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Roy Lewallen wrote:
Now, that's quite an insult, based on a total lack of information about my career and what I've accomplished. I freely admit that there was absolutely no truth or validity to the insult. It was a less than subtle response to your subtle put-downs of some engineers whose thoughts, style, and results differs from yours. An appropriate response was difficult to gage. I'm not very subtle and I apologize if the magnitude of my response was unjustified. To all readers of this newsgroup: I have been an admirer and supporter of Roy's contributions to amateur radio for decades and I will continue to be. This is a public apology. Roy doesn't really remind me of that engineer who used to work for me. -- 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! =----- |
To all readers of this newsgroup: I have been an admirer and supporter of Roy's contributions to amateur radio for decades and I will continue to be. This is a public apology. Roy doesn't really remind me of that engineer who used to work for me. -- 73, Cecil http://www.qsl.net/w5dxp Same here, ditto! Just that one would expect from a person like that to be more open minded and less infected by W8JI/G4FGQ (ridiculing absolute knowitalls) virus. We live, learn and still die stupid (who said that? :-) Yuri |
Cecil, W5DXP wrote:
"---isn`t everything moot after Kraus tells us that the antenna coil can cause a 180 degree phase reversal?" Yes. The Kraus example is a resonant circuit of a coil which with its inherent self capacitance which can produce a leading or lagging total impedance, depending on frequency. B. Whitfield Griffith, Jr. demonstrates this with a series LRC circuit on page 108 of "Radio-Electronic Transmission Fundamentals". Total impedance, Zt = R+jomegaL-J/omegaC. Griffith tabulates ZL, ZC, and Zt for 2.4, 2.5, 2.6, 2.7, and 2.8 MHz. R=30 ohms at all frequencies. 2.4 MHz, j226ZL, -265ZC, 30-j39Zt 2.5 MHz, j236ZL, -j255ZC, 30-j19Zt 2.6 MHz, j245ZL, -j245ZC, 30-j0Zt 2.7 MHz, j254ZL, -j236ZC, 30+j18Zt 2.8 MHz, j264ZL, -j227ZC, 30+j37Zt Griffith also gives Zt in polar coordinates but I don`t need to copy that to show that reactance can be either positive or negative in a circuit with both inductance and capacitance. Best regards, Richard Harrison, KB5WZI |
"Roy Lewallen" wrote in message ... Are you going to insist that it be one of these ferrite core jobs, or is it more like ones on a HF6V? Is there something about a "ferrite job" that makes it follow different rules? But the answer is no to both. I insist on using a physically small toroid wound on a powdered iron core. Only after people understand how a physically small inductor works will they have any chance of understanding how a physically long one does. The discussion is about 'long' inductors. You continue to try to steer the discussion away from them. Why is that? 73, Jim AC6XG |
"Cecil Moore" wrote in message ... Reg Edwards wrote: A design which 'exceeds' specified performance is as poor as one which 'under exceeds'. It would have cost money and space to add the circuits to bring the measurable jitter up to the RS232 specification allowable threshold. You really think I should have done that? Designs which overachieve are an embarrassment to the proletariat, and are to be discouraged. 73, ac6xg |
Yuri Blanarovich wrote:
We live, learn and still die stupid (who said that? :-) Einstein, in so many words. -- 73, Cecil http://www.qsl.net/w5dxp "One thing I have learned in a long life: that all our science, measured against reality, is primitive and childlike ..." Albert Einstein -----= 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! =----- |
Roy Lewallen wrote:
For anyone who cares, the magnitude of the current out of the inductor in the later test measured 5.4% less than the current in. That would be one amp in and 0.9460 amps out. The angle whose cosine is 1 is zero deg. The angle whose cosine is 0.9460 is 18.9 degrees. So Yuri's estimate of an 18 degree effect was pretty accurate. -- 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! =----- |
Roy Lewallen wrote in message ...
