47 CFR § 80.63
Maintenance of transmitter power
February 16, 2021
(a) The power of each radio transmitter must not be more than that necessary to carry on the service for which the station is licensed.
(b) Except for transmitters using single sideband and independent sideband emissions, each radio transmitter rated by the manufacturer for carrier power in excess of 100 watts must contain the instruments necessary to determine the transmitter power during its operation.