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3 antennas modeled with EZNEC
Thanks to Wes, n7ws, I found out how easy it is to model a helical coil
with EZNEC. The following three antennas were modeled using the same coil, 4.5 turns, 12 inch diameter, 10.8 inches long, using approximately 14 feet of wire. The antennas are similar. The frequencies are different to illustrate three different arguments. EZNEC zero-impedance loads were placed directly below and directly above the coil to ascertain the currents. The accompanying .ez files can be downloaded and run on EZNEC if desired. 1. The first antenna is a simple center-loaded 1/4WL monopole. The lengths of wire above and below the coil are approximately the same as the length of wire used in the coil. This one illustrates the current taper through the loading coil. Calculations indicate that the coil occupies approximately 20% of the electrical length of the antenna. http://www.qsl.net/w5dxp/octcoil1.gif http://www.qsl.net/w5dxp/octcoil1.ez 2. The second antenna is electrically 3/4 wavelength long. This one illustrates how the current at the top of the loading coil can be greater than the current at the bottom of the loading coil. http://www.qsl.net/w5dxp/octcoil2.gif http://www.qsl.net/w5dxp/octcoil2.ez 3. The third antenna illustrates the phase-reversing coil described by Kraus in _Antennas_For_All_Applications_, 3rd edition. It is similar in concept to the Diamond NR72B when used on 70 cm. The current at the bottom of the coil is 180 degrees different in phase from the current at the top of the coil which means - for 1/2 of the RF cycle, current is flowing into both ends of the coil at the same time. For the other 1/2 cycle, current is flowing out of both ends of the coil at the same time. http://www.qsl.net/w5dxp/octcoil3.gif http://www.qsl.net/w5dxp/octcoil3.ez It appears to me that EZNEC handles the segmented wire coils in a manner related to the real world. -- 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! =----- |
Welcome back from the dark side Cecil...
"Cecil Moore" wrote in message ... Thanks to Wes, n7ws, I found out how easy it is to model a helical coil ! =----- |
It appears to me that EZNEC handles the segmented wire coils in a manner related to the real world. -- 73, Cecil http://www.qsl.net/w5dxp Eggscellent!!! Thanks for putting up with the flat earth society. Yuri, C6AYB |
Cecil wrote,
Thanks to Wes, n7ws, I found out how easy it is to model a helical coil with EZNEC. The following three antennas were modeled using the same coil, 4.5 turns, 12 inch diameter, 10.8 inches long, using approximately 14 feet of wire. The antennas are similar. The frequencies are different to illustrate three different arguments. EZNEC zero-impedance loads were placed directly below and directly above the coil to ascertain the currents. The accompanying .ez files can be downloaded and run on EZNEC if desired. It certainly is interesting how a person who, only a short time ago was railing against "the math model," suddenly gets religion when he thinks it agrees with him. EZNEC not only uses math to reach its conclusions, that's *all* it uses, plus a few assumptions about how current is distributed over antenna segments. Glad you've joined the fold, brother Moore. 73, Tom Donaly, KA6RUH |
Tdonaly wrote:
Cecil wrote, Thanks to Wes, n7ws, I found out how easy it is to model a helical coil with EZNEC. The following three antennas were modeled using the same coil, 4.5 turns, 12 inch diameter, 10.8 inches long, using approximately 14 feet of wire. The antennas are similar. The frequencies are different to illustrate three different arguments. EZNEC zero-impedance loads were placed directly below and directly above the coil to ascertain the currents. The accompanying .ez files can be downloaded and run on EZNEC if desired. It certainly is interesting how a person who, only a short time ago was railing against "the math model," suddenly gets religion when he thinks it agrees with him. It is certainly interesting that you choose to mount an ad hominem attack instead of providing an iota of technical content. I do not rail against all math models, just the ones that don't match reality. I require my math models to give the correct answer. Others obviously have lower standards for math models than I do. One rock plus one rock equals two rocks is a math model with which I fully agree. Coils with zero capacitance is a math model with which I disagree. Now please tell us why lumped inductive reactances don't agree with wire segment coils, stubs, or reality. -- 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 Fri, 06 Feb 2004 06:12:43 -0600, Cecil Moore
wrote: Now please tell us why lumped inductive reactances don't agree with wire segment coils, stubs, or reality. Operator error. It's like trying to measure Ohms without turning on the meter's current source. There's a lot of institutionalized ignorance in these threads. |
Richard Clark wrote:
