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#1
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On May 24, 10:31*pm, lu6etj wrote:
Anyway, my question is about validity of the assertion that reflected wave -in that example- IS ABSORBED by the pad. According to my simple calculations this hipothesis, as I see it, it does not coincide with my early learnings. Miguel, let's switch your example over to an easier to understand example. Assume an ideal signal generator equipped with a resistive circulator load. Let's call such a device an SGCR, a Signal Generator equipped with a Circulator and a Resistor. Assume that 100% of the reflected energy is dissipated in the circulator load resistor (none re-reflected) and none of the reflected energy reaches the source. So here is the block diagram. SGCR--------feedline--------load That model should be easier to discuss than the pad attenuator model. What do you think? -- 73, Cecil, w5dxp.com |
#2
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On 25 mayo, 11:49, Cecil Moore wrote:
On May 24, 10:31*pm, lu6etj wrote: Anyway, my question is about validity of the assertion that reflected wave -in that example- IS ABSORBED by the pad. According to my simple calculations this hipothesis, as I see it, it does not coincide with my early learnings. Miguel, let's switch your example over to an easier to understand example. Assume an ideal signal generator equipped with a resistive circulator load. Let's call such a device an SGCR, a Signal Generator equipped with a Circulator and a Resistor. Assume that 100% of the reflected energy is dissipated in the circulator load resistor (none re-reflected) and none of the reflected energy reaches the source. So here is the block diagram. SGCR--------feedline--------load That model should be easier to discuss than the pad attenuator model. What do you think? -- 73, Cecil, w5dxp.com Excuse me Cecil: I am reading this newsgroup through Google groups web page and I just realized that later replies to previous post are intercalated in the thread, while I expected to see it always at the end of it, for that reason I did not ACK before to it. (I hope yours be the only one, I will review all thread tho chek for others). In a early post I wrote = "of course if we insert a circulator to separate both powers, generator now would see 1 ohm load, could develope 1 W incident, 0 W reflected (Pn=1W) on circulator input, 0.36 W would be outputting on the other port to render 0.64 W (Pn) to the load with 1 W Pf and 0,36 W Pr again" Is this result OK for you?. The thread advance toward more deeper issues since :), and now I have been analizing all the matter because it quickly superceed my original doubt. A few minutes ago had started to read your article (http:// www.w5dxp.com/energy.htm) and the Roy's one (http://eznec.com/misc/ Food_for_thought.pdf) and yesterday I have been reloading my old "Transmission lines antennas and wave guides" from King, Mimno & Wing to review the issue from that classical perspective. I am interested in your optic analogy, I can imagine the load as a partially reflecting surface, real part of it as absorbance (transmittance if it was a radiator). line as a unidimensional medium and reflection as the form of "redistribute energy" (is it OK?) and a coherent light source for the voltage source, but I am still trying to visualze the optical equivalent of source resistance and its job to be a good analog, Also I am interested in check other values and conditions in your other article (first part) with 45 degree line. Thank you very much for your helping and inspiration. 73 - Miguel LU6ETJ |
#3
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On May 27, 9:50*am, lu6etj wrote:
I am reading this newsgroup through Google groups web page and I just realized that later replies to previous post are intercalated in the thread, while I expected to see it always at the end of it, for that reason I did not ACK before to it. (I hope yours be the only one, I will review all thread tho chek for others). I am also using Google since ATT dropped Usenet. I liked Thunderbird a lot better than Google's usenet interface but I am adapting. The above information is good to know. Thunderbird has a way to keep up with unread vs read postings but Google doesn't seem to - at least I don't know how to do it on Google. In a early post I wrote = "of course if we insert a circulator to separate both powers, generator now would see 1 ohm load, could develope 1 W incident, 0 W reflected (Pn=1W) on circulator input, 0.36 W would be outputting on the other port to render 