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## [TowerTalk] ANTENNA SURFACE AREA VS ROTOR

 To: [TowerTalk] ANTENNA SURFACE AREA VS ROTOR NI6W@yagistress.minden.nv.us (Kurt Andress) Tue, 16 Jun 1998 23:44:53 -0700
 ``` > Subject: [TowerTalk] ANTENNA SURFACE AREA VS ROTOR To: > Date: Tuesday, June 16, 1998 12:36 PM > > Last question is, would anyone care to guess what the surface area > would be for a 15M 6 element monobander on a 38 ft boom would be. > Estimates are OK. > TNX & 73 Denis, W4DC Denis, I get a different area than the one cited by KJ6Y for the KLM 615 36' 3" boom. If the boom is 3" dia by 36' the effective area is 6.5 SqFt. If the boom is 2" dia (as in my KLM manual) the area is 4.5 Sq Ft. The effective area of the 6 KLM elements is 3.6 Sqft. The reason the antenna area in the KLM data is overstated is due to the erroneous methods used. KLM is not alone in making this mistake. 6 years ago the "conventional wisdom" said that one should combine element and boom areas according to the Pythagoreum theory to obtain a net effective area (if you payed attention in Trig class it uses the A^2 = B^2 + C^2 formula). This has since been proven wrong. The maximum effective area of any antenna is simply the largest of either the elements or the boom. If your 38' long boom is 2" Dia constant, the effective area is 4.22 SqFt. If the Dia is 3", the effective area is 6.33 SqFt. This assumes that the antenna you describe uses small elements, like the KLM that are only 3.6 SqFt. If your antenna uses big fat elements, then you need to determine if they have a larger effective area than the boom. 73, Kurt YagiStress - The Ultimate Mechanical Design Software for Yagi's Visit - http://freeyellow.com/members3/yagistress -- FAQ on WWW: http://www.contesting.com/towertalkfaq.html Submissions: towertalk@contesting.com Administrative requests: towertalk-REQUEST@contesting.com Problems: owner-towertalk@contesting.com Search: http://www.contesting.com/km9p/search.htm ```
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