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Zo and Ro
Not having much else to do at present I thought I would make a comment on Zo and Ro of transmission lines. For entertainment and educational value, of course, if you like that sort of thing. The condition for which Zo of a transmission line is always purely resistive (Zo = Ro) is extremely simple. It is - G = C * R / L where G is shunt conductance, C is shunt capacitance, R is series resistance, L is series inductance, all per unit length of line. Which applies to any line length, at any frequency from DC to UHF. It is a shortcoming of the Smith Chart, with Zo always equal to Ro, that it does not make you aware of this and can lead you up the garden path if you are not careful. As has recently occurred on this newsgroup. Don't get me wrong. I'm not against Smith Charts. They are graphically educational within their limitations. ---- Reg, G4FGQ |