Steve AA8AF wrote: Alan Chester (G3CCB)(SK) proposed a solution for the high end impedance of a 1/2 wave antenna. Mr. Chester rationalized that there might be some impedance-friendly length of wire usable for an end-fed antenna that didn't present the tough-to-tune, high-impedance load on a select set of bands. ...
-------------------------- One way to look at it is that if the end-fed wire is longer than a 1/2 wave antenna, the extra length is simply a single-wire feedline. Of course, the 'feeder' will also radiate UNLESS one manages to match the impedance of that wire (roughly 600 ohms for a typical wire) to the feed point impedance. To do that, you move the feed point for the single wire away from the high impedance at the end and toward the lower impedance (73 ohms in free space) that will be found near the center. At some point that wire will see a good match and it will have no standing waves. No standing waves on even a signal unshielded wire means it won't radiate (ya' gotta have standing waves to make electromagnetic fields). Of course, exactly that was done by the famous Loren G. Windom (8GZ/W8GZ) and is known today as a Windom antenna. That's the REAL Windom, not the modern variations using open wire feeders that are really just off-center-fed doublets. Windom's antenna used a single wire feeder that did not radiate significantly, but it only worked properly at the one frequency at which the feed line was matched to the antenna. Ron AC7AC _______________________________________________ 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
