an artifact of the superposition of two traveling waves. Standing waves have a constant differing RMS value at every point on the transmission line. Traveling waves travel and have the same RMS value all up and down a lossless transmission line. What is it about that concept that you don't understand? |
Gene Fuller wrote:
I thought I understood the situation. Now I am certain. Hopefully, we can lay this thing to rest soon. The forward current flows into the bottom of the coil and out the top. The reflected current flows into the top of the coil and out the bottom. Those two currents are very close to being equal magnitudes but their phases are rotating in opposite directions. That is not a job for the lumped circuit model. That's a job for the distributed network model, something that you guys seem to have first ignored and later tried to sweep under the rug. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Gene, W4SZ wrote:
"Standing waves are not static." Incredible! My "American College dictionary" defines "standing wave": "a distribution of wave displacements , such that the distribution in space is periodic, with fixed maximum and minimum points, with the maxima occuring everywhere at the same time, as in vibration of strings, electric potentials, acoustic pressures, etc." Note the word "fixed" in the definition. That`s a synonym for "static". For how this applies to antennas and transmission lines, see page 177 of Kraus` "Antennas", third edition, Figure 6-7. Notice that current reverses 1/2-wavelength back from the antenna`s open-circuit endjust as it does in the case of the open-circuit transmission-line, as shown by Terman on page 92 of "Electronic and Radio Engineering", 1955 edition, and on page 94 in FiG. 4-5 (a). This all starts at the reflection point and progresses the same regardless of the length of the antenna or transmission-line. It is due to superposition of the forward and reflected waves, just as Cecil maintains. Advice: Never argue with Kraus and Terman. Best regards, Richard Harrison, KB5WZI |
"Cecil Moore" wrote in message ... Reg Edwards wrote: By the way, I'm on Dourthe No.1, Bordeaux 2001, tonight. I hear the French are pi$$ed at us for our small boycott of French wine, French vacations, French Fries, etc. :-) Ever notice that us and US mean the same thing for us? -- 73, Cecil http://www.qsl.net/w5dxp Don't know if it is true, but I heard that France had a problem that wiped out one type or area of grapes and they imported some of the same type from the U.S. True? 73, -- Steve N, K,9;d, c. i My email has no u's. |
Steve Nosko wrote:
"Cecil Moore" wrote in message ... Reg Edwards wrote: By the way, I'm on Dourthe No.1, Bordeaux 2001, tonight. I hear the French are pi$$ed at us for our small boycott of French wine, French vacations, French Fries, etc. :-) Ever notice that us and US mean the same thing for us? -- 73, Cecil http://www.qsl.net/w5dxp Don't know if it is true, but I heard that France had a problem that wiped out one type or area of grapes and they imported some of the same type from the U.S. True? 73, The French wine industry was decimated in the 19th century by a phylloxera infestation from America. The problem was solved by using native American root stock onto which French grape vines were grafted. Most wine grapes in America have European ancestry. I doubt whether there's a grape vine in the world that cares who is president of the U.S. 73, Tom Donaly, KA6RUH |
Tom Donaly wrote:
I doubt whether there's a grape vine in the world that cares who is president of the U.S. The grapevine around Madison County, TX was buzzing with the news of Bush's re-election on the morning of Nov. 3. |
Richard,
I am quite familiar with standing waves, thank you. I have no disagreements with Terman, Kraus, Balanis, or any other legitimate experts. You can reread what I said, if you care to understand, rather than pick a sentence out of context. 73, Gene W4SZ Richard Harrison wrote: Gene, W4SZ wrote: "Standing waves are not static." Incredible! My "American College dictionary" defines "standing wave": "a distribution of wave displacements , such that the distribution in space is periodic, with fixed maximum and minimum points, with the maxima occuring everywhere at the same time, as in vibration of strings, electric potentials, acoustic pressures, etc." Note the word "fixed" in the definition. That`s a synonym for "static". For how this applies to antennas and transmission lines, see page 177 of Kraus` "Antennas", third edition, Figure 6-7. Notice that current reverses 1/2-wavelength back from the antenna`s open-circuit endjust as it does in the case of the open-circuit transmission-line, as shown by Terman on page 92 of "Electronic and Radio Engineering", 1955 edition, and on page 94 in FiG. 4-5 (a). This all starts at the reflection point and progresses the same regardless of the length of the antenna or transmission-line. It is due to superposition of the forward and reflected waves, just as Cecil maintains. Advice: Never argue with Kraus and Terman. Best regards, Richard Harrison, KB5WZI |
Gene Fuller wrote:
I am quite familiar with standing waves, thank you. I have no disagreements with Terman, Kraus, Balanis, or any other legitimate experts. Question is: Why do you promote W8JI's stuff when it is quite obvious that he is NOT familiar with standing waves. If he were familiar with standing waves, he wouldn't be asserting that net standing wave current flows into the bottom of the loading coil and out the top of the loading coil. Are you absolutely sure that you want to promote the alleged "information" on W8JI's web page as absolute fact? If he is so right and so capable of defending his assertions, why isn't he here right now? (Trying to get W8JI to follow me down the Primrose Path :-) as he did when he asserted that "differential" effects are "completely unrelated" to "common mode" effects.) -- 73, Cecil, W5DXP |
Reg Edwards wrote:
The only program I am reasonably familiar with is the several years old free EZNEC. I don't know whether it has been updated or not and I make very little use of it. Come to think of it, I don't make much use of my own programs either. Regarding shallow buried radials in conjunction with a vertical, have you tried my recent program RADIALS2 ? It is intended to demonstrate performance of the radials themselves in a given ground rather than antenna performance. Which I suspect is the reverse of NEC-4. As you probably know, the effects of above-ground radials change very rapidly as they get within a few inches of the ground surface. But once in the ground they tend to remain static. RADIALS2 uses an entirely different, unconventional form of performance analysis. If other programs don't take soil permittivity into account at HF, predictions must lose accuracy. Are the inputs and outputs of NEC-4 in a form suitable for a direct comparison with my simple program? Yes. I made a few comparisons long ago, shortly after you introduced your program, and found major disagreement. NEC-4 approximately agrees with the measurements made long ago by Brown, Lewis, and Epstein (whom I know you've never heard of), once you make reasonable assumptions of ground conductivity and dielectric constant. Your program gives very different answers. At the time, I concluded that there's considerable coupling between radials, which your program doesn't seem to account for. Interested readers should look in the google archives for postings in this group on the thread "Ground Radials" in July 1998 and "Evaluation of G4FGQ Freeware Antenna Software" in September 1998. But in view of the large uncertainties involving ground conditions, accuracy is not worth making much of a song and dance about. True, but in the past, you've used the results from your program to reach conclusions about radial systems that I didn't, and don't, believe to be valid. (See the threads mentioned above.) I don't think it's wise to draw conclusions from a program that gives results which are demonstrably very different from the only measurements regarded to be reasonably well made. Roy Lewallen, W7EL |
"Roy Lewallen" wrote in message ... Reg Edwards wrote: The only program I am reasonably familiar with is the several years old free EZNEC. I don't know whether it has been updated or not and I make very little use of it. Come to think of it, I don't make much use of my own programs either. Regarding shallow buried radials in conjunction with a vertical, have you tried my recent program RADIALS2 ? It is intended to demonstrate performance of the radials themselves in a given ground rather than antenna performance. Which I suspect is the reverse of NEC-4. As you probably know, the effects of above-ground radials change very rapidly as they get within a few inches of the ground surface. But once in the ground they tend to remain static. RADIALS2 uses an entirely different, unconventional form of performance analysis. If other programs don't take soil permittivity into account at HF, predictions must lose accuracy. Are the inputs and outputs of NEC-4 in a form suitable for a direct comparison with my simple program? Yes. I made a few comparisons long ago, shortly after you introduced your program, and found major disagreement. NEC-4 approximately agrees with the measurements made long ago by Brown, Lewis, and Epstein (whom I know you've never heard of), once you make reasonable assumptions of ground conductivity and dielectric constant. Your program gives very different answers. At the time, I concluded that there's considerable coupling between radials, which your program doesn't seem to account for. Interested readers should look in the google archives for postings in this group on the thread "Ground Radials" in July 1998 and "Evaluation of G4FGQ Freeware Antenna Software" in September 1998. But in view of the large uncertainties involving ground conditions, accuracy is not worth making much of a song and dance about. True, but in the past, you've used the results from your program to reach conclusions about radial systems that I didn't, and don't, believe to be valid. (See the threads mentioned above.) I don't think it's wise to draw conclusions from a program that gives results which are demonstrably very different from the only measurements regarded to be reasonably well made. Roy Lewallen, W7EL ============================== Roy, it's gratifying to see, once again, you take notice of my sayings. Such as, I repeat - "Fact 4. Computer programs do not tell gospel truths. They are at least as unreliable as their human programmers." ---- Reg. |
Steve Nosko wrote:
