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"Dr. Slick" wrote in message om... As Reg points out about the "normal" equation: "Dear Dr Slick, it's very easy. Take a real, long telephone line with Zo = 300 - j250 ohms at 1000 Hz. (then use ZL=10+j250) Magnitude of Reflection Coefficient of the load, ZL, relative to line impedance = ( ZL - Zo ) / ( ZL + Zo ) = 1.865 which exceeds unity, and has an angle of -59.9 degrees. The resulting standing waves may also be calculated. Are you happy now ?" --- Reg, G4FGQ Well, I was certainly NOT happy at this revelation, and researched it until i understood why the normal equation could incorrectly give a R.C.1 for a passive network (impossible). According to Adler, Chu, and Fano, "Electromagnetic Energy Transmission and Radiatin", John Wiley, 1960, (60-10305), when they talk about lossy lines, and say that Zo is complex in the general case, they come up with a maximum value for the reflection coefficient of (1 + SQRT(2)). Eq 5.14b. Remember, it is a lossy line; so, the reflected voltage gets smaller as you move away from the load. Somebody might want to check this out, in case I misunderstood something. BTW, the three authors were all MIT profs. Tam/WB2TT |
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The problem is in leaping to the conclusion that a reflection
coefficient greater than one means that more energy is coming back from the reflection point than is incident on it. It's an easy conclusion to reach if your math skills are inadequate to do a numerical analysis showing the actual power or energy involved, or if you have certain misconceptions about the meaning of "forward power" and "reverse power". But it's an incorrect conclusion. Then, having come to the wrong conclusion, the search is on for ways to modify the reflection coefficient formula so that a reflection coefficient greater than one can't happen and thereby disturb the incorrect view of energy movement. It's simply an example of faulty logic combined with an inability to do the math. Adler, Chu, and Fano do understand the law of conservation of energy, and they are able to do the math. Roy Lewallen, W7EL Tarmo Tammaru wrote: "Dr. Slick" wrote in message om... As Reg points out about the "normal" equation: "Dear Dr Slick, it's very easy. Take a real, long telephone line with Zo = 300 - j250 ohms at 1000 Hz. (then use ZL=10+j250) Magnitude of Reflection Coefficient of the load, ZL, relative to line impedance = ( ZL - Zo ) / ( ZL + Zo ) = 1.865 which exceeds unity, and has an angle of -59.9 degrees. The resulting standing waves may also be calculated. Are you happy now ?" --- Reg, G4FGQ Well, I was certainly NOT happy at this revelation, and researched it until i understood why the normal equation could incorrectly give a R.C.1 for a passive network (impossible). According to Adler, Chu, and Fano, "Electromagnetic Energy Transmission and Radiatin", John Wiley, 1960, (60-10305), when they talk about lossy lines, and say that Zo is complex in the general case, they come up with a maximum value for the reflection coefficient of (1 + SQRT(2)). Eq 5.14b. Remember, it is a lossy line; so, the reflected voltage gets smaller as you move away from the load. Somebody might want to check this out, in case I misunderstood something. BTW, the three authors were all MIT profs. Tam/WB2TT |
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