American National Standard for EMC measurements

What this standard covers and how we test it

ANSI C63.4 is a measurement method, not a limit: it specifies how the table, the cabling, the antenna height scan and the turntable must be arranged so that a Part 15 measurement can be reproduced in another lab. The FCC rules cite it directly, which is why two competent labs testing the same device should land within a few dB of each other.

What the method fixes:

• Table-top and floor-standing EUT set-up, cable routing and termination
• Antenna height scan from 1 m to 4 m and turntable rotation to find the maximum
• Quasi-peak and average detection, plus the 3 m to 10 m distance correction
• Ambient noise validation before the EUT is powered up

We photograph the set-up and keep the pictures with the report. If a result is challenged later, the difference is almost always in the layout, and the answer is a controlled re-test rather than a discussion.

We normally test ANSI C63.4 together with Referenced by FCC: one sample set, one set of test dates, and a single report pack that the declaration of conformity can reference.