I think “window line” is less ambiguous for the stuff separated by plastic with squares cut out. I see “ladder line” being used to mean either window line or open wire line.
DX Engineering uses ladder line to mean the plastic dielectric line: https://www.dxengineering.com/search/part-type/ladder-line W7FG uses ladder line to mean 600 Ohm open wire line: http://trueladderline.com/w7fg-design-600-ohm-open-wire-feedline/ wunder K6WRU Walter Underwood CM87wj http://observer.wunderwood.org/ (my blog) > On Jan 7, 2019, at 8:39 AM, Don Wilhelm <donw...@embarqmail.com> wrote: > > There is a BIG difference between ladder line and open wire transmission line. > > Even low loss ladder line can have significant loss, especially when wet. > > Open wire feeders can truly be low loss even when operated at high SWR. > > So how do you construct proper open wire line? It is most easily done when > the 2 wires are under tension and spaced about 6 inches apart with as few > insulators between them as possible - the tension keeps the spacing > relatively constant - that is practical over a long horizontal run of the > transmission line. Then bring it up to the antenna feedpoint with wires > spaced apart with insulators, and likewise on the run to the house entry or > better yet to the shack - the more insulators, the greater the loss can be. > You can use ladder-line from there into the shack, or you can put a good > current mode balun at the house entry and from there run a short length of > coax to the tuner. > > As I have mentioned before, whether a 1:1 balun or a 4:1 balun will work > better has to be determined - it depends on the feedline length, the > frequency, and the feedpoint impedance of the radiator for that particular > frequency. If the feedpoint impedance at the tuner end of the feedline is > already low, a 4:1 balun will make it 4 times lower and difficult for your > tuner to deal with. > > A G5RV antenna on 160 meters will not be very efficient (the high current > point will be somewhere down the transmission line and not at the center of > the antenna). One thing is true, the RF voltage at the ends of the antenna > is the highest, and the highest current is 1/4 wavelength away from the end, > even if that is at a point well down the feedline. The equal and opposite > currents on the feedline will cancle making that highest current point not > useful for radiating a signal. > > Radiator lengths greater than 1/2 wavelength can be efficient, but shorter > than 1/2 wavelength will be less efficient because the balanced currents on > the feedline cancel each other out. That is just plain physics. > > 73, > Don W3FPR > > > > On 1/7/2019 10:49 AM, Wes Stewart wrote: >> Try running that 102' long "G5RV" up 50' on 160 meters. Feed it with 100' >> of Wireman 553 "low loss" ladderline. The 0.1 dB matched loss turns into >> over 13 db at the input and that's without considering tuner loss. (Source: >> EZNEC and TLDetails) > ______________________________________________________________ > 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 > Message delivered to wun...@wunderwood.org ______________________________________________________________ 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 Message delivered to arch...@mail-archive.com
