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#1
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I believe that "Mother Nature's" voltage reflection coefficient is the well
known classical one, i.e. rho = (Z - Zo)/(Z + Zo) is "Mother Nature's" reflection coefficient. I believe this simply because it corresponds to the "image match"! i.e. rho will be null when Z = Zo [NOT conj(Zo)], and is the condition for there to be no reflected voltage wave. Note: this is *NOT* the condition for a "conjugate match" i.e. maximum power transfer does not result in a null voltage refelection coefficient in the case of a general complex surge impedance Zo. As a "thought experiment" to support my contention that rho = (Z - Zo)/(Z + Zo) Is "natural", consider the case of an infinitely long transmission line of surge impedance [characteristic impedance] Zo, where in general Zo may be complex and not necessarily a real constant e.g. [Zo is not 50 Ohms resistive or some other such simple case.] i.e. Zo = Zo(p) = sqrt((R + pL)/(G + pC)) Where, R, L, G and C are the primary parameters of the line and p is the complex frequency p = s + jw and the value of Zo is complex in general and may vary with frequency p. In this thought experiment consider that you are standing in the "center" of this infinitely long line of surge impedance Zo and that you cut said line with a pair of pliers. Looking in one direction down the semi-infinite line you see a driving point impedance equal to the surge impedance Zo of that semi-infinite line. Looking in the other direction you will also see a driving point impedance equal to the surge impedance Zo of a semi-infinite line. And so... at the cut you have made, there is an "image match". i.e. at the cut two equal driving point impedances Zo are facing each other. This is a Zo match, or "image match", it is not a conjugate match! In a conjugate match Zo would be facing conj(Zo). Now solder the cut back together and then consider a "wave" launched from one end of this infinite line in one direction. If you have trouble picturing this situation just imagine it is Douglas Adams sitting on the patio of the Restaurant at the End of the Universe with his handy wave generator who launches the wave! Such a wave will move in one direction only on down that Zo line forever and will never be reflected because there are no discontinuities over that infinite distance. Now as the wave is passing the "cut" that you made in the center of that infinite line, quickly insert a reflectometer with internal reference impedance R = Zo, the characteristic surge impedance of the line. This reflectometer will read a rho of: rho = (Z - Zo)/(Z + Zo) Where, since one sees Zo in both directions at the cut and so Z = Zo and rho = 0, as it should of course indicate zero reflected voltage since there are no "reflections" on this infinite line with a wave travelling in only one direction. This is a very natural situation... And so I maintain that "Mother Nature" favors the *definition* rho = (Z - Zo)/(Z + Zo) or as I like to write it rho = (Z - R)/(Z + R) since I like to use R representing the [R]eference impedance i.e. R = Zo because R is the [R]eference impedance used inside the reflectometer and whichmay or may not be equal to Zo as appropriate for the intended use. I have no problem whatsoever with this definition of rho not being null when there is a conjugate match. In the general case for "Mother Nature's" reflection coefficient rho will not be zero when there is maximum power transfer. In fact there may well be considerable reflected VAR's in that case... VAR's being Volt Amperes Reactive, i.e. reactive power reflected at the conjugate match point. On the other hand, I have no argument with those who choose to define rho as: rho = (Z - conj(Zo))/(Z + conj(Zo)) just as long as they are consistent in it's use and the conclusions they draw from it. Here they will get a null rho for a conjugate match, and they will not get a null rho for an image match. I can see situations in which such a defintion of rho using conj(Zo) might be useful, not necessary mind you, but perhaps more convenient for solving some problems. But I still maintain that defining rho in terms of the conjugate of Zo is "unatural" and that "Mother Nature" naturally likes the classical... rho = (Z - Zo)/(Z + Zo) because that is what she uses herself when she supports the natural propagation of waves on transmission lines. Thoughts, comments? -- Peter K1PO Indialantic By-the-Sea, FL. -- Peter K1PO Indialantic By-the-Sea, FL. |
#2
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![]() But I still maintain that defining rho in terms of the conjugate of Zo is "unatural" and that "Mother Nature" naturally likes the classical... rho = (Z - Zo)/(Z + Zo) because that is what she uses herself when she supports the natural propagation of waves on transmission lines. Thoughts, comments? -- Peter K1PO Indialantic By-the-Sea, FL. Do you ever notice the fleeting look of fear on the faces of people as they suddenly recognize you as you walk down the street, Peter? 73, Tom Donaly, KA6RUH |
