In a message dated 10/13/07 4:58:04 PM Eastern Daylight Time, [EMAIL PROTECTED] writes:
> There is no difference if the balun is on the input or output side of an > unbalanced tuner. In theory, no. In practice, there can be a big difference. See > > > < > http://fermi.la.asu.edu/w9cf/articles/balun/balun.html#SECTION00050000000000000000> > > He's not looking at the big picture. If the balun is ideal, or close enough to ideal, or if the shack-end impedance of the balanced load are within a certain range, the unbalanced-tuner-with-balun-at-the-antenna-end idea works fine. Thousands of hams use it with no problems and good results. But in some cases the shack-end impedance of the balanced line can be very high, very low, and/or highly reactive. Under those conditions some baluns don't work well, and all sorts of odd things happen. Sometimes the end result works well enough that the ham doesn't notice anything wrong, particularly if s/he has nothing else for comparison. Sometimes the problems can be fixed by things like changes to the line length or adding reactive elements in parallel or series with the line. You can't just blindly increase the number of turns on a wound-core balun to increase the impedance because you may set up self-resonances that cause all kinds of fun. The best approach IMHO is to model the antenna-feedline system and see what the actual shack-end impedances are. Or measure them. Then decide what tuner setup is needed to do the matching job. 73 de Jim, N2EY ************************************** See what's new at http://www.aol.com _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