Ok, For anyone who cares, the magnitude of the current out of the inductor in the later test measured 5.4% less than the current in. No phase shift was discernible. An analytical person could build on this information to investigate the properties of longer inductors placed elsewhere in the antenna. Thank you for the comments, Cecil, Yuri, Richards, Art, and others. I've learned a good lesson from this -- that this isn't an appropriate forum or appropriate audience for the sort of quantitative analysis and reasoning I'm familiar and comfortable with. And that the considerable time and effort required to make careful measurements is really of very little benefit -- certainly not anywhere near enough to justify it. Interesting though. I think I may try to rig up some couplers so I can do this myself. I have the dual channel scope, but I need to build the couplers. With a great sigh of relief from everyone, I'm sure, I'll now turn this thread back over to Yuri, Cecil, et al. My apologies to everyone for taking up so much bandwidth. None needed. If the group can have multiple postings on amateur racists, and other assorted problem children, then I see no problem with this thread, no matter how long it gets. So far, your tests, while not being a bugcatcher type coil seem to match my expectations fairly closely. I never expected to see no reduction at all. In my view, even a large 75m bugcatcher coil is still a lumped coil, and will pretty much act as one. Why do I think this? Because the overall form is still very small per wavelength. IE: 90 degrees is appx 65 ft. So far no one has argued that the current taper UNDER the coil is suspect when modeled. Most all seem to agree that the current distribution is dramatically improved when the coil is raised up the mast. If you model a 10 ft whip, using a center load coil, the model will show max current at the coil. Here is an example using eznec.... EZNEC Demo ver. 3.0 Vertical over real ground 11/12/03 11:30:20 AM --------------- CURRENT DATA --------------- Frequency = 3.85 MHz. Wire No. 1: Segment Conn Magnitude (A.) Phase (Deg.) 1 Ground 1 0.00 2 1.0013 -0.01 3 1.0036 -0.02 4 1.0072 -0.03 5 1.0122 -0.04 6 1.0192 -0.04 7 1.029 -0.05 8 1.0432 -0.06 9 1.0691 -0.06 10 1.1036 -0.07 ......coil is at segment 10 11 .98384 -0.07 12 .87242 -0.07 13 .77233 -0.07 14 .67604 -0.07 15 .58163 -0.07 16 .48789 -0.08 17 .3938 -0.08 18 .2982 -0.08 19 .19932 -0.08 20 Open .08787 -0.08 OK. Lets say the coil in the real world is one foot long. That is appx 1/10 of the total antenna length. Will there be any argument that max current will occur at the coil? I hope not... OK. Lets say that Yuri, et el, are correct and there is a noticable taper of current across the coil from bottom to top. I still think they are being fooled by the capacitance above the coil, which is where they are testing, but thats another issue. Say you have a 1 ft section of the antenna, "coil" and it is found that there is a noticable current taper across it. What would this amount to in the real world? To me, nothing much at all. I don't think it would have any effect on the way I build mobile antennas. It won't have any effect on where I mount my coil, because I am already using the best locations possible. These "best" coil locations are old news and easily calculated using a program such as Reg's "vertload" or even info in the ARRL antenna handbook. Would this current taper in a 1/10 section of the antenna drastically skew any modeling done of this antenna? It's possible, but again, I really doubt it. BTW, I think I said earlier that the modeling of these mobile whips didn't do a good job of showing increases in performance due to changes in coil position. But that seems to not be the case. I may have been thinking of something else. I do show increases in gain when the coil is raised from a base load, to a center load. As far as the reflected currents, and phase, etc, I just don't see that causing a major difference in the current across the coil. Some difference I'm sure, but I don't think it would be enough to cause a difference in either the calculation of best coil location, or in the modeling of the antenna. I'm still of the opinion that if you measure the current at the top of the coil, where it is attached to the capacitance section, this will slightly stunt the upper coil measurement. The eznec plot *seems* to agree. I'm still of the opinion that the current is *fairly* constant across the coil, but I'm not losing any sleep over it. I'll still be building my antennas the same way I have been. Nothing will change, even if it's determined they are correct about this current taper across the coil. MK |
