Abstract: A testing means for determining susceptibility to radiated energy and leakage of energy from a device having a conductive surface comprising a stripline unit for transmitting radiant energy in the principal transverse electromagnetic mode including a first conductive ground plane element, a second conductive ground plane element spaced from and parallel to the first ground plane element, and a plane center conductor element positioned intermediate and parallel to the first and second ground plane elements. The stripline unit has first and second end sections providing energy coupling means, and an intermediate section between the end sections for transmitting energy therealong. A portion of the first ground plane element of the intermediate section of the stripline unit has an opening for being closed by a conductive surface of a device which is to be tested and which effectively provides a portion of ground plane of the stripline unit.