On Thu, 17 Sep 2009 19:15:56 +0200, Szczepan Bia?ek
wrote:

If antenna has only one source it is omnidirectional. If two or more is
directional because the waves from different sources interfere.

The halve wave dipole has the two sources. The next two appear than a
dipole is longer than the wave length.
So that what R. Clark wrote is obvious: "[* What is this proportional and
proportionate mean? For a dipole of
0.05 WL to a dipole of 0.5WL, the far field change for that 10:1
variation is negligible. However, for a dipole of 0.5WL to a dipole
of 1.25WL, the far field change for that 2.5:1 (a smaller proportion)
variation is very noticeable.]

In the space of two sentences you contradict yourself. You don't get
it, do you?

73's
Richard Clark, KB7QHC