"Roy Lewallen" wrote in message ... Do we agree that the amount of differential will depend on the number of 'degrees missing' from the length of the antenna? No. In a few minutes, I'll post a description of a more recent measurement I made that refutes this. Of course, elementary circuit theory refutes it also, which is the basis for my disagreement. Perhaps the statement was poorly worded. The presumption is that the "missing degrees" of length are supplied by the coil. Do you believe this is untrue? Realize of course, that a sufficiently simple model can fail to describe any phenomenon which has been oversimplified in the model. Do we agree that the position of the loading coil plays a significant. role in determining how much of a current differential will appear across it? If you're talking about a physically long coil, yes. If you're talking about a physically small coil, no. Yes, Roy. The discussion is limited to those coils which cause a current differential from one end to the other. The other kind don't meet the requirement. :-) But if you believe that the amount of antenna the coil "replaces" determines the differential, wouldn't this be true regardless of the placement of the coil in the antenna? No. Note the shape of the current vs position curve along the antenna. It doesn't change linearly with position. There are relatively flat regions near the ends, and there's region nearer the middle where the current changes rapidly with position. Presumably it's related to the way the impedance changes with position along the antenna. Are you going to insist that it be one of these ferrite core jobs, or is it more like ones on a HF6V? Is there something about a "ferrite job" that makes it follow different rules? The 'ferrite jobs' provide considerably more inductance for a given coil size. Fewer turns, shorter length of wire, physically smaller, no radiation. Do you agree there's a difference between air and ferrite? Only after people understand how a physically small inductor works will they have any chance of understanding how a physically long one does. Which people are those, Roy? 73, Jim AC6XG |
"Mark Keith" wrote in message
om... So far, your tests, while not being a bugcatcher type coil seem to match my expectations fairly closely. I'd like to hear an explanation for ANY current difference across a coil that is supposedly behaving as a lumped inductor. But the test really should be for the same type of antenna used in Yuri's discussion; A physically short antenna, with an electrically long coil, positioned away from the feedpoint. One misconception here has been about the physical length of the coil with respect to wavelength. That's not the most relevant issue, in my opinion. The wire comprising the coil also has a physical length. The relationship between physical length and electrical length is velocity factor. The same thing is true for a coil. The velocity factor for a wire does not go to infinity simply by virtue of the fact that it has been wound into a coil. This is basically what is being implied when someone argues that loading coils do not effectively supliment the electrical length of an antenna. 73, Jim AC6XG |
Cecil Moore wrote in message ...
Yuri Blanarovich wrote: What's this guessing game anyway? If you can talk an astronomer into predicting the day in 2004 when the first level 3 solar storm will hit earth, you can discredit him when his prediction falls through. More thoughts from the rubber room...Lets say you, Yuri and crew are correct and the current taper is large across the coil. Lets say the coil is still a 1 ft long bugcatcher coil. Lets say the current is fairly constant below the coil. What will the real world effect be of this phenomenon? About the same as using a shorter coil, the way I see it. The current below the coil should still be appx the same. The coil location has not moved. All you might see is a beginning of current taper of appx 2-4-6 inches lower than you might normally expect. What will be the effect of this? Hardly nada I suspect. But lets take this to a further gross level. Lets drop the coil from 47.5% above base, to 37.5% above base. Will all surely agree this would be a worse case to performance than any severe taper of current in the coil? What do I see when modeling? -1.75 dbi vs -1.96 dbi. I think this discrepancy would be as bad as you would ever see from a taper of current across a coil. Even if the coil was a foot long or longer, as long as you don't approach a helical antenna. I can't normally hear .21 db difference. But lets take this even farther and use vertload. I tried an appx 10 ft antenna with a coil 1.44 m above base, with a 1.5 m stinger. The radiating efficiency was 17.58 db using 4 ohms for ground loss, with a 1.3 db hit compared to a 1/4 wave. I then dropped the coil to 1.14 m above base, and lengthened the stinger to 1.8 m. 15.95 db efficiency with the same 1.3 db hit compared to a 1/4 wave. I assume this difference to be as bad and most likely worse than any error shown from a current taper across the coil when modeling or in the real world. To *me*, I find it all pretty much a non issue, and basically a turd hunt as we call it down here in redneck country. But this is not to say I don't admire the determination and grit of the participants involved in this episode of "A Current Affair". But what do I know...They don't keep me in a rubber room for nothing... MK |
On 11-Nov-2003, Roy Lewallen wrote: My apologies to everyone for taking up so much bandwidth. 73, Roy Lewallen, W7EL Roy, Your postings are never a waste of bandwidth. I hope that you plan to publish more of the type of experiments which you have just described. I believe your methods are brilliant examples of both the scientific method and good engineering practice. Bravo Zulu! KO6NO |
