Abstract: A HEMP enclosure includes a recessed coaxial connector interface. The connector interface is located at the bottom of a metallic tube in the chassis wall that functions as a waveguide below cutoff (WBC). The WBC attenuates the electromagnetic pulse threat signal to a benign level when the transmitter enclosure is not inserted for testing. Internal to the chassis, the connector interface includes an omni-directional antenna. A transmitter enclosure includes a wand to plug the transmitter into the connected interface. The transmitter generates an RF signal at a desired frequency range that is then transmitted via a coaxial cable in the wand to the antenna in the chassis.