wrote: Now please tell us why lumped inductive reactances don't agree with wire segment coils, stubs, or reality. Operator error. Yep, the error is in the operator's choice of a model that doesn't match reality. -- 73, Cecil, W5DXP |
On Fri, 06 Feb 2004 13:32:40 -0600, Cecil Moore
wrote: Yep, the error is in the operator's choice of a model that doesn't match reality. Institutionalized here for the sake of argument. |
Cecil wrote,
(snip) I do not rail against all math models, just the ones that don't match reality. I require my math models to give the correct answer. (snip) That's code. It means "I do not rail against all math models, just the ones that don't agree with me. I require my math models to give the answer I've already made up in my head." 73, Tom Donaly, KA6RUH |
Cecil Moore wrote in message
2. The second antenna is electrically 3/4 wavelength long. This one illustrates how the current at the top of the loading coil can be greater than the current at the bottom of the loading coil. http://www.qsl.net/w5dxp/octcoil2.gif http://www.qsl.net/w5dxp/octcoil2.ez Why the 3/4 wave example? This is NOT what I had in mind. What I would like to see, is you take a 8 ft mobile whip for 80m. Start with a center load. Note the current taper. Then place the coil below the midpoint level. Note the current taper. Then place the coil above the midpoint level. Note the current taper. You should be able to find a configuration that provides max current at the top of the coil, if what you claim is true. I want to see max current at the top of the coil in the SHORT loaded 8ft mobile whip for 80m. Not a funky overly tall 3/4 wave antenna. I'd try it myself, but I only have the demo of eznec and don't have the segment capability. Then if you can see this happen in the model, I'd like to see it confirmed in the real world. If this occurs, then I might start to think what you claim holds some water. I'll reserve further comment until you can try this simple test. MK |
Cecil Moore wrote in message
2. The second antenna is electrically 3/4 wavelength long. This one illustrates how the current at the top of the loading coil can be greater than the current at the bottom of the loading coil. http://www.qsl.net/w5dxp/octcoil2.gif http://www.qsl.net/w5dxp/octcoil2.ez Why the 3/4 wave example? This is NOT what I had in mind. What I would like to see, is you take a 8 ft mobile whip for 80m. Start with a center load. Note the current taper. Then place the coil below the midpoint level. Note the current taper. Then place the coil above the midpoint level. Note the current taper. You should be able to find a configuration that provides max current at the top of the coil, if what you claim is true. I want to see max current at the top of the coil in the SHORT loaded 8ft mobile whip for 80m. Not a funky overly tall 3/4 wave antenna. I'd try it myself, but I only have the demo of eznec and don't have the segment capability. Then if you can see this happen in the model, I'd like to see it confirmed in the real world. If this occurs, then I might start to think what you claim holds some water. I'll reserve further comment until you can try this simple test. MK |
Tdonaly wrote:
That's code. It means "I do not rail against all math models, just the ones that don't agree with me. I require my math models to give the answer I've already made up in my head." No, I require a math model of a coil that agrees with Roy's and Tom's measurements. A lumped inductive reactance doesn't do that. My math models are dictated by reality. Therefore, I live in the real world and you live in a world created and dictated by your math models. I prefer my world. You obviously prefer yours. -- 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:
Why the 3/4 wave example? In order to illustrate higher current at the top of the coil than at the bottom, of course. You should be able to find a configuration that provides max current at the top of the coil, if what you claim is true. I just did in the 3/4WL example. One cannot get higher current at the top of the coil in a 1/4WL electrically long antenna. For a 1/4WL antenna, the maximum current is at the feedpoint and tapers down to the tip. I want to see max current at the top of the coil in the SHORT loaded 8ft mobile whip for 80m. Well, good luck on that one. I think it's impossible. Blood out of a turnip comes to mind. If you think I ever said or implied that I could do that, you are as mistaken as you can possibly be. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Cecil Moore wrote:
