Section 73.406 - [Effective until an indefinitely delayed date ] Notification(a) Hybrid AM and FM licensees must electronically file a digital notification to the Commission in Washington, DC, within 10 days of commencing IBOC digital operation. (1) All-digital licensees must file a digital notification within 10 days of the following changes: (i) Any reduction in nominal power of an all-digital AM station;(ii) A transition from enhanced to core-only operating mode; or(iii) A reversion from all-digital to hybrid or analog operation.(2) All-digital licensees will not be permitted to commence operation sooner than 30 calendar days from public notice of digital notification of the following changes:(i) The commencement of new all-digital operation;(ii) An increase in nominal power of an all-digital AM station; or(iii) A transition from core-only to enhanced operating mode.(b) Every digital notification must include the following information:(1) The call sign and facility identification number of the station;(2) If applicable, the date on which the new or modified IBOC operation commenced or ceased;(3) The name and telephone number of a technical representative the Commission can call in the event of interference;(4) A certification that the operation will not cause human exposure to levels of radio frequency radiation in excess of the limits specified in § 1.1310 of this chapter and is therefore categorically excluded from environmental processing pursuant to § 1.1306(b) of this chapter. Any station that cannot certify compliance must submit an environmental assessment ("EA") pursuant to § 1.1311 of this chapter and may not commence IBOC operation until such EA is ruled upon by the Commission.(c) Each AM digital notification must also include the following information: (1) A certification that the IBOC DAB facilities conform to applicable nominal power limits and emissions mask limits;(2) The nominal power of the station; if separate analog and digital transmitters are used, the nominal power for each transmitter;(3) If applicable, the amount of any reduction in an AM station's digital carriers;(4) For all-digital stations, the type of notification (all-digital notification, increase in nominal power, reduction in nominal power, transition from core-only to enhanced, transition from enhanced to core-only, reversion from all-digital to hybrid or analog operation);(5) For all-digital stations, if a notification of commencement of new all-digital service or a nominal power change, whether the station is operating in core-only or enhanced mode; and(6) For all-digital stations, a certification that the all-digital station complies with all Emergency Alert System (EAS) requirements in part 11 of this chapter.(d) Each FM digital notification must also include the following information: (1) A certification that the IBOC DAB facilities conform to the HD Radio emissions mask limits;(2) FM digital effective radiated power used and certification that the FM analog effective radiated power remains as authorized;(3) If applicable, the geographic coordinates, elevation data, and license file number of the auxiliary antenna employed by an FM station as a separate digital antenna; and(4) If applicable, for FM systems employing interleaved antenna bays, a certification that adequate filtering and/or isolation equipment has been installed to prevent spurious emissions in excess of the limits specified in § 73.317 . 85 FR 78027 , Dec. 3, 2020