wrote:
As gain increases with a yagi design the forward
lobe narrows. So to the gurus of this group, what
actualy creates the narrowing of the forward lobes ?
______________________

A good analogy that needs no math to understand is that of squeezing an
inflated balloon from its normally spherical shape into whatever shape is
more appropriate for the application. There is a given volume of air in
that balloon. If you want the surface of the balloon to extend further from
the origin of its original sphere, the new shape must be narrower in one or
more planes than the original shape.

The shape changes can come from squeezing the balloon (pattern)
horizontally, vertically, or in combination -- which, in antenna hardware is
accomplished by an appropriate array of, and feed system for, its radiating
elements.

RF