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## [TowerTalk] Optimum Stacking Distance

 To: [TowerTalk] Optimum Stacking Distance jirka@jimaz.cz (Jiri Sanda) Fri, 27 Jul 2001 23:40:32 +0200
 ```Hi, Tom of course theoretically you are right but in the real life and real practical situations the longer boom you have the wider spacing for maximum gain is needed. (OK various nulls and lobes are comming but....). The discussion - if I understand it well goes for Yagis 0.5 - 1.5 WL ! 73 ! Jiri OK1RI -----Original Message----- From: owner-towertalk@contesting.com [mailto:owner-towertalk@contesting.com]On Behalf Of Tom Rauch Sent: Friday, July 27, 2001 11:17 PM To: Robert Shohet; towertalk@contesting.com; Bill Hider Subject: RE: [TowerTalk] Optimum Stacking Distance Bill sure has it right. We should always model the antennas to pick stacking distance! We used to do this on paper before it was common to use personal computers to model antennas. You can do something like this: 1.) You look at the pattern of one antenna by itself. 2.) You look at the pattern of two non-directional radiators with the same polarization spaced various distances apart. 3.) You either adjust distance between the two non-directional radiators so the pattern they make causes a null where the real antenna has a major lobe that you do not want (minimum sidelobe stacking), or you adjust the distance so the stacking of the two non-directional radiators shows a null area extending about half- way up the main lobe (maximum gain distance) of what would be the pattern of a real antenna. So you see, stacking distance has absolutely nothing to do with boom length! Optimum stacking distance is a function of how narrow the original pattern is....or where the minor lobes are that you want to get rid of. Rules of thumb do not work. Take two freespace dipoles for example. The boom length is zero. Optimum gain stacking distance is just barely under 3/4 wavelength, because that forces four deep nulls in the main lobe, removing the most possible energy from unwanted directions. Zero boom length = 3/4wl stacking distance!!! Make it two two element yagi's in freespace, and optimum gain stacking distance is slightly wider than the dipoles no matter how long the booms of each yagi are. Make it two antennas of any type that have 20 degree beamwidth, and stacking distance has to be so wide that it forces a null over a good part of the main lobe...otherwise you don't get maximum gain. Stacking distance would be well over 1-wl no matter how long the booms are. Stacking distance relates only to how wide the individual antenna patterns are (over earth), and if you want high gain or good side lobe suppression (you can't normally get both). The narrower each antennas pattern, the wider stacking distance becomes. It has nothing at all to do with boom length. 73, Tom W8JI W8JI@contesting.com ----- FAQ on WWW: http://www.contesting.com/FAQ/towertalk Submissions: towertalk@contesting.com Administrative requests: towertalk-REQUEST@contesting.com Problems: owner-towertalk@contesting.com ----- 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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