Section 27.1423 - Protection of incumbent operations(a) To protect incumbent earth stations from out-of-band emissions from fixed stations, base stations and mobiles, the power flux density (PFD) of any emissions within the 4000-4200 MHz band must not exceed -124 dBW/m2/MHz as measured at the earth station antenna.(b) To protect incumbent earth stations from blocking, the power flux density (PFD) of any emissions within the 3700-3980 MHz band must not exceed -16 dBW/m2/MHz as measured at the earth station antenna.(c) All 3.7 GHz Service licensees, prior to initiating operations from any base or fixed station, must coordinate cochannel frequency usage with all incumbent Telemetry, Tracking, and Command (TT&C) earth stations within a 70 km radius. The licensee must ensure that the aggregated power from its operations meets an interference to noise ratio (I/N) of -6 dB to the TT&C earth station receiver. A base station's operation will be defined as cochannel when any of the 3.7 GHz Service licensee's authorized frequencies are separated from the center frequency of the TT&C earth station by less than 150% of the maximum emission bandwidth in use by the TT&C earth station.(d) All 3.7 GHz Service licensees operating on an adjacent channel to an incumbent TT&C earth station must ensure that the aggregated power from its operations meets an interference to noise ratio (I/N) of -6 dB to the TT&C earth station receiver.(e) To protect incumbent TT&C earth stations from blocking, the power flux density (PFD) of any emissions within the 3700-3980 MHz band must not exceed -16 dBW/m2/MHz as measured at the TT&C earth station antenna.