Mark Keith wrote:
So far, your tests, while not being a bugcatcher type coil seem to match my expectations fairly closely. They seem to have matched Yuri's predictions almost exactly. He predicted a 5% reduction in current. That was very close. He predicted an 18 degree effect. Turns out a 5% reduction in current in that area of the cosine curve is almost exactly 18 degrees. Cos-1(.95) = 18 degrees -- 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:
Perhaps the statement was poorly worded. The presumption is that the "missing degrees" of length are supplied by the coil. Do you believe this is untrue? Realize of course, that a sufficiently simple model can fail to describe any phenomenon which has been oversimplified in the model. Roy's measurements verify Yuri's predictions. Assuming 1.0 amps at zero degrees on one side of the coil, 0.95 amps out is almost exactly 18 degrees since arc-cos(0.95)=18.2 degrees. Am I missing something? -- 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:
I'd like to hear an explanation for ANY current difference across a coil that is supposedly behaving as a lumped inductor. But the test really should be for the same type of antenna used in Yuri's discussion; Jim, did you fail to notice that arc-cos(0.95) = 18.2 degrees? -- 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! =----- |
Mark Keith wrote:
More thoughts from the rubber room...Lets say you, Yuri and crew are correct and the current taper is large across the coil. Lets say the coil is still a 1 ft long bugcatcher coil. Lets say the current is fairly constant below the coil. What will the real world effect be of this phenomenon? Roy's measurements vindicated Yuri's prediction. Current in equals 1.0 amp at zero degrees. Measured current out equals 0.95 amps. arc-cos(0.95) = 18 degrees. Yuri's prediction was right on. What else is there to argue about? Even the small toroidal coil functioned exactly as predicted by Yuri. -- 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! =----- |
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Richard KB7QHC wrote:
I offered an EZNEC analysis that supported (circumspectly) Yuri's position, but he blew it off chasing rainbows. I am terribly sorry, with all the mumbo-jumbo going on I didn't see the right rainbow over the devils :-) I have to go back and reread the thread (take a vacation :-), I guess some of the points obvious to me that were nit picked blinded me over the diamonds hidden. The confusion was that all I had on the W9UCW set up was what I had published, and you assumed that was my setup/data and kept asking me about it. I will be making snap-on current probe, which will make it easier to slide along the element and observe the current without the disturbance to the antenna and will be a bit different over the thermocouple meters. Just need a bit more time. Thanks to all those civil pros and cons, looks like we are getting ahead. If we can implements the phenomena properly in modeling software, it should be giant step in properly analyzing and designing loaded antennas and elements. There are many dBs hidden there. Yuri, K3BU/m |
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Richard,
If your current is different at the ends of the coil, you're an angel. The question that leaps to mind is how are you going to replicate the data if you were so ignorant of the original details? Even more, it would further all discussion for you to offer a COMPLETE specification of what you are doing (or going to do), rather than an informal ramble around the garden with a camera. The point of the original argument was: is the current the same or different at the ends of the typical coil in loaded antenna. I will reiterate the exercise: I knew it was different from my "heat tests with Hustler", W8JI countered "you dummy, it can't be" (in a nutshell :-), ON4UN showed graphically how, W9UCW chimed in "it is, I measured it, here is some data", Cecil theorized it, W8JI chorus "calculated" it can't be. My point is that I argued that current is different, not how precisely I can calculate or offer calculated "proof", the first order was to convince unbelievers that there is a difference and let them loose to figure out why (Cecil shined light on it) and then to properly apply formulas and figures so we can model it. So when I say that I want to do MY measurements, I am not after exactly duplicating W9UCW measurements and test, I just want to pick, first my mobile antenna (practical situation) and then similar setup what Barry used - nice 60 radial ground plane and various loaded radiators and see what (formulas, software) comes close to reality. We are already seeing some path, and with sliding current probe I believe I can get more data along the radiators and we can see how does it jive with Barry's and with calculations and modeling. So again, I am not after replicating Barry's laboratory. If what we are saying is true, than it doesn't matter how fat the coil is, where it is within the limits, more data from various situations will help us to correlate the procedures. My goal was to convince unbelievers (and as we can see, there are plenty), well, to show that current in a typical loading coil's ends IS DIFFERENT (it is up them to believe it or not). This wasn't on the level of scientific conference paper, but more like a street fight - who is right and why are you ridiculing me (us) if I am (we are) right. Now roll your slide rule blades out and lets do the stage two, fine tune the "theory" and put some good numbers on IT. So she's round after all? Should we change thread name now? Yuri, K3BU.us |