0.64 W (Pn) to the load with 1 W Pf and 0,36 W Pr again" Is this result OK for you?. The SGCR source is usually designed for 50 ohms, i.e. the signal generator always "sees" a 50 ohm load because it does not "see" any reflected energy. The ideal circulator is usually designed with 50 ohm line and a 50 ohm load resistor. If we could stick with that particular configuration for the SGCR source, it would aid in my understanding what is the actual system configuration, i.e. not your fault but I am confused by your above posting. I am interested in your optic analogy, I can imagine the load as a partially reflecting surface, real part of it as absorbance (transmittance if it was a radiator). line as a unidimensional medium and reflection as the form of "redistribute energy" (is it OK?) and a coherent light source for the voltage source, but I am still trying to visualze the optical equivalent of source resistance and its job to be a good analog, Also I am interested in check other values and conditions in your other article (first part) with 45 degree line. I don't think a laser source handles reflected energy like an RF amp does. So, to start with, let's avoid reflected energy being incident upon the laser source. Here is a good example to start with, a 1/4WL non-reflective coating on glass. Laser-----air-------|--1/4WL thin-film, r = 1.2222---|---Glass, r = 1.4938---... The 1/4WL thin-film coating on the glass acts exactly like a 1/4WL matching section of transmission line. Reflections at the air to thin- film interface are eliminated by wave cancellation just as the FSU web page says, micro.magnet.fsu.edu/primer/java/scienceopticsu/interference/ waveinteractions/index.html "... when two waves of equal amplitude and wavelength that are 180- degrees ... out of phase with each other meet, they are not actually annihilated, ... All of the photon energy present in these waves must somehow be recovered or redistributed in a new direction, according to the law of energy conservation ... Instead, upon meeting, the photons are redistributed to regions that permit constructive interference, so the effect should be considered as a redistribution of light waves and photon energy rather than the spontaneous construction or destruction of light." Note that the reflection coefficient, r, is 1.0 for air. Thus the SQRT[(1.0)(1.4938)] = 1.2222 ensures that reflections are eliminated by the r = 1.2222 thin-film coating. The same thing happens at the '+' Z0-match in the following RF system. XMTR---50 ohm coax---+---1/4WL 300 ohm feedline---1800 ohm load Note that SQRT[(50)(1800)] = 300 ensuring that reflections are eliminated. -- 73, Cecil, w5dxp.com |
#4
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On 27 mayo, 12:34, Cecil Moore wrote:
On May 27, 9:50*am, lu6etj wrote: I am reading this newsgroup through Google groups web page and I just realized that later replies to previous post are intercalated in the thread, while I expected to see it always at the end of it, for that reason I did not ACK before to it. (I hope yours be the only one, I will review all thread tho chek for others). I am also using Google since ATT dropped Usenet. I liked Thunderbird a lot better than Google's usenet interface but I am adapting. The above information is good to know. Thunderbird has a way to keep up with unread vs read postings but Google doesn't seem to - at least I don't know how to do it on Google. In a early post I wrote = "of course if we insert a circulator to separate both powers, generator now would see 1 ohm load, could develope 1 W incident, 0 W reflected (Pn=1W) on circulator input, 0.36 W would be outputting on the other port to render 0.64 W (Pn) to the load with 1 W Pf and 0,36 W Pr again" Is this result OK for you?. The SGCR source is usually designed for 50 ohms, i.e. the signal generator always "sees" a 50 ohm load because it does not "see" any reflected energy. The ideal circulator is usually designed with 50 ohm line and a 50 ohm load resistor. If we could stick with that particular configuration for the SGCR source, it would aid in my understanding what is the actual system configuration, i.e. not your fault but I am confused by your above posting. I am interested in your optic analogy, I can imagine the load as a partially reflecting surface, real part of it as absorbance (transmittance if it was a radiator). line as a unidimensional medium and reflection as the form of "redistribute energy" (is it OK?) and a coherent light source for the voltage source, but I am still trying to visualze the optical equivalent of source resistance and its