47 CFR § 73.1665 - Main transmitters.
(a) Each AM, FM, TV and Class A TV broadcast station must have at least one main transmitter which complies with the provisions of the transmitter technical requirements for the type and class of station. A main transmitter is one which is used for regular program service having power ratings appropriate for the authorized operating power(s).
(b) There is no maximum manufacturer-rated power limit for AM, FM, TV or Class A TV station transmitters.
(c) A licensee may, without further authority or notification to the FCC, replace an existing main transmitter or install additional main transmitter(s) for use with the authorized antenna if the replacement or additional transmitter(s) has been approved with Supplier's Declaration of Conformity. Within 10 days after commencement of regular use of the replacement or additional transmitter(s), equipment performance measurements, as prescribed for the type of station are to be completed.
The verification procedure has been replaced by Supplier's Declaration of Conformity. Transmitters previously authorized under subpart J of this chapter may remain in use. See § 2.950 of this chapter.
Pending the availability of AM broadcast transmitters that are authorized for use in the 1605-1705 kHz band, transmitters that are approved or verified for use in the 535-1605 kHz band may be utilized in the 1605-1705 kHz band if it is shown that the requirements of § 73.44 have been met. Equipment authorization for the transmitter will supersede the applicability of this note.