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[TowerTalk] 1/4 wave 160

 To: [TowerTalk] 1/4 wave 160 n4kg@juno.com (n4kg@juno.com) Tue, 5 Feb 2002 19:17:38 -0600
 ```On Tue, 5 Feb 2002 "Sain'T Tom" writes: > > Anybody got any REAL WORLD and WORKING height dimensions > of a 160 meter quarter wave vertical made of Rohn 25? > > Thanks > Tom K4RV > The ARRL Antenna Books (and Handbooks?) have a graph showing % of freespace length vs. L/D ratio of the 1/2 WL wire (or element). I believe someone indicated that Rohn 25 could be modeled as a cylinder of 8 or 9 inches diameter, OR, you could model it as 3 cylinders of 1-1/4 inch diameter in a triangle 11-1/4 inches center to center with the ends connected. I assume you are not planning for any other antennas on the tower / vertical. If you are going to shunt feed it, anything close will work. Tom N4KG OK, here are the numbers... Speed of light = 300,000,000 meters / sec = 984,000,000 ft/sec Frequency = 1,800,000 cycles / sec 1/2 WL = ( 984,000,000 / 2 ) / 1,800,000 = 273.3 ft Length / Diameter ratio for 1/2 WL = 273.3 / ~0.7 = 390 "K Factor" for L/D ratio of 400 ~= 0.97 1/2 WL at 8.5 inches OD = 273.3 X 0.97 = 265 ft 1/4 WL = 132.5 ft ________________________________________________________________ GET INTERNET ACCESS FROM JUNO! Juno offers FREE or PREMIUM Internet access for less! Join Juno today! For your FREE software, visit: http://dl.www.juno.com/get/web/. ________________________________________________________________________ Where do you get ICE bandpass filters & beverage matching boxes? The same place that pays for the hosting of this list: The eHam Store. Order online at http://store.eham.net. ----------------------------------------------------------------------- ----- FAQ on WWW: http://www.contesting.com/FAQ/towertalk Submissions: towertalk@contesting.com Administrative requests: towertalk-REQUEST@contesting.com Problems: owner-towertalk@contesting.com ```
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