Section 74.452 - Equipment changes(a) Modifications may be made to an existing authorization in accordance with §§ 1.929 and 1.947 of this chapter.(b) All transmitters initially installed after November 30, 1977, must be certificated for use in this service or other service as specified in § 74.451(a) . 68 FR 12765 , Mar. 17, 2003