Yuri Blanarovich wrote:
So when I say that I want to do MY measurements, I am not after exactly duplicating W9UCW measurements and test, I just want to pick, first my mobile antenna (practical situation) and then similar setup what Barry used - nice 60 radial ground plane and various loaded radiators and see what (formulas, software) comes close to reality. Why bother, Yuri? Roy proved your predictions to be right on. His physically small inductance had almost exactly an 18 degree effect just as you predicted. -- 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! =----- |
Why bother, Yuri? Roy proved your predictions to be right on. His physically small inductance had almost exactly an 18 degree effect just as you predicted. -- 73, Cecil http://www.qsl.net/w5dxp I want to see how well can we track modeling, and what is the proper way to model the inductors and "force" the Eznec et al to tell the truth? Back to the behavior of coils and RF current distribution, isn't the same thing happening in a PI tank of amplifiers? At one end we have hi impedance (tube side) low current, at the antenna end we have low impedance high current? Another case when current across the coil CAN be different? Yuri, K3BU.us |
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On 13 Nov 2003 06:02:50 GMT, (Tdonaly) wrote:
For those of us who like to lurk, such discussions can be entertaining, but are essentially worthless, since they usually only consist of pronouncements from on high unaccompanied by anything resembling logic or proof. Some baseless technical rhetoric can be thought-provoking, however, just as some religious beliefs are. Too bad most of it isn't. Hi Tom, Quite true. On the other hand, there is always an element of substance to be investigated, or to reinvigorate long unexercised issues. You said as much, but I don't mind putting some work into these things to test the perspective of their impact. The issue of lumped versus distributed loads has enough of that perspective to merit discussion. It is too bad it is attended with such a circus mentality. Further, it also illustrates how poor planning, testing, and specification can seriously prejudice an outcome. Even if the topics are specious, it can be shown that their conclusive proofs are often spun from sheer imagination or frauds (aka fractal claims). These tests of logic are often more important than the lack of substance (look at all the folderol of photons, tachyons and such metaphysical guff). For instance, it motivated Mark to enquire into how much effect moving the solenoid could have (which my model confirmed in its own tortured way). It has also motivated Yuri to perform measurements with more care to details and greater coverage (not just two data points). Roy emerged to do some bench work (he may yet change his mind, but I suppose that is stretching my luck ;-) All fairly typical behaviors for our supposed avocation; but growing rarer with the haughty attitude that mental gymnastics can answer it all. To this point I've finished viewing one of Robert Pease's Online seminars (Use and Mis-use of Amplifiers) and his single thumped home admonition was to "Eschew SPICE." For those who want the straight skinny from a battle hardened bench designer, I recommend his online work at: http://www.national.com/rap/ on the other hand, for those looking for cut-and-paste greek citations, they will be put against the wall. :-) Where's my bazooka? 73's Richard Clark, KB7QHC |
KB7QHC:
Take the simple question I offered you some time ago: "What is the value of this inductor?" You have never responded to this, nor offered an anticipated value for your own, future work. Value as inductance? Take typical mobile antenna, or from info by W9UCW, resonate it on particular ham band with inserted inductance, calculate the value and you got it. Then check the resonant frequency, if it is not what you are aiming for, readjust the inductance or stinger length. Again, our first to step was to answer the question: is it the same or more like around 50% difference. If we agree that it isn't, then we go and investigate and try to fit the calculations and correlate specific setups. W9UCW took his appart (doen some time ago), I have right now my 72 Buick LeSabre with Hustler masts, coils and some home brewed coils. I can provide dimensions, coil inductances for those who want to calculate Hustlers. Other stuff I have to make, time permitting. Are we merging? Yuri |
Yuri Blanarovich wrote:
Back to the behavior of coils and RF current distribution, isn't the same thing happening in a PI tank of amplifiers? At one end we have hi impedance (tube side) low current, at the antenna end we have low impedance high current? Another case when current across the coil CAN be different? A PI tank is a three or four terminal network so the difference is understandable. The basic problem seems to be in considering the coil in an antenna to be a two terminal lumped component when it really is a 2+ terminal network including attenuated reflections, displacement currents, and multiple paths to ground. -- 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! =----- |
