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#2
October 14th 14, 07:41 PM
posted to rec.radio.amateur.antenna
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The catenary effect
John S wrote:
On 10/14/2014 12:18 PM, wrote: John S wrote: On 10/13/2014 12:38 PM, wrote: John S wrote: Jim is right. There is almost no difference in a V and a catenary as far as the antenna is concerned. It would really wind up being an exercise of "can we really model a catenary?" If anyone disagrees, we will do it. (NOTE: I said "we", not just me) It depends on how close you want the model to be, but in general all you do is break the catenary, or any curve you want, into a series of straight line segments. Yes, of course. And, with the free version of EZNEC, one must be careful not to exceed the max segments allowed. Not really a problem as it does not take many segments to represent the ends, which has a slow change, as the center part with a more rapid change. If I were going to do it, I would use something like a spreadsheet to plot the curve then draw straight line segments on the curve and plug those directly into EZNEC. Interestin that you suggest that. See below. Note that I am not affiliated with EZNEC in anyway other than as a very satisfied user. The extreme case is modeling a loop as a geometric figure with straight side. EZNEC will generate loops with whatever number of sides you want and thus it is fairly easy to see when increasing the number of sides gives diminishing returns in the difference between the loops. While checking the EZNEC Web site to see if I had the latest version two days ago, I discovered a dynamite Excel spreadsheet application. It is called AutoEZ. Just today I learned how to use it to generate a curve of antenna efficiency vs permeability of the wire. I also was able to reproduce the list I posted earlier of efficiency vs antenna length in a matter of seconds. I am flabbergasted with this tool. It seems to have an optimize tool that I have yet to explore. There is a free version with limitations. Yeah, I am aware of it and have been concidering buying it. The rub is I would also have to buy Excel and the machine I run EZNEC on only has OpenOffice and then only to read the occasional Microsoft file. -- Jim Pennino |
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#3
October 14th 14, 07:50 PM
posted to rec.radio.amateur.antenna
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The catenary effect
On 10/14/2014 1:41 PM, wrote:
John S wrote: On 10/14/2014 12:18 PM, wrote: John S wrote: On 10/13/2014 12:38 PM, wrote: John S wrote: Jim is right. There is almost no difference in a V and a catenary as far as the antenna is concerned. It would really wind up being an exercise of "can we really model a catenary?" If anyone disagrees, we will do it. (NOTE: I said "we", not just me) It depends on how close you want the model to be, but in general all you do is break the catenary, or any curve you want, into a series of straight line segments. Yes, of course. And, with the free version of EZNEC, one must be careful not to exceed the max segments allowed. Not really a problem as it does not take many segments to represent the ends, which has a slow change, as the center part with a more rapid change. If I were going to do it, I would use something like a spreadsheet to plot the curve then draw straight line segments on the curve and plug those directly into EZNEC. Interestin that you suggest that. See below. Note that I am not affiliated with EZNEC in anyway other than as a very satisfied user. The extreme case is modeling a loop as a geometric figure with straight side. EZNEC will generate loops with whatever number of sides you want and thus it is fairly easy to see when increasing the number of sides gives diminishing returns in the difference between the loops. While checking the EZNEC Web site to see if I had the latest version two days ago, I discovered a dynamite Excel spreadsheet application. It is called AutoEZ. Just today I learned how to use it to generate a curve of antenna efficiency vs permeability of the wire. I also was able to reproduce the list I posted earlier of efficiency vs antenna length in a matter of seconds. I am flabbergasted with this tool. It seems to have an optimize tool that I have yet to explore. There is a free version with limitations. Yeah, I am aware of it and have been concidering buying it. The rub is I would also have to buy Excel and the machine I run EZNEC on only has OpenOffice and then only to read the occasional Microsoft file. Bummer! You don't seem to suffer from it, though. |
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#4
October 14th 14, 08:19 PM
posted to rec.radio.amateur.antenna
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The catenary effect
John S wrote:
