In principle, the Shared Apex Loop Array provides directivity by summing signals from one loop with delayed signals from an oppositely phased and positioned loop. Both the delay and loop phasing are largely frequency independent providing a directive pattern over a wide frequency range.

The array consists of four identical right triangle shaped wire loops whose vertical sides are each separated and supported by a single non-conductive mast. The loops are arranged around the mast so that one loop points towards the northeast, another to the southeast, another to southwest, and another to the northwest.

The direction and directional mode of the array is commanded by a controller that connects directly to your receiver. The controller has buttons for changing the direction, flipping to the opposite direction, and selecting the directional mode. The directional modes include a Single or UNI-directional mode as well as a dual or BI-directional mode. Visual indicators show the currently selected direction and directional mode. A remote interface is included that enables the controller to be commanded by a computer.

A single RG-6 coaxial feedline connects the controller to the array to power and command the array as well as transport the received signals from the array to the controller.

Ferrite couplers are located along the base of each loop at a specific distance from the mast and connected to balanced feedlines that bring the signals to a switching unit mounted on the mast. Relays in the switching unit route signals from the appropriate combination of loops in response to commands received from the controller. A single delay line also connects to the switching unit to provide the necessary true-time-delay so that signals can be properly combined to achieve the desired directive pattern. The switching unit has a socketed dual stage preamplifier that provides a buffered and matched load for the combiner and boosts the summed signals before they are sent to the controller.

  • For more information, see the "Shared Apex Loop presentation at the Dayton 2014 Antenna Forum." Also, you may be interested in viewing a demonstration of recent experiments with a high RDF version of the Array called the Close-Coupled Shared Apex Loop. See "Part 1" and "Part 2".

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