On 9/29/2012 9:12 PM, Robert G. Strickland wrote: > What I'm curious about is whether some such device, at the feed point of a > doublet, > in turn fed by window line is of any use [assuming an appropriate tuner at > the radio > end of the line]. You have said, accurately so, that a current choke at the > feed > point of a dipole [let's leave off-center fed antennas out of it at this > point], in > turn fed by coax,
In all of this discussion, I have not used the word "coax." You have read that somewhere else. > keeps RF from flowing on the outside of the coax and subsequently > becoming "part of the antenna" and in turn picking up noise/etc. Another way > of > phrasing my question is, does the coax situation apply to open feeders, also? YES! That is EXACTLY what I have repeated, over and over again. It has NOTHING to do with coax. Coax, if it is not decoupled by a common mode choke, simply ADDS to the imbalance that is already present. EVERY transmission line needs a common mode choe at the feedpoint to decouple the line. Off-center fed antennas, like the so-called "Windom" in all of its variations, are WILDLY unbalanced. As a result, they are notorious for being NOISY, for putting RF in the shack, and for toasting common mode chokes. It is a complete fiction to feed with with parallel wire line and CALL it balanced, and decide that it needs a balanced tuner! The antenna is unbalanced, so the feedline is unbalanced, and a balanced tuner does nothing except transfer dollars between the purchaser and the seller. In the old days, when RFI did not exist (few of us are old enough not to remember TVI in the 50s), the Windom MIGHT have been a good idea. Today, with RF noise sources everywhere and home stereo rigs full of Pin One Problems ready to bring RF into equipment and detect it, Windom antennas are a really bad idea. 73, Jim Brown K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