Yuri, K3BU wrote:
"My point is that I argued that current is different, not how precisely I can calculate or offer calculted proof." The 19th edition of the ARRL Antenna Book included a CD-ROM containing a program to optimize whip loading. The book also has a section on loading coil design. Network analysis may be inapplicable, but the simple argument that the current is likely different at the two ends of an antenna loading coil is elegantly made by Fig 6 on page 16-4 of the 19th edition of the ARRL Antenna Book. It shows a simple whip over a ground plane as an equivalent circuit of distributed inductance and capacitance. It`s obvious that capacitance near the feedpoint bleeds current to ground which is thus unavailable at inductance further from the feedpoint. The antenna is, unlike a transmission line, unbalanced. Some energy escapes the confines of the antenna, and isn`t all available from temporary storage to travel on its path along the antenna away from the feedpoint. Decline of current in the loading coil is plotted in the figure. Yuri`s point is proved. Look at Fig 6. The picture is worth a thousand words. Best regards, Richard Harrison, KB5WZI |
Yuri`s point is proved. Look at Fig 6. The picture is worth a thousand words. Best regards, Richard Harrison, KB5WZI Yes, but then on page 16-7 Fig 10 they show that current across the coil is constant, which situation I analyze in my article at www.K3BU.us as an error being perpetuated since 1955 by Belrose. W8JI used this picture to "see, it is constant" :-) I wonder if 20th edition has the same stuff. I haven't got new book yet. Yuri |
Given the length and diameter of the top and bottom antenna sections, and the LENGTH and DIAMETER of the loading coil, program LOADCOIL will calculate coil inductance and the number of turns needed to resonate the antenna to any required 1/4-wave frequency. The program allows the coil to slide up and down the antenna to optimise radiating efficiency versus physical implementation. The inductance value, number of turns and wire gauge are automatically varied to maintain 1/4-wave resonance versus height. As a self-check on resonance and other results, the base feedpoint Zin is calculated. Zin can be used in another program to calculate tuner L and C settings. A base loading coil can be conveniently included in a tuner. The distribution of current along the antenna, including along the coil especially if it is a long helix, and phase relationships, are necessarily taken into account to estimate loss and radiation resistances. But such data is not outputted because it's of no practical use to anybody and not worth the screen space. The simple radiation pattern of short vertical antennas is already very well known. Download program LOADCOIL in a few seconds from website below and run immediately. ---- ======================= Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.g4fgq.com ======================= |
Yuri, K3BU wrote:
"W8JI used this picture (Fig 10) to "see, it is constant". But that was only by specification. It`s the same as saying, "Let`s say the line is lossless". The text reads: "The loading coil acts as the lumped constant that it is, and disregarding losses and coil radiation, maintains the same current flow throughout." This says that in the impossible case of zero radiation and zero loss, the coil current is the same at both ends of the coil. This is close enough for a coil at 50 Hz, but unlikely at 5 MHz. A real loading coil such as a bug catcher, has a real length. The combination of incident and reflected waves at each point along the length of the antenna produces a different voltage, just as seen in a transmission line. This effect prevails in an antenna, too. Just as on a transmission line, the voltage variation represents an impedance variation. Impedance is high at the open-circuit end of the antenna , and it it is low 90-degrees back from that open circuit. Since some length is filled with the coil, there is a difference in volts at the ends of the coil due to the standing wave on the antenna. The feed paths to the coil are unbalanced as shown in Fig 6. That is not shown in Fig 10 which is meant to show the difference in antenna current above and below the coil, not what happens in the coil itself. The authors specify an idealized coil which has the same current in and out. This is only a declaration, not a real world situation. Best regards, Richard Harrison, KB5WZI |
Richard Harrison wrote:
