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May 13th 11, 10:44 PM
posted to rec.radio.amateur.antenna
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Transmitter Output Impedance
On May 13, 5:39*pm, walt wrote:
On May 13, 4:09*pm, Cecil Moore wrote: On May 11, 3:09*pm, walt wrote: Cecil, you are correct!!! Thanks Walt, it would be interesting to see what else about which I am correct. W7EL has a food-for-thought publication with one section about reflections from the source. His source has a 50 ohm source impedance, by design, so any dynamic load pulling experiment should result in zero reflections from the source. Question is, does it? http://eznec.com/misc/Food_for_thought.pdf The "forward and reverse power section" is at the bottom of the page. Using the dynamic load pulling method, do the results always indicate 50 ohms for the source impedance no matter what is the load and/or the transmission line length? If not, the method yields invalid results. IMO, it is a gross error to presume that all redistribution of energy is a result of reflections. In W7EL's example, there are no reflections from the source yet it is obvious that energy is being redistributed from the source back toward the load in some cases but not in other cases. IMO, destructive/constructive interference must be taken into account in order to explain the results. Yet, no one except yours truly has even mentioned interference effects as a method of redistributing energy. Anyone interested in understanding the role of interference at impedance discontinuities in transmission lines is welcome to read my article at: http://www.w5dxp.com/energy.htm -- 73, Cecil, w5dxp.com "Halitosis is better than no breath at all.", Don, KE6AJH/SK Right on, Cecil. The article you URL'ed is the most clear and accurate paraphrasing of my presentation of the subject in 'Reflections'. Nowhere else is the subject clearly defined concerning destructive and constructive interference in relation to impedance matching and 100% re-reflection. I hope RF engineers everywhere can realize that optics and RF are indeed using the same principles of electromagnetics, and therefore follow exactly the same rules. However, I would like for you to add one more reference to your article, an article I published in QEX that proves Steve Best's QEX three articles wrong. It appeared in the Jul/Aug 2004 issue, entitled, "A tutorial Dispelling Certain Misconceptions Concerning Wave Interference In Impedance Matching." Let me know here whether you have a copy of my QEX article. If not, I'll email you a copy. Walt, W2DU If anyone else on this thread would like a copy of my QEX article please let me know by email. My email address is shown above. Sorry guys, my error, my email address is . Walt |
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