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Yes but I believe that the early computorisationd he used was based first on
mechenical designed elements which were then imputted.He did not mess with the element diameters after that.As an aside if you densly populated a boom with elements many are put off by the low impedance being totaslly unaware that an additional reflector an up the input impedance back again...... another example of what coupling can do for antennas Art "Yuri Blanarovich" wrote in message ... Another was from the Central States VHF Society and gives results of their 2004 gain comparisons of many different antennas. Gain of these versus boom length looks very ragged. Best regards, Richard Harrison, KB5WZI Gain vs. boom length makes sense only when comparing or tracking the same antenna design i.e. Yagi with multiple elements. One can design lousy antenna on a long boom. Jim Lawson, W2PV was one who after some modeling showed that gain in the properly designed antenna is roughly proportional to the boom length rather than to number of elements. Some manufacturers "beefed up" their antennas by sticking more elements on the same boom claiming better performance. Yuri, K3BU.us |
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Tom, let me be direct without being disrespectful What I modelled was a boom
length of 7ft for 20 metres and it is an abnormal yagi design which does not fit what you are offering. I do not believe that NEC programs vary too much on standard forms but when using tightly clustered elements on a short boom lots of other things come in to play, and one has to be sure that the program is all encompassing as designed to handle ALL abnormalities. Obviously what you have offerred has serious problems on short yagi's let alone abnormal design yagi's. It is my belief that because an element reradiates a portion of the RF that it received, extra elements that are closely clustered can provide increased gain. Yes. my model confirmed that but I was hoping that experts could point to a mathematical analysis of max gain per unit length that was exacting in gain provided and not "close enough" and not marred by other things that can occur by measuring in the field. It would appear from the responses that efforts in this area has not been undertaken and which I will have to live with that. But I do thank you for your offering Art "Tom Ring" wrote in message . .. wrote: Tom, where is the link that goes with this info? It doesn't mean anything as it stands Art What? Of course it means something. It's an equation along with the constraints. Run any current decent 1 wavelength, or longer, yagi in your favorite modeling program, and it will tell you whether you are near the gain you should get for a well behaved yagi. Or it might tell you the model isn't very accurate. It works well to test known designs against unknown quality programs without having the known good modeling program or test range. If you want the database it was derived from, that might be arranged, but it is in from a database program that Microsoft Office won't read, so you might be out of luck there. tom K0TAR |
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No appreciable difference between them and NEC program results. You can build every bit as good of an antenna using the curves and given formula as you can a NEC program. Optimization of antenna built from either data still requires the same cut and try tweaking to get the last .001 db out. For all practical purposes the ARRL curves are as good as any. Obviously you have some impractical uses in mind. " wrote in message news:gDfdd.278515$D%.137716@attbi_s51... "Jimmie" wrote in message . com... A graph from NEC data is going to be pretty much like a graph from the ARRL books. Come on Jimmy,' pretty much like' doesn't cut it on this newsgroup or in any of the professions The same as pretty close is not accepted when doing math at college. The curves in the ARRL book were done on 'standard' yagis measured in the field, at least two of the curves therefore have measuring errors, and possibly three of those do not match NEC formulated curves. Since you do not want to reinvent the wheel which curve or formula do YOU want all to follow for short boom antennas i.e. which curve, and there are many, represents the "wheel" . that can be specifically used as the datum curve in response to my specific request? Note, a NEC produced gragh will produce a scattering of points for different yagi's but only ONE point for MAX GAIN PER UNIT LENGTH OF BOOM regardless of how many elements are used which when used on short booms produce coupling effects which change current flow, an effect not generally seen when elements are not critically coupled as in the standard yagi.. Thus the reason I was specific in my request which should have removed comments such as 'Patents" from those who seek arguments . Art By putting the data in a graphic form your are placing the same limits on the data as they had to in the ARRL books. The ARRL graphs give you a pretty good idea of what goes on when you change element spacing, number of elements and so on. What they dont do is alllow you to perform optimization like the NEC programs . Graphing a NEC program output would be the same as going back to the time all you had was the graphs to go by unless you are willing to do all the calculations on your slide rule or calculator. What I am saying is that you already have this data. No point in reinventing the wheel.Unless you think yiou can get a patent on it Geez Jimmy you are just not reading posts of others ! If you have the requested data then point to a link, if I had the data already I wouldn't ask for help seeking it,. Art " wrote in message news:65Zcd.150611$He1.116446@attbi_s01... Jimmy, I did not want to choose a curve that matches my modelling which you can when presented with three different curves all of which are formulated at different times by different people. I would have thought that the advent of NEC would render these curves redundant ! Art "Jimmie" wrote in message . com... " wrote in message news:xOzcd.263953$D%.243703@attbi_s51... My ARRL books go back a decade or more and the graph showing gain per boom length has several curves based on different measurements e.t.c. Has a graph been made based solely on NEC program findings over say a perfect ground and at a uniform height? Art They probably have been done but there will not be much difference between them and the ARRL graphs. Its been long known how to calculate antenna gain, computers just take the teadous labor out of it. |
