Abstract: TEM horn array apertures are disclosed, comprises a plurality of stamped sheet segments interconnected to form an “egg crate” like array. Each stamped sheet comprises a plurality of TEM horn antennas with a series of cooperating slots, enabling the sheets to be assembled into an “egg crate” design that allows quick and inexpensive building of a TEM horn antenna array. Moreover, the stamped sheet segments are structurally and dimensionally stable, and thus the assembled array may be connected to a guide plane without the need for additional aligning or structural elements. A method of assembling the array is also disclosed.