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The Four Square System Phasing Unit should be mounted as shown in
Figure 2
with cover upward
and the control and coaxial cable connections downward to prevent water from entering the box.
The stainless steel base of the Four Square System Controller has weep holes to allow condensation
that may build up inside the unit to leave.
In normal operation, the Four Square System Phasing Unit will present a reasonably good 50 Ω load
even if the elements are slightly out of tune. The typical operating SWR with normal antennas will
be less than 1.3:1. If there is a problem with one or more elements or feed systems in the array,
there will be an increase in dummy load power. The increase in dummy load power is often greater
than the increase in array SWR. Although not generally necessary, there can be some advantage in
monitoring the array with a power/watt meter and dummy load located at the operator's station if
element or feedline reliability is suspect.
Copper Straps Connected
System Controller Mounted
to Mounting Pipe to Mounting Pipe
Figure 2
The “dump” dummy load can be located near the center of the array through a 50 Ω coaxial cable.
Placing the dummy load near the operating position allows monitoring of dump power, or use of the
load for other applications.
The 50 Ω dummy load is an integral part of this four square system. Power is divided between the
four vertical antennas in a modified hybrid phasing scheme. Even when properly operating, some
power is 'dumped'. In normal operation at legal limit, dump power can be as high as 150 watts. This
is normal, and it occurs because mutually coupled elements do NOT have equal impedances, nor are
they 50 Ω pure resistances. Dumped power levels beyond 10% of transmitted forward power
generally mean the system has a problem, such as elements being out of tune or transmission line
problems in the array.
Antenna Feedline
Four Square System Phasing Unit to the Vertical Antennas:
The weakest link in an antenna
system is often the coaxial cable connections. All connections must be high quality and weather
tight to prevent contamination and corrosion, which can cause the feedline impedance to change and
loss to increase. This can affect the signal-to-noise ratio and the directivity of the array. Do not
splice the feedlines in the array. The vertical antenna feedlines from the Four Square Phasing Unit,