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Reg Edwards wrote: Yet another reason why the so-called swr meter does not measure swr is because there is no transmission line (between meter and transmitter) on which to measure it. SWR on it cannot not exist. The consensus of opinion over on science.physics.electromag is that a two foot long section of 50 ohm coax is all the length needed to force the V/I ratio to be 50 ohms at HF - something to do with the length Vs separation between conductors ratio. That V/I ratio = 50 is the assumption made by the SWR meter designer when the meter is calibrated. -- 73, Cecil ==================================== Cec, I've never before heard such a loony notion. Your science.physics.elecromag correspondent invented the idea specially for you and was amusing himself by pulling your leg. And now you're trying to pull mine. --- Reg, G4FGQ |
#2
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Reg Edwards wrote:
W5DXP wrote: The consensus of opinion over on science.physics.electromag is that a two foot long section of 50 ohm coax is all the length needed to force the V/I ratio to be 50 ohms at HF - something to do with the length Vs separation between conductors ratio. That V/I ratio = 50 is the assumption made by the SWR meter designer when the meter is calibrated. Your science.physics.elecromag correspondent invented the idea specially for you and was amusing himself by pulling your leg. And now you're trying to pull mine. OK, Reg, when the conductors are 1/4 inch apart, what length of coax is necessary for the Z0 of the coax to effect the ratio of E-field to H-field? Those pretty smart guys over on s.p.e say a ratio of 100:1 length/separation is plenty enough to force the V/I ratio to be 50 ohms. We can actually measure the V/I ratio at the input to the SWR meter. I'll bet, when a properly calibrated 50 ohm SWR meter is reading zero reflected power, that the V/I ratio is indeed 50 ohms. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
#3
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Reg,
I'm afraid you're wasting your time trying to convince mere amateurs with your carefully reasoned and flawless logic. Instead, I suggest you concentrate your efforts on the true professionals out there. Surely, they'll immediately see the wisdom of your arguments and change their careless ways. I'm talking of course about the engineers in such unenlightened companies as HP/Agilent, Narda, Tektronix, Wiltron/Anritsu, and their colleagues and competitors in the U.K. They're constantly making the same egregious error, by specifying the SWR of terminating resistors, connectors, test equipment device inputs, and even (gasp) outputs. Once the professionals change their ways, amateurs, copycats as they are, will surely follow. Good luck with your quest! Roy Lewallen, W7EL |
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