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"Dr. Slick" wrote in message m... Cecil Moore wrote in message ... Dr. Slick wrote: If you agree that the Pref/Pfwd ratio cannot be greater than 1 for a passive network, then neither can the [Vref/Vfwd]= rho be greater than 1 either. Sqrt(Pref/Pfwd) cannot be greater than one. (Z2-Z1)/(Z2+Z1) can be greater than one. Both are defined as 'rho' but they are not always equal. (Z2-Z1)/(Z2+Z1) is a physical reflection coefficient. Sqrt(Pref/Pfwd) is an image reflection coefficient. I agree that Sqrt(Pref/Pfwd) cannot be greater than one for a passive network. (Z2-Z1)/(Z2+Z1) can be greater than one, for passive networks and certain combinations of complex Z1 and Z2. I feel this is incorrect usage of this formula, which should be limited to purely real Zo. A [rho] that is greater than one gives meaningless negative SWR data, and is limited to active devices. it only gives negative swr values if you incorrectly use the lossless line approximation to calculate vswr from rho. that is the incorrectly applied formula in this case. that formula is not valid for a lossy line, you must go back to the original definition of VSWR=|Vmax|/|Vmin|. which as we have also noted is not meaningful on a lossy line as Vmax and Vmin are different at each max and min point because of the losses in the line affecting both the forward and reverse waves. |
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