[TowerTalk] Stacking Distance for Multiple Yagis

[Bob Gates]

Morning all,

Would appreciate your opinions on the "optimal" vertical spacing when stacking two 10-20M tribanders on a tower.  Obviously there needs to be some tradeoffs.  I've read everything I could find on the subject, and it appears a majority use a 30'-35' spacing, although I've seen examples using up to 50'.  For the latter, can anyone explain how this much separation was calculated?  

Also, when stacking two monoband yagis, a half wavelength separation appears to be the optimum.  But, if necessary, how much can you shorten that distance without measurable degradation in performance?  Again, I've also seen examples of roughly 3/4 wavelength separation, and can't figure out why. 

All replies appreciated, but, please, no flames.  I'm still recovering from the comments on my idea to raise a 120' tower with a gin pole, and my confidence level is at the danger point.  My shrink says I should avoid all controversial brainstorming for the forseeable future until I recover.

Thanks in advance,

73, Bob W7BJ