job to be a good analog, Also I am interested in check other values and conditions in your other article (first part) with 45 degree line. I don't think a laser source handles reflected energy like an RF amp does. So, to start with, let's avoid reflected energy being incident upon the laser source. Here is a good example to start with, a 1/4WL non-reflective coating on glass. Laser-----air-------|--1/4WL thin-film, r = 1.2222---|---Glass, r = 1.4938---... The 1/4WL thin-film coating on the glass acts exactly like a 1/4WL matching section of transmission line. Reflections at the air to thin- film interface are eliminated by wave cancellation just as the FSU web page says, micro.magnet.fsu.edu/primer/java/scienceopticsu/interference/ waveinteractions/index.html "... when two waves of equal amplitude and wavelength that are 180- degrees ... out of phase with each other meet, they are not actually annihilated, ... All of the photon energy present in these waves must somehow be recovered or redistributed in a new direction, according to the law of energy conservation ... Instead, upon meeting, the photons are redistributed to regions that permit constructive interference, so the effect should be considered as a redistribution of light waves and photon energy rather than the spontaneous construction or destruction of light." Note that the reflection coefficient, r, is 1.0 for air. Thus the SQRT[(1.0)(1.4938)] = 1.2222 ensures that reflections are eliminated by the r = 1.2222 thin-film coating. The same thing happens at the '+' Z0-match in the following RF system. XMTR---50 ohm coax---+---1/4WL 300 ohm feedline---1800 ohm load Note that SQRT[(50)(1800)] = 300 ensuring that reflections are eliminated. -- 73, Cecil, w5dxp.com May we advance in little steps to ensure we share basic assumptions? 1) I did not think of (or is think on?) a laser source, I was one step before, I think only of a "coherent" source to match monofrequency simple AC generator analogy. 2) What would be Rs optical analog? 3) Superposition is a medium phenomenon ¿yes?, for example "eter". Interference an result of it on a other "thing", for example photographic plate or screen. Are we agree? K |
#5
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On May 27, 9:10*pm, lu6etj wrote:
On 27 mayo, 12:34, Cecil Moore wrote: On May 27, 9:50*am, lu6etj wrote: I am reading this newsgroup through Google groups web page and I just realized that later replies to previous post are intercalated in the thread, while I expected to see it always at the end of it, for that reason I did not ACK before to it. (I hope yours be the only one, I will review all thread tho chek for others). I am also using Google since ATT dropped Usenet. I liked Thunderbird a lot better than Google's usenet interface but I am adapting. The above information is good to know. Thunderbird has a way to keep up with unread vs read postings but Google doesn't seem to - at least I don't know how to do it on Google. In a early post I wrote = "of course if we insert a circulator to separate both powers, generator now would see 1 ohm load, could develope 1 W incident, 0 W reflected (Pn=1W) on circulator input, 0..36 W would be outputting on the other port to render 0.64 W (Pn) to the load with 1 W Pf and 0,36 W Pr again" Is this result OK for you?. The SGCR source is usually designed for 50 ohms, i.e. the signal generator always "sees" a 50 ohm load because it does not "see" any reflected energy. The ideal circulator is usually designed with 50 ohm line and a 50 ohm load resistor. If we could stick with that particular configuration for the SGCR source, it would aid in my understanding what is the actual system configuration, i.e. not your fault but I am confused by your above posting. I am interested in your optic analogy, I can imagine the load as a partially reflecting surface, real part of it as absorbance (transmittance if it was a radiator). line as a unidimensional medium and reflection as the form of "redistribute energy" (is it OK?) and a coherent light source for the voltage source, but I am still trying to visualze the optical equivalent of source resistance and its job to be a good analog, Also I am interested in check other values and conditions in your other article (first part) with 45 degree line. I don't think a laser source handles reflected energy like an RF amp does. So, to start with, let's avoid reflected energy being incident upon the laser source. Here is a good example to start with, a 1/4WL non-reflective coating on glass. Laser-----air-------|--1/4WL thin-film, r = 1.2222---|---Glass, r = 