"Play with words if U like." The whole phenomenon is not static. The incident and reflected waves move. It is their interference patterns, the standing waves, which are static. Cecil wisely called them the rms values. I assumed it understood that the RF (a-c) voltages and currents are expressed as their rms values unless otherwise specified. Everyone should know that a-c is an acronym for alternating current which, of course, alternates, Best regards, Richard Harrison, KB5WZI |
Modeled #14 AWG, copper conductor, 32ft monopole, 29 radials of 25ft, and
base 6" above (nominal lambda/1000) Sommerfeld/Norton ground of Er = 13, sigma = 0.013 S/m at 1.8 MHz. All segments 6". NEC2 computes: Zin = 2.87 - j1358 Efficiency 92% RADIALS2 computes (with radials 1mm below ground): Zin = 1.55 - j1310 Efficiency 23.5% Not a large amount of difference, but thought I had gotten closer results with a different monopole, but seem to have deleted the code (Not sure why such a large difference in efficiency). NEC2 is supposed to provide a reasonable approximation of a buried radial monopole when at about lambda/1000 above ground. Be interested in any comments, and what NEC4 provides if anybody has it. 73, Frank "Roy Lewallen" wrote in message ... Reg Edwards wrote: The only program I am reasonably familiar with is the several years old free EZNEC. I don't know whether it has been updated or not and I make very little use of it. Come to think of it, I don't make much use of my own programs either. Regarding shallow buried radials in conjunction with a vertical, have you tried my recent program RADIALS2 ? It is intended to demonstrate performance of the radials themselves in a given ground rather than antenna performance. Which I suspect is the reverse of NEC-4. As you probably know, the effects of above-ground radials change very rapidly as they get within a few inches of the ground surface. But once in the ground they tend to remain static. RADIALS2 uses an entirely different, unconventional form of performance analysis. If other programs don't take soil permittivity into account at HF, predictions must lose accuracy. Are the inputs and outputs of NEC-4 in a form suitable for a direct comparison with my simple program? Yes. I made a few comparisons long ago, shortly after you introduced your program, and found major disagreement. NEC-4 approximately agrees with the measurements made long ago by Brown, Lewis, and Epstein (whom I know you've never heard of), once you make reasonable assumptions of ground conductivity and dielectric constant. Your program gives very different answers. At the time, I concluded that there's considerable coupling between radials, which your program doesn't seem to account for. Interested readers should look in the google archives for postings in this group on the thread "Ground Radials" in July 1998 and "Evaluation of G4FGQ Freeware Antenna Software" in September 1998. But in view of the large uncertainties involving ground conditions, accuracy is not worth making much of a song and dance about. True, but in the past, you've used the results from your program to reach conclusions about radial systems that I didn't, and don't, believe to be valid. (See the threads mentioned above.) I don't think it's wise to draw conclusions from a program that gives results which are demonstrably very different from the only measurements regarded to be reasonably well made. Roy Lewallen, W7EL |
"Frank" wrote in message news:H4hkd.141267$9b.112169@edtnps84... Modeled #14 AWG, copper conductor, 32ft monopole, 29 radials of 25ft, and base 6" above (nominal lambda/1000) Sommerfeld/Norton ground of Er = 13, sigma = 0.013 S/m at 1.8 MHz. All segments 6". NEC2 computes: Zin = 2.87 - j1358 Efficiency 92% RADIALS2 computes (with radials 1mm below ground): Zin = 1.55 - j1310 Efficiency 23.5% Not a large amount of difference, but thought I had gotten closer results with a different monopole, but seem to have deleted the code (Not sure why such a large difference in efficiency). NEC2 is supposed to provide a reasonable approximation of a buried radial monopole when at about lambda/1000 above ground. Be interested in any comments, and what NEC4 provides if anybody has it. 73, Of course the higher efficiency is due to NEC calculating only the I^2R losses, and not the TRP. TRP should be fairly easy to calculate since the pattern is "phi" independent. Have not checked to see if there is a TRP card. Note that a 32 ft monopole mounted on a perfect ground has an input impedance of 1.58 - j1311 Ohms. The efficiency is reduced to 86% due to increased I^2R losses. Frank |
Gene Fuller wrote:
I am quite familiar with standing waves, thank you. I have no disagreements with Terman, Kraus, Balanis, or any other legitimate experts. What I am still not understanding, is since the exponential equations for voltage and current in a transmission line are identical except for the Z0 term, how can something happen to the current without the same thing happening to the voltage at the same time? How can something happen to the voltage without also happening to the current at the same time? In a matched system, the voltage and current arrives at the load at exactly the same time attenuated by exactly the same amount. But that voltage didn't flow and that current didn't drop??? -- 73, Cecil, W5DXP |
On Thu, 11 Nov 2004 18:46:18 -0600, Cecil Moore
wrote: the voltage and current arrives at the load at exactly the same time Only if you skip a battery off someone's skull. |
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