This says that in the impossible case of zero radiation and zero loss, the coil current is the same at both ends of the coil. This would be true for traveling-wave antennas. But in a standing-wave antenna, the net current is the sum of the forward current and the reflected current. Even if the coil had zero radiation and zero loss, a real-world coil would have a delay through the coil. That delay changes the relative phase between the forward and reflected currents making the net current different at each end of the coil even for a coil with zero radiation and zero loss. The forward currents would be equal into and out of the coil. The reflected currents would be equal into and out of the coil. But their phasor sum would differ due to phasing. Assume the forward current and reflected current are in phase at zero degrees at the feedpoint. The net current is simply the algebraic sum of those two values. But 45 degrees out from the feedpoint, the forward current is at 45 degrees and less than at the feedpoint. The reflected current is at -45 degrees and greater than at the feedpoint and the sum of the two currents is the sum of two phasor currents 90 degrees apart. At 90 degrees, at the end of the antenna, the forward current and reflected current are equal and phasor sum to zero. -- 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! =----- |
On Thu, 13 Nov 2003 06:57:17 GMT, Richard Clark
wrote: [interesting comments snipped] | |All fairly typical behaviors for our supposed avocation; but growing |rarer with the haughty attitude that mental gymnastics can answer it |all. To this point I've finished viewing one of Robert Pease's Online |seminars (Use and Mis-use of Amplifiers) and his single thumped home |admonition was to "Eschew SPICE." | |For those who want the straight skinny from a battle hardened bench |designer, I recommend his online work at: |http://www.national.com/rap/ |on the other hand, for those looking for cut-and-paste greek |citations, they will be put against the wall. :-) No, they'll just swithch to the Taguchi method. |
Richard,
You have written quite extensively on this thread, a lot of it being comments that I just dont understand. If you don't like the way it is going or the people involved are not coming to you' as is their job, to present absolute proof then why bother with these people or the thread. Since you and Tom are like minded establish a thread that you can banter back and forth without interuption from the roudies. Tom mentioned somebody else so you may have a quarum to go your own way, which would be a pity Can't you bend just a bit and go with the flow when unsurmountable proof is not presented to you first, which you say is everybodies job. Looking at the posters that are already involved with this thread including those who have now decided to abstain it would appear that there is some interest in the subject. Didn't you yourself invite me to participate ? If so you must certainly had some interest in what the lesser people were saying. Why not look at the possitives presented and put aside attempts to deflate or deride honest attempts to explain. You are apparently a computor expert so why not derive a system where a inductance is transfered to a system that can easily be modeled since there seems to be some interest in the matter and you would good chance of becoming a hero to all. Still your friend and hanging on Art (Tdonaly) wrote in message ... Richard wrote, On 13 Nov 2003 04:21:58 GMT, oSaddam (Yuri Blanarovich) wrote: I want to see how well can we track modeling, and what is the proper way to model the inductors and "force" the Eznec et al to tell the truth? Hi Yuri, This is the problem of framing the question. The choice of a lumped component in EZNEC (as I understand it) is entirely your choice, just as is the choice in the number of radials to put under an antenna. If the lumped component is inappropriate (just as would be a non representative ground system or incorrect choice of ground models) that is the consequence of your bad choice. Your page already offers the solution for a solenoid, a simple protocol that fits the situation you presented and to which you identified and presented Tom as performing inappropriately. In other words, he did not practice the protocol, and so it seems, neither have you. This returns us to the adequacy of actually framing the specification (instead of the question). Can you present a format for testing BOTH the physical model and the software model that allows the software model to be accurate? To this point, no. Not knowing the particulars that lead to the data offered, and then comparing to a poor model was in fact no proof at all. That data, and even my model barely reconcile to any of but one possible fact: a current differential across a long solenoid (something that Roy has not dismissed even if that answer has been projected upon him by theory spinners). It conforms to your thesis, but it hardly proves it (simply because it inverts your expectations shown in this so-called data). Take the simple question I offered you some time ago: "What is the value of this inductor?" You have never responded to this, nor offered an anticipated value for your own, future work. You condemned Tom for his poor work, and yet he is the only one to offer a working value; and if the lack of resonance in my model is any indication, it is an entirely wrong value, but to this point it is the ONLY specific value offered by ANYONE. What value is this data, your proof, if you cannot provide such a fundamental characteristic? OK, so you are going to abandon it as anecdotal and replace it with your own effort. Do you have an estimated value for such fundamental