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## Large Wire Yagi Structures

 To: Large Wire Yagi Structures aa6eg@tmx.com (Pat Barthelow) Tue, 31 Dec 1996 17:10:30 -0800 (PST)
 ```Wire Yagi Experts? We at Marina Ca, (N6IJ Club Station) have a large converted MARS radio station site which provides a opportunity to build a large wire yagi array, possibly on 2 bands, (40 meters, 7 elements, 20 meters, 10 to 15 elements) pointed to Europe. There exist 4 wooden poles, 65 feet high, forming a rectangle 72 feet wide, by 350 feet long. If we guy them, and connect the poles with a structural member (probably 5/16" ehs strand) from the power company which is already available, we are contemplating supporting the 2 large yagi arrays. A number of questions need to be answered before proceeding..... and we are looking for some outside input. 1. Will a grounded steel strand, structural member in the vicinity of, but separated by approximately 20 feet from the tips of the wire yagi (20 meter) elements, adversely affect the performance of the yagi? By how much? (In the case of 40 meters the distance between the tips of the 40 meter yagi, and the continuous strand will closer, about 5-10 feet. 2. Can we place a 20 meter yagi (possibly 8 to 12 elements) in front of, and collinear with the "boom" of the 40 meter yagi with relatively small separation without adversely affecting either's performance? 3. The poles' long axis points to Europe (N 30 deg E), but they are on a slight vertical incline, about 5 degrees uphill slope to Europe. (Southwesterly ground elevation is 150 ft. MSL, and Northeasterly ground end is 180 ft. MSL, in 350 foot span, a 30 foot rise in a 350 foot run. The yagi arrays, would be more or less parallel to the ground below them, making a "boom" angle of 5 degrees, to the horizontal. At the director (Northerly) end, there is a flat plateau hilltop that the whole antenna would illuminate, even the lower (reflector) end. The arrays would be about 55 to 60 ft above ground. Would the up-tilt of the boom add terribly to the vertical angle of radiation of the array, compaed to a flat, level, yagi array? 4. Are there bandwidth problems with wire yagis, being that the wire diameter is quite smaller than more typical, aluminum tubing elements? We will use #10 Copperweld. Any way to have an acceptable match on both phone and CW ends of 20 and 40 meters? 5. I have a detailed land countour map, with pole locations, that could be used for a terrain-yagi model. Anyone interested in modelling this? 6. If/when we complete this monster, we would like to invite contesters/DXers to visit and use the station, already equipped with KW rigs, 6-30mHz Log Periodics, and a Discone (80 - 10 meters). Contact me if you want to come down to operate, or help construct these yagis.... 7. Is it manageable/sensible to create such a large wire yagi array? What are the problems? If you have EXPERIENCE in WIRE yagis, please advise. The poles are sturdy, in good shape, class 2, 70 foot poles, buried in the solid sandy ground about 9 feet, and will be guyed. We may need a stuctural engineer to alalyze the forces involved in this wire yagi array. 73, DX, de Pat, aa6eg@tmx.com AA6EG; Trustee for N6IJ. Marina CA. -- FAQ on WWW: http://www.contesting.com/towertalkfaq.html Submissions: towertalk@contesting.com Administrative requests: towertalk-REQUEST@contesting.com Problems: K7LXC@contesting.com Sponsored by Akorn Access, Inc & KM9P ```
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