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#1
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Richard Clark wrote:
wrote: -sigh- even when you offer confirmatory recitations you still miss the details. There are only 11 pages in Application Note 95-1 and the material you describe appears on page 4 not 22. -sigh- The PDF version of HP ap note AN 95-1 contains 79 pages. Simply because they encounter no ill consequence of source mismatch is NOT evidence of the source Z being immaterial to the process of measuring SWR. A source mismatch affects the power available from the source. The SWR does not depend upon the power available from the source. The SWR is the same whether the source is 1% efficient or 99% efficient. Efficiency depends upon Zs. SWR does not. -- 73, Cecil, W5DXP |
#2
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On Fri, 03 Oct 2003 13:49:15 -0500, Cecil Moore
wrote: A source mismatch affects the power available from the source. The SWR does not depend upon the power available from the source. The SWR is the same whether the source is 1% efficient or 99% efficient. Efficiency depends upon Zs. SWR does not. Hi Cecil, So, a source exhibiting 200 Ohms Resistive feeding a 50 Ohm line that is then terminated in a load of 200 Ohms Resistive exhibits what SWR? The absence of a numeric answer is par for the course here. The answer, of course, can be found in Chipman's text but that requires the act of reading, not snipping (which would still be available to the literate). Many here stumble when it comes to measuring SWR employing (in this case) 2 resistors and a hank of line - how they could imagine they respond faithfully to more elaborate enquiries is quite amusing, especially when they argue the Source Z has nothing to do with it. My mental image of that assemblage of pundits is that of them crowded on a small desert isle, each proclaiming it to be a vast, lush continent. Another SWR Don added to that bunch will teeter someone into the brine. ;-) Do any of you know how to tread water? Seems to be the perfect Darwinian thinning mechanism; but in fact most already tread water at high tide. 73's Richard Clark, KB7QHC |
#3
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Richard Clark wrote:
So, a source exhibiting 200 Ohms Resistive feeding a 50 Ohm line that is then terminated in a load of 200 Ohms Resistive exhibits what SWR? Assuming a lossless 50 ohm line, the steady-state SWR is 4:1 no matter what the source impedance (assuming there exists a source voltage not equal to zero volts). Steady-state SWR in a lossless feedline is a constant fixed voltage ratio from end to end. -- 73, Cecil, W5DXP |
#4
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On Fri, 03 Oct 2003 14:58:15 -0500, Cecil Moore
wrote: Richard Clark wrote: So, a source exhibiting 200 Ohms Resistive feeding a 50 Ohm line that is then terminated in a load of 200 Ohms Resistive exhibits what SWR? Assuming a lossless 50 ohm line, the steady-state SWR is 4:1 no matter what the source impedance (assuming there exists a source voltage not equal to zero volts). Steady-state SWR in a lossless feedline is a constant fixed voltage ratio from end to end. Hi Cecil, WRONG! The method of computation you employ violates Chipman and any other of a host of authoritative sources on the topic. If you actually attempted to verify this at the bench you would "perhaps" find it at only one point, or at harmonic distances (wavelength specific) along the line. That means you would stand only a couple of percent chance of that with a random choice. Guesses are not responsive to the intent and no points are awarded. I will leave you to discover Chipman's means to find SWR any where along any line for yourself. You might enjoy the celebrity of being the second to do so. ;-) 73's Richard Clark, KB7QHC |
#5
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Richard Clark wrote:
The method of computation you employ violates Chipman and any other of a host of authoritative sources on the topic. If you actually attempted to verify this at the bench you would "perhaps" find it at only one point, or at harmonic distances (wavelength specific) along the line. -sigh- One cannot verify anything about lossless lines on the bench. The only verifications about lossless lines that are possible have to be done in one's head because that's the only place lossless lines exist. One can come close with open-wire line and extrapolate the results to lossless lines. You see the effects more on coax than on open-wire line simply because coax is lossier than open-wire line. I will leave you to discover Chipman's means to find SWR any where along any line for yourself. You told me to reference page 139 which I did. All that page talks about is lossy feedline with a complex Z0. The purely resistive feedline, given by you in your example, cannot have a complex Z0. So what Chipman has to say is irrelevant to the problem you posed, i.e. purely resistive Z0, purely resistive source impedance, and purely resistive load. You apparently should have posed a complex Z0. Chipman explains perfectly why the measured SWR may vary with a lossy line, i.e. with a complex Z0. There are points of conjugate matching up and down the line where an oscillation takes place. The oscillation causes extra reflections and re-reflections at the conjugate match point, an exchange of a third energy between the capacitive reactance and the inductive reactance at that point, that affects the SWR readings. But such is not possible with the purely resistive Z0 that you posed. -- 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! =----- |
#6
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On Fri, 03 Oct 2003 16:12:48 -0500, Cecil Moore
wrote: One cannot verify anything about lossless lines on the bench. You can't, that's for sure, and not even with a line so short you couldn't measure its loss - so what's the point of arguing lossless? So what Chipman has to say is irrelevant to the problem you posed Hi Cecil, I have already provided quotes, chapter and verse that refute your statement. No point in going further. 73's Richard Clark, KB7QHC |
#7
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Richard Clark wrote:
I have already provided quotes, chapter and verse that refute your statement. Here's a quote from Chipman. "These large reflection coefficients are an example of the phenomenon of 'resonant rise of voltage' in series resonant circuits... The large reflection coefficients are obtained only when the reactance of the load impedance is of opposite sign to the reactance component of the characteristic impedance." You posed a purely resistive Z0. The "resonant rise of voltage" cannot happen with a purely resistive Z0. Would you like to pose a complex Z0? -- 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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