Section 73.406 - [Effective on an indefinitely defined 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 .(5) Any digital FM station taking any of the following actions must notify the Commission of such action on Form 2100, Schedule 335-FM:(i) Upon initiation of hybrid digital operation;(ii) Upon initiation of asymmetric sideband operation at any power level. For FM stations employing asymmetric sideband operation as defined in § 73.402(i) , the notification must include a certification that the proposed digital sideband power on each sideband conforms to the Maximum Permissible FM Digital ERP set forth in table 1 to § 73.404(f) , and that the total digital sideband power will not exceed the total power if the digital sideband operation were symmetric. The notifying station may commence asymmetric sideband operation upon filing Form 2100, Schedule 335-FM, and may continue such operation unless notified by the Commission that such operation is not rule-compliant;(iii) Discontinuing asymmetric sideband operation and reverting to symmetric sideband operation. The digital FM station must file Form 2100, Schedule 335-FM within 30 days of discontinuing asymmetric sideband operation; or(iv) Decreasing total digital Effective Radiated Power from a level above -14 dBc to a level at or below -14 dBc. The digital FM station must file Form 2100, Schedule 335-FM within 30 days of decreasing power.(6) Any digital FM station seeking authority to increase total digital Effective Radiated Power above -14 dBc must submit Form 2100, Schedule 335-FM. The submission must include a certification that the proposed FM digital Effective Radiated Power is permitted, using the table set forth in table 1 to § 73.404(f) . Certifications must be based on the most restrictive analog field strength of the proponent at any nearby first-adjacent channel station's 60 dB[MICRO] contour. The station choosing to operate with total digital ERP above -14 dBc may initiate such operation upon approval from the Commission. 85 FR 78027 , Dec. 3, 2020 85 FR 78027 , 12/3/2020; 89 FR 84104 , effective date to be determined