"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.)" Don't worry....It will be!
Steve N4LQ [email protected] ----- Original Message ----- From: "Kok Chen" <[email protected]> To: "Steve Ellington" <[email protected]> Cc: "Elecraft Reflector" <[email protected]> Sent: Wednesday, November 04, 2009 8:51 PM Subject: Re: [Elecraft] K3 SWR Accuracy - reprise > > 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 > > -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.698 / Virus Database: 270.14.50/2481 - Release Date: 11/04/09 14:51:00 ______________________________________________________________ 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