Mark Keith wrote: Why the 3/4 wave example? In order to illustrate higher current at the top of the coil than at the bottom, of course. You should be able to find a configuration that provides max current at the top of the coil, if what you claim is true. I just did in the 3/4WL example. One cannot get higher current at the top of the coil in a 1/4WL electrically long antenna. For a 1/4WL antenna, the maximum current is at the feedpoint and tapers down to the tip. uh huh..... I want to see max current at the top of the coil in the SHORT loaded 8ft mobile whip for 80m. Well, good luck on that one. I think it's impossible. Blood out of a turnip comes to mind. If you think I ever said or implied that I could do that, you are as mistaken as you can possibly be. What has all this been about? Bugcatchers and other short loaded mobile antennas. All shorter than 1/4 wave. Good grief....I rest my case. My theory? I still think the current across the coil is *fairly* constant. I'm *still* of the opinion that the *apparent* radical taper across the coil is more due to the presence of the capacitance above the coil. I think Roy described this in more accurate terms, but I have to reread the thread. I'm *still* of the opinion that if you could measure the current INSIDE the windings of the coil, a couple or three turns in from each end, you would not see near the difference you all do. I do think it's quite normal to have a slight taper, as you would with any other radiator that is shorter than 1/4 wave. So what? But these are just my gut instincts using my built in BS filter. I'm absolutely certain than any error in modeling a short mobile antenna using lumped coils is not worth worrying about. This was the main gist of the argument by Yuri. It was the bottom line. He claimed we were modeling in fairly gross error due to this new found revelation of coil current taper. He promised a new revelation in coil positioning that would turn the mobile antenna world on it's head. Or at least the hype seemed to imply this. But I'm afraid many beat him to it years ago. As far as phasing coils, yep, you might have an issue there. But it appears you may have been enlightened to a workaround even in that case. Isn't life grand? MK -- http://web.wt.net/~nm5k |
On Fri, 06 Feb 2004 18:33:24 -0600, Mark Keith wrote:
I'm absolutely certain than any error in modeling a short mobile antenna using lumped coils is not worth worrying about. That has been shown several times - unless your skin crawls with differences of 0.5dB This was the main gist of the argument by Yuri. It was the bottom line. He claimed we were modeling in fairly gross error due to this new found revelation of coil current taper. And that pilot's error was addressed before the soap opera began. He promised a new revelation in coil positioning that would turn the mobile antenna world on it's head. Umm yes. The excuse is snow, but given the tapering heat wave reports, the coils should clear that away in half an hour. Patents pending!!! - any further discussion constitutes a violation of Intellectual Property rights subject to suit (40R w/2 pair of pants). 73's Richard Clark, KB7QHC |
Mark Keith wrote:
I'm *still* of the opinion that if you could measure the current INSIDE the windings of the coil, a couple or three turns in from each end, you would not see near the difference you all do. Wes's and my modeling show a smooth current taper through the coil. Here's the taper predicted by EZNEC through the coil for octcoil1.ez http://www.qsl.net/w5dxp/taper1.gif I do think it's quite normal to have a slight taper, .... Then you disagree with the guys who say it has no taper. Guess what, Mark? That puts you on my and Yuri's side of the argument. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Cecil wrote,
Mark Keith wrote: I'm *still* of the opinion that if you could measure the current INSIDE the windings of the coil, a couple or three turns in from each end, you would not see near the difference you all do. Wes's and my modeling show a smooth current taper through the coil. Here's the taper predicted by EZNEC through the coil for octcoil1.ez http://www.qsl.net/w5dxp/taper1.gif I do think it's quite normal to have a slight taper, .... Then you disagree with the guys who say it has no taper. Guess what, Mark? That puts you on my and Yuri's side of the argument. -- 73, Cecil http://www.qsl.net/w5dxp This is an order of magnitude error. In the thirteenth century, the scholastics would tell their pupils that, since the earth is a ball, if you build two buildings side by side and use a plumb line to build each one, the buildings will be farther apart at the top than at the bottom. Also, if you have a swimming pool with a perfectly flat bottom, the center will be deeper than the sides because it's closer to the center of the earth. No normal people paid any attention to these fellows. The scholastics never specified what things meant in terms of real numbers. Cecil says there's a taper but he doesn't attempt to say how much. Yuri thinks it's a lot. Cecil seems to agree with him, but neither fellow has been willing to back his theory with a $$$$ NEW $$$ [{### IMPROVED ###}] mobile antenna. I think any rational observer would have to conclude that if Yuri and Cecil are right, they're only right in the 13th cent. scholastic sense, and that their whole argument doesn't amount to a hill of beans. 73, Tom Donaly, KA6RUH |
Tom Donaly, KA6RUH:
