Open wire line changes a bit in wet weather due to moisture on the insulation between the wires. The worst is the type with a continuous web of insulation that was commonly used for television lead-in before coax came into common use. Next best is "window" line what is the same basic insulation, but wider spacing (and a higher impedance) with openings - windows - cut in the insulation to make it more like "air" dielectric line. The best is true open wire line which seems to be what you are referring to. With good insulators, it is virtually unaffected by moisture unless you dunk it in salt water. I've used both the commercial type with (polystyrene?) insulators and home brew stuff I made up using ceramic insulators.
At my last QTH I had an "inverted V" doublet fed with open wire line. The center support was a wooden pole, so I made up the feed line using common "dog bone" end insulators. The insulators were mounted on the support pole using screw-eye standoffs. I got a bunch of the cheap screw eyes with the little insulator in the center made for use with TV "twinlead" and popped the little insulator out. The eye is soft metal that is easily bent, so I opened it up to slip it around the center of each 'dog bone' insulator then clamped it down with pliers. Ribs on the insulator kept the eye centered. Screwed them into the pole at about 3 foot intervals and then strung some #14 copper wire through the ends to make up the feeder. Kept the wire under a little tension with a few small ty-wraps to secure it. A bit of wire wrapped around the main conductor and running outside the hole would so as well. With a white pole, white "dog bone" insulators and using white insulated wire, the whole installation was very tidy and the feeder virtually invisible. I never noticed any significant change in tuning requirements (used an external manual tuner) on any band when it was dry, in the middle of a typical Oregon "gully-washer" downpour or when it was coated in ice. Ron AC7AC -----Original Message----- Sorry for an off-topic question. Does anyone have any information about the dry vs wet characteristics of "450 ohm" ladder line? I have never used this type of line, but I might have to use it for "mechanical" reasons to feed another antenna now being built. I am told that its characteristics change when wet from rain, but which characteristics change and by how much at HF. A remote ATU to compensate is not to be used with this particular antenna / feeder. Any comment would be appreciated. 73, Geoff GM4ESD ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
