Can I change antennas or antenna placement after certification without regulatory impact?

Only if the change does not alter compliance assumptions. Antenna type, gain, placement, grounding, and matching directly affect radiated emissions and RF exposure. Even when a grant does not specify antennas, the final product must still comply with RF exposure and emissions limits. Moving an antenna closer to users, switching to a higher-gain antenna, or changing the ground reference can push the product out of compliance. In both FCC and ISED regimes, antenna changes are one of the most common causes of post-certification noncompliance because teams treat them as mechanical design decisions rather than regulatory ones.