The scholastics never specified what things meant in terms of real numbers. Cecil says there's a taper but he doesn't attempt to say how much. Yuri thinks it's a lot. Cecil seems to agree with him, but neither fellow has been willing to back his theory with a $$$$ NEW $$$ [{### IMPROVED ###}] mobile antenna. Go to www.K3BU.us and look at the article, measurements and pictures. http://www.k3bu.us/loadingcoils.htm Cecil explained what's happening, shined some light on it and the work is in progress to enlighten the flat earth society. It is not "our theory", it is reality that was described before us by Kraus, ON4UN and others. I used the knowledge to design more efficient mobile antenna for 160. If you understand the current distribution along the loaded antenna, then you can maximize it for better efficiency (roughly proportional to the area under the current curve). Stand by. Yuri, K3BU.us |
Yuri Blanarovich wrote:
It is not "our theory", it is reality that was described before us by Kraus, ON4UN and others. And demonstrated through actual measurements made by W7EL and W8JI. It's hard to believe anyone rejects those measurements. -- 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 Clark wrote:
So, what gets responded to, the efficiency or Cecil's goofball claims? Install a one ohm resistor at a current loop. Observe the voltage across it as a sine wave. Are you saying that the voltage across that one ohm resistor is not proportional to the current in magnitude with the same phase? The current is positive for 1/2 cycle and negative for 1/2 cycle. The sign denotes the direction of current travel in the wire. Have you used the DC model on AC circuits for so long that you have forgotten that AC current reverses direction every 1/2 cycle? -- 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 Fri, 06 Feb 2004 22:18:26 -0600, Cecil Moore
wrote: Richard Clark wrote: So, what gets responded to, the efficiency or Cecil's goofball claims? Classic example: Install a one ohm resistor at a current loop. |
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Cecil Moore wrote in message
I do think it's quite normal to have a slight taper, .... Then you disagree with the guys who say it has no taper. Guess what, Mark? That puts you on my and Yuri's side of the argument. Maybe so, but I place much less importance on this than he does. To me, it means very little, if anything. It surely will not effect how I will design mobile antennas. After all, as Wes pointed out on his web page, the change in radiation resistance is what really improves the efficiency of a short loaded antenna. Not the current distribution in itself. The improved current distibution is just a method used to change the radiation resistance. Taper or no taper, in the usually short 1 ft or so space a coil would occupy, "1/8 the length of a 8 ft whip" the difference either way is not worth worrying about. And the worrysome taper is only in the upper section of the coil, so really it's less than 1/8 of the total antenna length. Most of the plots I see are more bow shaped than a gradual taper due to the peak in current. I'm glad Wes commented on the current peak...This was something I had seen previously in modeling the antennas/coils a few weeks ago, and had wondered about.. If we could do away with the high ground losses, we wouldn't need to elevate the coils, or use hats. That's why often a base load 10-11m vertical on a large car roof is about as good as a center load. Less ground loss due to the better psuedo ground plane under the antenna. MK |
Richard Clark wrote:
On Fri, 06 Feb 2004 22:18:26 -0600, Cecil Moore wrote: Richard Clark wrote: So, what gets responded to, the efficiency or Cecil's goofball claims? Classic example: Install a one ohm resistor at a current loop. In many circuits, a one ohm resistor is a negligible amount of resistance and allows one to view the current waveform on an o'scope. If you like, use a toroidal pickup coil to view the current waveform. The current waveform will look the same either way. -- 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:
Cecil Moore wrote in message Then you disagree with the guys who say it has no taper. Guess what, Mark? That puts you on my and Yuri's side of the argument. Maybe so, but I place much less importance on this than he does. You may also place less importance on strawberry ice cream than he does. To me, it means very little, if anything. Yuri was accused of "Repeating misleading information". Here is a typical response to one of Yuri's postings: "You like to call names, insult people, and argue rather than take the time to learn basic electronics. ... If you look at HOW an inductor works, the current flowing in one terminal ALWAYS equals the current flowing out the other terminal." Note the word "ALWAYS". The ad hominem attacks upon Yuri is probably one reason he considers the subject to be important. Someone probably rejected relativity and said, "How much effect does the orbit of Mercury have on the people of earth?" -- 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 Sat, 07 Feb 2004 09:46:57 -0600, Cecil Moore
