Q. What is the optimum antenna type to give the maximum gain given a
fixed overall length of elements? Or, alternately, what's the minimum
amount of wire/tubing to give a specified gain? (Neglecting support
structures)
As an example, for a gain of 15 dBi, an 11 element Yagi appears to have
about the same gain as two stacked 6 element Yagis which collectively
use one more element. But what about collinears, V Beams, arrays of
different sized Yagis etc. etc.?
Just out of curiosity.

Alan