1.4938---... The 1/4WL thin-film coating on the glass acts exactly like a 1/4WL matching section of transmission line. Reflections at the air to thin- film interface are eliminated by wave cancellation just as the FSU web page says, micro.magnet.fsu.edu/primer/java/scienceopticsu/interference/ waveinteractions/index.html "... when two waves of equal amplitude and wavelength that are 180- degrees ... out of phase with each other meet, they are not actually annihilated, ... All of the photon energy present in these waves must somehow be recovered or redistributed in a new direction, according to the law of energy conservation ... Instead, upon meeting, the photons are redistributed to regions that permit constructive interference, so the effect should be considered as a redistribution of light waves and photon energy rather than the spontaneous construction or destruction of light." Note that the reflection coefficient, r, is 1.0 for air. Thus the SQRT[(1.0)(1.4938)] = 1.2222 ensures that reflections are eliminated by the r = 1.2222 thin-film coating. The same thing happens at the '+' Z0-match in the following RF system. XMTR---50 ohm coax---+---1/4WL 300 ohm feedline---1800 ohm load Note that SQRT[(50)(1800)] = 300 ensuring that reflections are eliminated. -- 73, Cecil, w5dxp.com May we advance in little steps to ensure we share basic assumptions? 1) I did not think of (or is think on?) a laser source, I was one step before, I think only of a "coherent" source to match monofrequency simple AC generator analogy. 2) What would be Rs optical analog? 3) Superposition is a medium phenomenon ¿yes?, for example "eter". Interference an result of it on a other "thing", for example photographic plate or screen. Are we agree? K |
#6
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On Thu, 27 May 2010 19:10:41 -0700 (PDT), lu6etj
wrote: 2) What would be Rs optical analog? Superman's cataracts with his xray vision. This is probably going to be your only direct answer. 73's Richard Clark, KB7QHC |
#7
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On 28 mayo, 03:18, Richard Clark wrote:
On Thu, 27 May 2010 19:10:41 -0700 (PDT), lu6etj wrote: 2) What would be Rs optical analog? Superman's cataracts with his xray vision. *This is probably going to be your only direct answer. 73's Richard Clark, KB7QHC OK, good example. Cataracts presents absortion, transmission and reflection (they are whitish). To be analog I think should not have reflection. What do you think? (Perhaps seems maieutics but really I am trying to put my thoughts in order at first). What about the third point? I consider it important because light waves are in three dimensional space, so when they cancels in a region, reinforces in other and I can understand redistribution, but line travelling waves are in unidimensional space and here I can not visualize (realize?) the energy redistribution as in light interference. Sorry, when I put interrogation words inside parentheses is that I am not sure the better/adecuated translation. 73 Miguel Ghezzi LU6ETJ |
#8
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On 28 mayo, 05:47, lu6etj wrote:
On 28 mayo, 03:18, Richard Clark wrote: On Thu, 27 May 2010 19:10:41 -0700 (PDT), lu6etj wrote: 2) What would be Rs optical analog? Superman's cataracts with his xray vision. *This is probably going to be your only direct answer. 73's Richard Clark, KB7QHC OK, good example. Cataracts presents absortion, transmission and reflection (they are whitish). To be analog I think should not have reflection. What do you think? (Perhaps seems maieutics but really I am trying to put my thoughts in order at first). What about the third point? I consider it important because light waves are in three dimensional space, so when they cancels in a region, reinforces in other and I can understand redistribution, but line travelling waves are in unidimensional space and here I can not visualize (realize?) the energy redistribution as in light interference. *Sorry, when I put interrogation words inside parentheses is that I am not sure the better/adecuated translation. 73 Miguel Ghezzi LU6ETJ Sorry I thought it was a very simple Cecil's answer. It was a joke, wasn't it?. It is my fault... I did not realize the signature and not translate well the paragraph :) Miguel |
#9
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On Fri, 28 May 2010 01:47:40 -0700 (PDT), lu6etj