#3
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Tom:
[snip] Do you ever notice the fleeting look of fear on the faces of people as they suddenly recognize you as you walk down the street, Peter? 73, Tom Donaly, KA6RUH [snip] Yes!!! Finally I'm recognized for what I am... The Darth Vader of USENET. Thanks, -- Peter K1PO Indialantic By-the-Sea, FL |
#4
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On Tue, 26 Aug 2003 06:24:17 GMT, "Peter O. Brackett"
wrote: Yes!!! Finally I'm recognized for what I am... The Darth Vader of USENET. Hi Darth, When you run across your son, please keep it a family secret. 73's Richard Clark, KB7QHC |
#5
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Richard:
[snip] "Richard Clark" wrote in message ... On Tue, 26 Aug 2003 06:24:17 GMT, "Peter O. Brackett" wrote: Yes!!! Finally I'm recognized for what I am... The Darth Vader of USENET. Hi Darth, When you run across your son, please keep it a family secret. 73's Richard Clark, KB7QHC [snip] Actually I have two sons [That I know of?] which one do you refer to, the "good" one or the "evil" one? One som lives in Seattle [Tim], the other in San Francisco [Steve]... both are inactive hams, both think I'm far too old and... irrelevant anyway. Sigh... My wife gives me no respect, my sons give me no respect, the only respect I get is from the denziens of this Newsgroup, and even then it's only when I attempt to "terrorize" the group with tidbits of algebra! :-) What? -- Peter K1PO Indialantic By-the-Sea, FL. |
#6
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My wife gives me no respect, my sons give me no respect, the only
respect I get is from the denziens of this Newsgroup, and even then it's only when I attempt to "terrorize" the group with tidbits of algebra! :-) What? -- Peter K1PO Indialantic By-the-Sea, FL. Canucks in exile rspect you tremendously. You would get even more respect if you can proclaim Indialantic new DXCC entity. Does it have to do anything with Indians, Indiana Jones, in Diana, Atlantis, dial, In Dial Antic or what? Yuri da BUm in BMV (Buick really) by the see (if he can make it) |
#7
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On Wed, 27 Aug 2003 21:19:47 GMT, "Peter O. Brackett"
wrote: Well Indialantic By-the-Sea is a small town [pop ~2500] on the barrier island about .... Hi Peter, And I thought it was there because it wasn't Indipacific or Indigulf. 73's Richard Clark, KB7QHC |
#8
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![]() And I thought it was there because it wasn't Indipacific or Indigulf. 73's Richard Clark, KB7QHC Must be bacause of them reflected waves? Maybe bunch of dummies on the beach would calm things down, like 1:1 :-) Sounds like radio paradise Peter. We almost bought island in Maine, only to find that there was erosion going on and environazis were oposed to any shoring up of private property. It was like a dream, at the end of peninsula, separated by abt 200 ft channel which would emerge at low tide and allow Jeep to get through. Power and telephone feeding two cottages (low and high band), oh well! Found another place at Cape Breton, I hope to fire up from there in some contests, it is a park I believe. 73 Yuri |
#9
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Yuri:
[snip] Sounds like radio paradise Peter. We almost bought island in Maine, only to find that there was erosion going on and environazis were oposed to any shoring up of private property. It was like a dream, at the end of peninsula, separated by abt 200 ft channel which would emerge at low tide and allow Jeep to get through. Power and telephone feeding two cottages (low and high band), oh well! Found another place at Cape Breton, I hope to fire up from there in some contests, it is a park I believe. 73 Yuri [snip] We too have a Nova Scotia place [a condo] on the Halifax waterfront but I don't have any antennas up there yet either. I hope to have antennas up in both places, i.e. Indialantic and Halifax probably later in the New Year. My current radio hobby project, fitting it in between consulting jobs. I'm supposed to be fully retired but find that I am only semi-retired :-). is to outfit my Expedition with an IC-706 and a Tarheels screwdriver both of which I bought just after Dayton. But I haven't even drilled holes in the Expedition yet. Procrastination is ruining my hobby! I've never been HF mobile, wanted to try that. I was thinking I might like to try some DXpeditioning now that I am supposed to have the time. Sigh. -- Peter K1PO [ex VE1AEX, VE3DZK, VE2POB] Indialantic By-the-Sea, FL. |
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