Radiated emissions testing is designed to measure the electromagnetic energy emitted from a device under test (DUT) to ensure it does not interfere with other electronic equipment. The setup typically takes place in a controlled environment such as an anechoic chamber, which absorbs reflections to simulate free-space conditions, or an open-area test site (OATS). The DUT is placed on a non-conductive turntable, often 0.8-1.5 meters above the ground plane, allowing for 360° rotation to capture emissions in all directions. Measurement antennas, usually broadband biconical, log-periodic, or loop antennas depending on the frequency range, are positioned at a fixed distance from the DUT (commonly 3 or 10 meters) and can be raised or lowered to identify maximum emission levels.

The DUT is powered and operated in its typical modes to ensure representative emissions are captured. Signals received by the antenna are fed into a spectrum analyzer or EMI receiver, which records the amplitude of emissions across the frequency range of interest (often 30 MHz to 1 GHz for low-frequency emissions and up to several GHz for higher-frequency devices). Measurements are repeated with different antenna polarizations and DUT orientations to ensure the worst-case emissions are identified. Grounding, cable routing, and environmental controls are carefully managed to avoid introducing measurement errors, and the entire setup must comply with international standards such as CISPR 11, CISPR 32, EN 55032, or FCC Part 15 to validate compliance.