wrote: Richard Clark wrote: On Fri, 06 Feb 2004 22:18:26 -0600, Cecil Moore wrote: Richard Clark wrote: So, what gets responded to, the efficiency or Cecil's goofball claims? Classic example: Install a one ohm resistor at a current loop. Another Classic goofball example: In many circuits |
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K3BU:
[snip] | |I used the knowledge to design more efficient mobile antenna for 160. KB7QHC: What design did you start with and at what efficiency? What design did you end up with and at what efficiency? What was the improvement in efficiency? N7WS: So now it's 0.51% efficient instead of only 0.49% right? [g] Nope, more like going from not getting answers to my calls or CQ (S0 or less :-) to getting reports from W6, through P4 to Eu of S6 to S9. Even getting hell from W8JI for wiping out - QRMing the DX window. You learned heads figure out the efficiency improvement in dBm, uV or dB or S units. It may not jive with your decimal points, but is OK with me. In the past Cecil showed some results from mobile antenna shootouts, where simple change in position of the loading coil can mean dBs or tens of dBs difference. Might not be reflected in your modeling results, but reality speaks. Those who built and used the stuff know it. Those who calculate it "know better"? This is getting amusing and eye opening how many flat earth society members are out there. Keep on harping! KB7QHC: Marketing claims are cheap and I need only pick up a copy of People Magazine off the newsstand to read them for free. I am not marketing nothing (yet), just defending the truth and reality. YMMV Yuri, K3BU |
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The long and short of it is that you have absolutely nothing to back up your assertions of vastly improved efficiency - that's the reality compared to your testimonials that wouldn't get a vote on American Idol. 73's Richard Clark, KB7QHC You are right, and you uncovered me. Shocks! Yep, the real life results mean nothing! Long live flat earth! Bring your mobile 160m setup to shootout with mine and let's see your .01 dB difference. Can we stick to arguments without ridicule? Or is W8JI disease spreading around? I am grateful for the "wisdom" displayed here, for it illustrates the level of knowledge and experience. I will use it in my article for the benefit of those who will appreciate it. Some of the jabs will end up looking silly. Again, Cecil, my hat off to you for your help and patience. Yuri da BUm |
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What are the answers to the technical questions: What design did you start with and at what efficiency? Classical mobile whip with 160m loading coil and whip. What design did you end up with and at what efficiency? Improved K3BU design based on knowledge gained from current distribution in a loading coils. Details can be obtained against non-disclosure agreement. What was the improvement in efficiency? Significant, from S0 to S7 - S9. 73's Richard Clark, KB7QHC 73 Yuri, K3BU/m |
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Richard Clark wrote:
I offered an EZNEC analysis that supported (circumspectly) Yuri's position, but he blew it off chasing rainbows. Don't know about anybody else, but that posting never appeared on my news-server. That's the first time I have ever seen it. -- 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! =----- |
Richard Clark wrote:
The long and short of it is that you have absolutely nothing to back up your assertions of vastly improved efficiency ... Even it that were true, it wouldn't change the result of the argument based on W8JI's assertion: If you look at HOW an inductor works, the current flowing in one terminal ALWAYS equals the current flowing out the other terminal. The only question is: Do you support W8JI's position even though his own measurements proved otherwise? -- 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 Sat, 07 Feb 2004 17:30:06 -0600, Cecil Moore
wrote: I offered an EZNEC analysis that supported (circumspectly) Yuri's position, but he blew it off chasing rainbows. Don't know about anybody else, but that posting never appeared on my news-server. That's the first time I have ever seen it. You mean you actually read this group? |
On Sat, 07 Feb 2004 17:38:53 -0600, Cecil Moore
wrote: Richard Clark wrote: The long and short of it is that you have absolutely nothing to back up your assertions of vastly improved efficiency ... Even it that were true Even IF |
Richard Clark wrote:
wrote: Richard Clark wrote: The long and short of it is that you have absolutely nothing to back up your assertions of vastly improved efficiency ... Even it that were true Even IF Shirley, you understand a conditional statement, Richard. The following is a logically true statement: "If the moon was made of green cheese, then a cow could indeed jump over it." May I recommend a good logic textbook? _Logic_, by Ruby. -- 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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