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#1
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reciprocity and program zl_zin ??
The program zl_zin calculates a Zload from a known Zin. It would seem that given
a symmetrical feedline that Zin and Zload should be mirrors. Why is that not so? Is there a program that will calculate Zin from a known Zload? Thanks - Dan kb0qil |
#2
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reciprocity and program zl_zin ??
dansawyeror wrote:
The program zl_zin calculates a Zload from a known Zin. It would seem that given a symmetrical feedline that Zin and Zload should be mirrors. Why is that not so? I'm not sure what you mean by "mirrors". But the relationship between Zin and Zload is dictated by the way transmission lines transform impedances. A better question is, why should it be anything else? A series inductor is symmetrical, is it not? Suppose you have a series inductor with impedance +j10 ohms in a box. Connect it to a load of 50 + j0 ohms. Looking into the input of the series inductor, you see 50 + j10 ohms. Now put a load of 50 + j10 ohms at the output instead of 50 + j0. Are you saying you expect to see 50 + j0 at the input? Why? Is there a program that will calculate Zin from a known Zload? Hopefully someone else will be able to answer that. Roy Lewallen, W7EL |
#3
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reciprocity and program zl_zin ??
On Fri, 23 Dec 2005 15:46:16 -0800, dansawyeror
wrote: The program zl_zin calculates a Zload from a known Zin. It would seem that given a symmetrical feedline that Zin and Zload should be mirrors. Why is that not so? Line loss. Is there a program that will calculate Zin from a known Zload? http://www.vk1od.net/tl/tllce.php will work both ways, Zin from Zload, and Zload from Zin. Owen Thanks - Dan kb0qil -- |
#4
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reciprocity and program zl_zin ??
Roy,
Well the intuition was correct, however the problem is one level more complex. The Smith chart shows the following approximate 'mirror' relationships for j=0: Load Input Measurement 20 125 25 100 35 71 10 250 50 50 It is a "log" mirror centered on 50 Ohms. The mirror relationship holds for j /= 0, however the calculation is more complex. - Dan Roy Lewallen wrote: dansawyeror wrote: The program zl_zin calculates a Zload from a known Zin. It would seem that given a symmetrical feedline that Zin and Zload should be mirrors. Why is that not so? I'm not sure what you mean by "mirrors". But the relationship between Zin and Zload is dictated by the way transmission lines transform impedances. A better question is, why should it be anything else? A series inductor is symmetrical, is it not? Suppose you have a series inductor with impedance +j10 ohms in a box. Connect it to a load of 50 + j0 ohms. Looking into the input of the series inductor, you see 50 + j10 ohms. Now put a load of 50 + j10 ohms at the output instead of 50 + j0. Are you saying you expect to see 50 + j0 at the input? Why? Is there a program that will calculate Zin from a known Zload? Hopefully someone else will be able to answer that. Roy Lewallen, W7EL |
#5
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reciprocity and program zl_zin ??
On Fri, 23 Dec 2005 15:46:16 -0800, dansawyeror
wrote: The program zl_zin calculates a Zload from a known Zin. It would seem that given a symmetrical feedline that Zin and Zload should be mirrors. Why is that not so? Line loss (if I understand your question correctly) Is there a program that will calculate Zin from a known Zload? http://www.vk1od.net/tl/tllce.php will work both ways, Zin from Zload, and Zload from Zin. Owen Thanks - Dan kb0qil -- |
#6
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reciprocity and program zl_zin ??
Is there a program that will calculate Zin from a known Zload?
========================================== Yes, from the same place you obtained program ZL_ZIN. For coax lines use program COAXPAIR. For balanced twin lines use programs RJELINE3 or 4. These programs are to professional standards, 1% accuracy or better, covering the frequency range from audio to UHF. ---- .................................................. .......... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp .................................................. .......... |
#7
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reciprocity and program zl_zin ??
On Fri, 23 Dec 2005 16:10:01 -0800, Roy Lewallen
wrote: dansawyeror wrote: The program zl_zin calculates a Zload from a known Zin. It would seem that given a symmetrical feedline that Zin and Zload should be mirrors. Why is that not so? I'm not sure what you mean by "mirrors". But the relationship between Zin and Zload is dictated by the way transmission lines transform impedances. A better question is, why should it be anything else? Roy, I also wasn't quite sure of the concept of *symmetry* and *mirror* as used by Dan. I made the assumption (perhaps incorrectly) that the transformation is symmetrical for an integral number of half waves of lossless transmission line. Impedances might be seen to "mirror" (if mirror means an exact copy) for an integral number of half waves of lossless line. Having made that assumption, loss introduces errors to the "mirroring", and line lengths other than an integral number of quarter waves aren't symmetrical in that sense. Having read Dan's further comments, it seems he thought any length of real line was symmetric as an impedance transformer. It might be that you can swap A and B ends in a circuit and obtain the same behaviour, but you can't swap Zload and Zin in the general case. Dan, the terms you have used don't have common usage in this context, and confuse the issue. Owen -- |
#8
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reciprocity and program zl_zin ??
dansawyeror wrote:
Roy, Well the intuition was correct, however the problem is one level more complex. The Smith chart shows the following approximate 'mirror' relationships for j=0: Load Input Measurement 20 125 25 100 35 71 10 250 50 50 It is a "log" mirror centered on 50 Ohms. The mirror relationship holds for j /= 0, however the calculation is more complex. - Dan Well, yes, you can find specific relationships for various special cases of load impedance and line length, particularly if you assume zero loss. But only the appropriate equations, derived from basic principles, will give you the correct relationship in the general case. Be wary of oversimplification. Roy Lewallen, W7EL |
#9
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reciprocity and program zl_zin ??
On Sat, 24 Dec 2005 01:35:01 GMT, Owen Duffy wrote:
I made the assumption (perhaps incorrectly) that the transformation is symmetrical for an integral number of half waves of lossless transmission line. Impedances might be seen to "mirror" (if mirror means an exact copy) for an integral number of half waves of lossless line. That should have read: I made the assumption (perhaps incorrectly) that the transformation is symmetrical for an integral number of *quarter* waves of lossless transmission line. Impedances might be seen to "mirror" (if mirror means an exact copy) for an integral number of half waves of lossless line. Owen -- |
#10
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reciprocity and program zl_zin ??
Thanks,
Can you explain "transmission performance". Is it as measured and the source, Zin? What is the range of Reflection Coeff? Is it a percentage? Is refl. coeff. angle measured at Input? Thanks, Dan Reg Edwards wrote: Is there a program that will calculate Zin from a known Zload? ========================================== Yes, from the same place you obtained program ZL_ZIN. For coax lines use program COAXPAIR. For balanced twin lines use programs RJELINE3 or 4. These programs are to professional standards, 1% accuracy or better, covering the frequency range from audio to UHF. ---- .................................................. ......... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp .................................................. ......... |