Array Solutions Four Square Controller
9
www.arraysolutions.com
Array Solutions
Ofc: 972 203 2008
350 Gloria Rd.
Fax: 972 203 8811
Sunnyvale, TX 75182
Theory of operation:
The system consists of four verticals in a square separated by .25 WL (= side of the square)
Quadrature
Feeding
The Array Solutions controller can be used to feed all 4 of these verticals in such a way as to
accomplish a
quadrature
feed to each antenna.
Quadrature
means fed in 90 degree steps and
with equal drive and current magnitude.
The “rear” element in our diagram above is the one on the closest to us on the axis. It is fed with
1A of current at 0 degrees, the next two elements are diagonally positioned and are fed in phase
with 1A of current at -90 degrees, and finally the “front” element is fed with 1A of current at -180
degrees. The direction of firing is through the diagonal of the 4-square towards the element fed
with -90 degrees current. The array has a forward gain of 5.5 dB over a single vertical.
Note the following diagrams are normalized to 5.5 dB of gain over a single same-type
vertical. Do not confuse 5.5 dBi with real gain, which can be more with full-size quarter-
wave verticals and good ground properties. This is to display the gain over a same type
vertical - ignore the dBi notation and consider it as a dB reference over single vertical.
The take-off angle in this system with this mediocre ground is 23 degrees. But with an excellent
ground radial system and better ground conditions it is possible to lower the angle.
The feed method using an L-network to achieve the required
90 degrees
phase shift was
developed by Lewallen, and we refer to it (as in ON4UN’s book) as the Lewallen feed method.
Optimized Feeding
This is probably why you purchased this unit.
Using a phase shift greater than 90 degrees (back element to center elements) and greater than
180 degrees (back element to front element) makes it possible to improve the performance of the
4-square. We developed a system where the phase delay can be adjusted to achieve 90 to 120
degrees (for the center elements) or 180 to 240 degrees (to the front element).
Unlike the hybrid coupler technique where the phase shifts are required to be quadrature (in
90 degree steps and equal current magnitudes) by nature of the concept, our “optimized feed
system” allows the user to optimize the drive current phase shifts and magnitudes since it is
accomplished with variable networks plus (in most cases) a 180 degree phasing line.
Robye Lahlum has developed the mathematics which are published in detail in ON4UN’s book
Low Band DX-ing, edition 4 (an ARRL publication, available June 2005). The systems and the
mathematics make it possible to have absolute control of the exact phase and magnitudes of the
feed currents to each element. Networks can be designed that achieve feed current phase angles
and magnitudes as desired. We are no longer bound to equal current magnitude in each element
and 90 degree phase increments.
Our “optimized feed system” uses a phase shift of -111 degrees to the center elements and -224
degrees to the front element. As explained above the -111 degrees delay is achieved by a simple
L network and the -224 deg. phase sift to the front element is achieved through a 180 deg line,
with, in addition, an L network taking care of the remaining (224-180=) 44 degrees.