wrote: On 28 mayo, 03:18, Richard Clark wrote: On Thu, 27 May 2010 19:10:41 -0700 (PDT), lu6etj wrote: 2) What would be Rs optical analog? Superman's cataracts with his xray vision. *This is probably going to be your only direct answer. 73's Richard Clark, KB7QHC OK, good example. Cataracts presents absortion, transmission and reflection (they are whitish). To be analog I think should not have reflection. What do you think? (Perhaps seems maieutics but really I am trying to put my thoughts in order at first). Whatever reflects, also absorbs and vice-versa. The notion that the interface is a singularity (infinitely thin) cannot be found in reality. Arguments that hinge on this non-existent property are made for the novice to intermediate student. Those who practice the science of optics at the bench never observe this metaphor in reality. What about the third point? I consider it important because light waves are in three dimensional space, so when they cancels in a region, reinforces in other and I can understand redistribution, but line travelling waves are in unidimensional space and here I can not visualize (realize?) the energy redistribution as in light interference. Sorry, when I put interrogation words inside parentheses is that I am not sure the better/adecuated translation. Superposition is the collapse of all possible solutions to a real one. To be real, we must have an observer. Frequently that is called a load. That load may be a transducer (light cell). Without the observer, both energies are present - nothing cancels. What is called redistribution is a superstitious necessity of trying to visualize the math. Redistribution is a strained term that is useful as a placebo, but nothing moves in the redistribution (an irony or a paradox which is more useful in entertainment). Traveling along the road of using optical metaphors is troubling for those who have never worked at an optic bench. Cut and paste theory from eminent authors occludes vision. 73's Richard Clark, KB7QHC |
#10
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On May 27, 9:10*pm, lu6etj wrote:
1) I did not think of (or is think on?) a laser source, I was one step before, I think only of a "coherent" source to match monofrequency simple AC generator analogy. Let's consider an *ideal* single-frequency laser to be a coherent monofrequency source for the purposes of discussion. 2) What would be Rs optical analog? I don't know enough about lasers to answer that question. In any case, I don't think reflections incident upon a laser encounter whatever Rs that might exist. I think we are going to have to settle for what happens outside of the laser which in important because what happens to photons in free space and other mediums cannot be hidden inside a transmission line. Standing waves of photons cannot stand still in a coaxial transmission line any better than they can stand still in free space. What some people are missing is that visible light waves and RF waves are exactly the same phenomena, just at a different frequency. The laws of physics governing light waves also govern RF waves. When someone says, "RF waves are different from light waves" or "RF waves can stand still", they are just showing their ignorance. They must also prove that reflected visible light waves in free space contain no energy and can stand still or else they are just blowing smoke. 3) Superposition is a medium phenomenon ¿yes?, for example "eter". Interference an result of it on a other "thing", for example photographic plate or screen. Are we agree? K No, in our context, superposition is the merging of two or more EM waves in any medium. If the waves are coherent, constructive/ destructive interference can occur. If partial or complete wave cancellation (permanent destructive interference) occurs, then the energy in the waves that existed before cancellation must be redistributed in another direction AND there are only two directions in an RF transmission line. I believe that Walter Maxwell defines any reversal in direction of reflected energy flow in a transmission line to be a "re-reflection". I prefer to call what happens to a single reflected wave a 1. "re- reflection" and what happens when two waves cancel a 2. "redistribution" of reflected energy. What about the third point? I consider it important because light waves are in three dimensional space, ... Let's compare coax with 0.2 square inches of cross-sectional area to a laser beam with 0.2 square inches of cross-sectional area. For the same power level, the power density, watts/in^2, will be the same - therefore the Poynting vectors will be the same. With such a concept in place, we can talk about a 100w RF source or a 100w laser source. -- 73, Cecil, w5dxp.com |
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