On Nov 4, 2009, at 5:05 PM, Steve Ellington wrote: > It's called a transmission line transformer and is very common.
Yes, we all know about them. Just walk 180 degrees on a constant SWR circle on the Smith Chart, with the transmission line impedance at the center of the Smith Chart (or use 1/4 wavelength in the Telegrapher's Equation). But this is what you'd stated (I am not changing a single word): > 4. Example: A full wave dipole center fed with 50 ohm coax. You can use a 600 ohm transmission line to transform a high impedance to get a reasonably close match to 50 ohms because the impedance at the center of that dipole is *not* infinite but some large number (W8JI has good estimates in the Zepp article on his web site). But you cannot transform anything other than a 50 ohm feed point into a 50 ohm termination by using a 50 ohm transmission line. (Unless the line is infinitely lossy.) It should be obvious from the Smith Chart -- constant SWR circles won't hit 50+j0 unless the SWR circle itself has 0 radius (i.e., SWR = 1.0:1) 73 Chen, W7AY ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
