a parabolic reflector fed with a feedhorn. no 'elements', just a hole in a
pipe and a big curved plate. you need to define the parameters a bit more.
for instance with no reflectors or directors, just driven verticals you can
make lots of gain. phased array radars have no wire/tubing elements, just
holes in a plate each with its own transmitter/receiver. and how do you
count dishes, corner reflectors, and the ground? by changing the height of
an antenna you can drastically change the gain at some particular takeoff
angle, so maybe you want to restrict it to free space. an do you want
minimum element count, or total material length? a very long wire can
create high gain lobes, but may not be very useful if you are thinking of
something rotateable.

"Alan Peake" wrote in message
...
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