On 10/14/2014 1:41 PM, wrote: John S wrote: On 10/14/2014 12:18 PM, wrote: John S wrote: On 10/13/2014 12:38 PM, wrote: John S wrote: Jim is right. There is almost no difference in a V and a catenary as far as the antenna is concerned. It would really wind up being an exercise of "can we really model a catenary?" If anyone disagrees, we will do it. (NOTE: I said "we", not just me) It depends on how close you want the model to be, but in general all you do is break the catenary, or any curve you want, into a series of straight line segments. Yes, of course. And, with the free version of EZNEC, one must be careful not to exceed the max segments allowed. Not really a problem as it does not take many segments to represent the ends, which has a slow change, as the center part with a more rapid change. If I were going to do it, I would use something like a spreadsheet to plot the curve then draw straight line segments on the curve and plug those directly into EZNEC. Interestin that you suggest that. See below. Note that I am not affiliated with EZNEC in anyway other than as a very satisfied user. The extreme case is modeling a loop as a geometric figure with straight side. EZNEC will generate loops with whatever number of sides you want and thus it is fairly easy to see when increasing the number of sides gives diminishing returns in the difference between the loops. While checking the EZNEC Web site to see if I had the latest version two days ago, I discovered a dynamite Excel spreadsheet application. It is called AutoEZ. Just today I learned how to use it to generate a curve of antenna efficiency vs permeability of the wire. I also was able to reproduce the list I posted earlier of efficiency vs antenna length in a matter of seconds. I am flabbergasted with this tool. It seems to have an optimize tool that I have yet to explore. There is a free version with limitations. Yeah, I am aware of it and have been concidering buying it. The rub is I would also have to buy Excel and the machine I run EZNEC on only has OpenOffice and then only to read the occasional Microsoft file. Bummer! You don't seem to suffer from it, though. Until AutoEZ I haven't found anything I can't do with OpenOffice. My main interest in AutoEZ is the ability to change things and plot the data. Examples: You model a reflector as a number of wires. How close do the wires have to be in wvelengths to approximate a solid reflector? You model a beam consisting of double diamond structures. How does the gain, impedance, and F/B vary with reflector size and spacing? While you can do both manually, it is a bit arduaous. -- Jim Pennino |
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#5
October 14th 14, 08:54 PM
posted to rec.radio.amateur.antenna
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The catenary effect
On 10/14/2014 2:19 PM, wrote:
John S wrote: On 10/14/2014 1:41 PM, wrote: John S wrote: On 10/14/2014 12:18 PM, wrote: John S wrote: On 10/13/2014 12:38 PM, wrote: John S wrote: Jim is right. There is almost no difference in a V and a catenary as far as the antenna is concerned. It would really wind up being an exercise of "can we really model a catenary?" If anyone disagrees, we will do it. (NOTE: I said "we", not just me) It depends on how close you want the model to be, but in general all you do is break the catenary, or any curve you want, into a series of straight line segments. Yes, of course. And, with the free version of EZNEC, one must be careful not to exceed the max segments allowed. Not really a problem as it does not take many segments to represent the ends, which has a slow change, as the center part with a more rapid change. If I were going to do it, I would use something like a spreadsheet to plot the curve then draw straight line segments on the curve and plug those directly into EZNEC. Interestin that you suggest that. See below. Note that I am not affiliated with EZNEC in anyway other than as a very satisfied user. The extreme case is modeling a loop as a geometric figure with straight side. EZNEC will generate loops with whatever number of sides you want and thus it is fairly easy to see when increasing the number of sides gives diminishing returns in the difference between the loops. While checking the EZNEC Web site to see if I had the latest version two days ago, I discovered a dynamite Excel spreadsheet application. It is called AutoEZ. Just today I learned how to use it to generate a curve of antenna efficiency vs permeability of the wire. I also was able to reproduce the list I posted earlier of efficiency vs antenna length in a matter of seconds. I am flabbergasted with this tool. It seems to have an optimize tool that I have yet to explore. There is a free version with limitations. Yeah, I am aware of it and have been concidering buying it. The rub is I would also have to buy Excel and the machine I run EZNEC on only has OpenOffice and then only to read the occasional Microsoft file. Bummer! You don't seem to suffer from it, though. Until AutoEZ I haven't found anything I can't do with OpenOffice. My main interest in AutoEZ is the ability to change things and plot the data. Examples: You model a reflector as a number of wires. How close do the wires have to be in wvelengths to approximate a solid reflector? Good point. I've heard that .1 lambda is sufficient. I would normally use half that. The best way to know is to model it. You model a beam consisting of double diamond structures. How does the gain, impedance, and F/B vary with reflector size and spacing? One of the examples in AutoEZ is just that. While you can do both manually, it is a bit arduaous. Indeed. I have a ways to go to be able to do that with AutoEZ, but I'm sure it will come with practice. |
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