issues as the size of the radiator, the solenoid, its value, its placement, the ground system? It took me less effort to spin up a model than write this missive. What overwhelming problems do you dwell on such that this discussion goes mute? I am puzzled how you can demand that others perform the benchwork when you cannot present the problem for them to examine. Roy opened a new thread doing just that, and the sneer review pointed out it was not the same (as what?). Of course it wasn't, no one has any but the barest of details. His inductor was too small and in the wrong place to accept as a valid representation of the issue goes the rebuttal; but it proved you right by conforming to all the particulars. Now if that doesn't hold the record for self-contradiction, I am sure it will be eclipsed tomorrow. That was an exercise in framing the answer, a practice of the cut-and-paste theorists that speed read through their bibles looking for a passage in greek that corresponds to their view of the world. When these threads turn to examining "the truth," it is more than obvious that such a pursuit is bogged down from the beginning and not necessarily due to an artifact of any tool as it is of the mind. 73's Richard Clark, KB7QHC Hi Richard, it's obvious that the purpose of these discussions among the pathologically competitive is not to reveal truth, but to enhance the reputation for infallibility of the professional egos involved. (I'm not writing of you, Roy, or Keith.) For those of us who like to lurk, such discussions can be entertaining, but are essentially worthless, since they usually only consist of pronouncements from on high unaccompanied by anything resembling logic or proof. Some baseless technical rhetoric can be thought-provoking, however, just as some religious beliefs are. Too bad most of it isn't. 73, Tom Donaly, KA6RUH |
Cecil Moore wrote: Jim Kelley wrote: I'd like to hear an explanation for ANY current difference across a coil that is supposedly behaving as a lumped inductor. But the test really should be for the same type of antenna used in Yuri's discussion; Jim, did you fail to notice that arc-cos(0.95) = 18.2 degrees? No. But I have failed to notice any explanation for it other than you and Yuri have provided. 73, Jim AC6XG |
Cecil Moore wrote in message ...
Mark Keith wrote: More thoughts from the rubber room...Lets say you, Yuri and crew are correct and the current taper is large across the coil. Lets say the coil is still a 1 ft long bugcatcher coil. Lets say the current is fairly constant below the coil. What will the real world effect be of this phenomenon? Roy's measurements vindicated Yuri's prediction. Current in equals 1.0 amp at zero degrees. Measured current out equals 0.95 amps. arc-cos(0.95) = 18 degrees. Yuri's prediction was right on. What else is there to argue about? Even the small toroidal coil functioned exactly as predicted by Yuri. My argument boils down to: What does this mean to the antenna builder or modeler? If any discrepancy is so small to be barely measurable, all this speculation about gross error when modeling is *to me* a load of hooey. Even if the current varies, which BTW, I never claimed would be exactly perfect front to back, it should have so little effect on accuracy to be a non issue. Where is the beef that this claimed variation of current across a coil causes drastic modeling or coil placement calculation errors? Sorry, I just don't see it. What am I missing here? MK |
Mark Keith wrote:
My argument boils down to: What does this mean to the antenna builder or modeler? To the antenna user, or the antenna builder/modeler who doesn't care about current distribution, it would probably mean nothing. If any discrepancy is so small to be barely measurable, all this speculation about gross error when modeling is *to me* a load of hooey. The discrepancy varies anywhere from barely measureable to very measureable. Where is the beef that this claimed variation of current across a coil causes drastic modeling or coil placement calculation errors? Sorry, I just don't see it. What am I missing here? MK I think it should only matter to people who want to give advice on the subject. 73, Jim AC6XG |
Mark, I have often wondered about the meaning of the American word "hooey".
Following a few speed-reads of this disgraceful, un-ending thread, in conjunction with your description, I now have a better understanding. Thank you. Who says the Internet is not educational? --- Reg. |
Jim Kelley wrote:
Cecil Moore wrote: Jim, did you fail to notice that arc-cos(0.95) = 18.2 degrees? No. But I have failed to notice any explanation for it other than you and Yuri have provided. Assuming the forward current and reflected current are in phase at the feedpoint, the 5% reduction in net current at the other end of the coil appears to be because the forward current and reflected current are not in zero phase at that point. The phase of the forward and reflected currents are changing in a predictable manner but the phase of their sum, the net current, doesn't change much if they are in the ballpark of the same magnitudes. I think Roy measured that net current phase. -- 73, Cecil, W5DXP |
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