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

Francesco L. wrote:
I'm assembling a switch box for a 2 element vertical phased array. My idea
is to create a system able to generate two alternate (and switchable)
cardioids using a delay line (90°, 1/4 wavelength) and a two ways, two
position relay in order to cover with an agle of 120° degrees one direction
(e.g. North) or the other. As you all know, if two elements are fed in
perfect phase the radiation pattern obtained is called broadside. This is
exactly what I want to obtain introducing a second relay in order to get a
third direction. At this point my question is: should I put a 10 w 100 ohm
resistance (non inductive) between the two antennas (it's called Wilkinson
power divider or power splitter) or the system works perfectly that way?
There are two different school of thought: the first consider the wilkinson
a must, since it lowers the swr and keeps it under control, the second
school thinks it burns useful power and does not transfer all power.
So what's your point of view?
Thanks a lot in advance for your contribute
Francesco ik8vwa