47 CFR § 73.809 - Interference protection to full service FM stations.
(a) If a full service commercial or NCE FM facility application is filed subsequent to the filing of an LPFM station facility application, such full service station is protected against any condition of interference to the direct reception of its signal that is caused by such LPFM station operating on the same channel or first-adjacent channel provided that the interference is predicted to occur and actually occurs within:
(1) The 3.16 mV/m (70 dBu) contour of such full service station;
(2) The community of license of such full service station; or
(3) Any area of the community of license of such full service station that is predicted to receive at least a 1 mV/m (60 dBu) signal. Predicted interference shall be calculated in accordance with the ratios set forth in § 73.215 paragraphs (a)(1) and (a)(2). Intermediate frequency (IF) channel interference overlap will be determined based upon overlap of the 91 dBu F(50,50) contours of the FM and LPFM stations. Actual interference will be considered to occur whenever reception of a regularly used signal is impaired by the signal radiated by the LPFM station.
(b) An LPFM station will be provided an opportunity to demonstrate in connection with the processing of the commercial or NCE FM application that interference as described in paragraph (a) of this section is unlikely. If the LPFM station fails to so demonstrate, it will be required to cease operations upon the commencement of program tests by the commercial or NCE FM station.
(c) Complaints of actual interference by an LPFM station subject to paragraphs (a) and (b) of this section must be served on the LPFM licensee and the Federal Communications Commission, attention Audio Services Division. The LPFM station must suspend operations within twenty-four hours of the receipt of such complaint unless the interference has been resolved to the satisfaction of the complainant on the basis of suitable techniques. An LPFM station may only resume operations at the direction of the Federal Communications Commission. If the Commission determines that the complainant has refused to permit the LPFM station to apply remedial techniques that demonstrably will eliminate the interference without impairment of the original reception, the licensee of the LPFM station is absolved of further responsibility for the complaint.
(d) It shall be the responsibility of the licensee of an LPFM station to correct any condition of interference that results from the radiation of radio frequency energy outside its assigned channel. Upon notice by the FCC to the station licensee or operator that such interference is caused by spurious emissions of the station, operation of the station shall be immediately suspended and not resumed until the interference has been eliminated. However, short test transmissions may be made during the period of suspended operation to check the efficacy of remedial measures.
(e) In each instance where suspension of operation is required, the licensee shall submit a full report to the FCC in Washington, DC, after operation is resumed, containing details of the nature of the interference, the source of the interfering signals, and the remedial steps taken to eliminate the interference.