" wrote in message news:wAYdd.406148$mD.70164@attbi_s02... Tom, where is the link that goes with this info? It doesn't mean anything as it stands Art wrote in message . .. wrote: My ARRL books go back a decade or more and the graph showing gain per boom length has several curves based on different measurements e.t.c. Has a graph been made based solely on NEC program findings over say a perfect ground and at a uniform height? Art For VHF/UHF yagis in free space - WA2PHW Gain Figure of Merit G = 10 log (5.4075 B + 4.25) for B GT 1 Where G is gain in dBd and B is boomlength in wavelengths. This is from a database of over 100 VHF/UHF yagis compiled in the early 90's. These are all real buildable yagis, and the antenna range numbers closely agree with the computer models. The numbers were heavily influenced by the 10 to 40 element K1FO series. Thanks again Steve. Note that this predicts a zero length yagi should have about 6 dBd gain. Any ideas on why it intercepts there? tom K0TAR |
wrote in message news:tEUdd.167111$He1.55962@attbi_s01... "Chuck" wrote in message news:fVSdd.9064$6P5.7971@okepread02... wrote in message news:bMDdd.293802$3l3.275124@attbi_s03... "Chuck" wrote in message news:XrBdd.8254$6P5.7645@okepread02... snip. ... Hi Art, Ok, I'm always open minded to learn something new... Wow,,,...... there are not many people around who could say that !. Since 99.999% of things presented as new are incorrect most experts have determined that the odds favor them if they label EVERYTHING new as in error. If something comes along that is really new they always have the comment ' I knew about that a long while ago" to fall back on. Hi Art, Anyone who believes they know it all, has much to learn :-) ... The program shows that the normal 2 element is not the optimum in that a polygon of vectors beats a triangle of vectors. At the same time with added elements you get diminishing returns in std and conventional forms. The program showed that 1 to 1.5 dbi was available over the standard 2 element on the same length boom.if one could overcome mechanical restraints. (I was comparing to a Beasely example of what gain could be attained for two elements on a 7 foot boom) Now that is not the end of the experiment as I cannot verify the accuracy of the program, because I did not write it, and I certainly cannot say that my modelling aproach is without error since that is what many 'experts' point to if they don't like the results. It was for that reason I asked if any similar data had been made available for boom length by reputable programmers and antenna 'experts' for comparison purposes ., If these initial results were quoted as accurrate there would be howls from all the resident antenna ' experts" and I would immediately be placed in the six foot hole that they have been trying to put you in for the last eight years Art I get the impression that what you are doing is placing any number of elements on a .1 lambda boomlength, in order to determine if the close proximity EM interactions produce more gain than just the standard 2 elements would on that same boomlength. In the optimization process, some of the resulting element diameters are quite small. You're asking if anyone else has looked into this, and if any results have been published. Is this a correct assessment so far? 73 de Chuck, WA7RAI |
YES
Art "Chuck" wrote in message news:N3ded.9115$6P5.8189@okepread02... wrote in message news:tEUdd.167111$He1.55962@attbi_s01... "Chuck" wrote in message news:fVSdd.9064$6P5.7971@okepread02... wrote in message news:bMDdd.293802$3l3.275124@attbi_s03... "Chuck" wrote in message news:XrBdd.8254$6P5.7645@okepread02... snip. ... Hi Art, Ok, I'm always open minded to learn something new... Wow,,,...... there are not many people around who could say that !. Since 99.999% of things presented as new are incorrect most experts have determined that the odds favor them if they label EVERYTHING new as in error. If something comes along that is really new they always have the comment ' I knew about that a long while ago" to fall back on. Hi Art, Anyone who believes they know it all, has much to learn :-) ... The program shows that the normal 2 element is not the optimum in that a polygon of vectors beats a triangle of vectors. At the same time with added elements you get diminishing returns in std and conventional forms. The program showed that 1 to 1.5 dbi was available over the standard 2 element on the same length boom.if one could overcome mechanical restraints. (I was comparing to a Beasely example of what gain could be attained for two elements on a 7 foot boom) Now that is not the end of the experiment as I cannot verify the accuracy of the program, because I did not write it, and I certainly cannot say that my modelling aproach is without error since that is what many 'experts' point to if they don't like the results. It was for that reason I asked if any similar data had been made available for boom length by reputable programmers and antenna 'experts' for comparison purposes .., If these initial results were quoted as accurrate there would be howls from all the resident antenna ' experts" and I would immediately be placed in the six foot hole that they have been trying to put you in for the last eight years Art I get the impression that what you are doing is placing any number of elements on a .1 lambda boomlength, in order to determine if the close proximity EM interactions produce more gain than just the standard 2 elements would on that same boomlength. In the optimization process, some of the resulting element diameters are quite small. You're asking if anyone else has looked into this, and if any results have been published. Is this a correct assessment so far? 73 de Chuck, WA7RAI |
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