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![]() "Hal Rosser" wrote in message ... I think he was correct about the half-wave length of feedline: according to the ARRL Antenna Book - 17th edition copyright 1994 - page 24-12 in chapter 24, under the Heading "Special Cases" and under the sub-heading "The Half-WaveLength Line", it pretty clearly states that regardless of z, it will be the same on both ends of a half-wave line. and sections having such length can be added or removed without changing the load Z. (as long as loss is negligible) Also - You don't need to know the VF if you use a dip meter (or MFJ 259) - And he would want the length to be half-wave so as to be able to ignore the characteristic impedence of the zip line and deal directly with the impedence of the dipole directly. Exactly I also have a W6RCA type antenna up...80m dipole in the trees 25-50 feet, fed by 98 feet of homemade 4" spaced ladder line, and ending outside the shack wall with a way to add-in lengths of the feed line by 1 foot, 2 foot, 4 feet or 8 feet. This allows tuning the feedline onto any ham band almost via harmonic relationship of the bands . You endup with a multiple halfwave feedline and whatever swr the antenna runs shows up at the feedpoint (50 ferrite coax to ladder balun 1:1). Best antenna I have. Always better to tune the feedline, and translate the antenna characteristic from the remote locale to the shack wall. There is some loss I guess, but I cant detect it or measure it, and I dont care because the antenna radiates and receives and I get 59 reports. Tim |
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