Roy Lewallen wrote:
I highly recommend reading the "Phased Array Techniqes" part of Chapter
8 of any edition of the _ARRL Antenna Book_ for about the past 15 or 20
years. It was first written not long after Dana Atchley popularized the
use of the Wilkinson Divider for feeding phased arrays (and the error of
which he later saw), so it contained quite a bit of detail about why
that's a bad idea. When I re-wrote the section for the recent 21st
Edition, I reduced the amount of material regarding the Wilkinson
divider, since I thought it had finally faded away. I'm disappointed to
hear that there's still a "school of thought" which regards it as a
viable feed system after all these years.

If you have the 21st Edition, you'll find the complete text of the
earlier material on the included CD. It contains more detail about why
the Wilkinson divider isn't appropriate for this application.

Devoldere's _Low Band DXing_ also contains a lot of good information
about phased array feed systems.

Roy Lewallen, W7EL


Probably because a lot of folks don't realize that the power isn't
divided equally among elements in most ham phased arrays. A lot of the
textbook examples are for microwave applications (e.g. radar) where they
do assume equal powers to each element, but that's where the array is
specifically designed to present 50 ohm resistive feedpoint impedances
at all ports, regardless of phasing, especially if it's an active array
with amplifiers at each T/R module.

There's also plenty of examples out there for microwave broadside arrays
of many identical elements at uniform spacing 1/2 wavelength, for which
a equal power divider actually works fairly well. (or, at least, it's
easy to analyze)