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Federal Communications Commission § 73.1590

the licensee must notify the FCC of the (2) FM stations. The total date that normal operation was re- must not exceed 100 percent on peaks stored. If causes beyond the control of of frequent reoccurrence referenced to the licensee prevent restoration of the 75 kHz deviation. However, stations authorized power within 30 days, a re- providing subsidiary communications quest for Special Temporary Authority services using under provi- (see § 73.1635) must be made to the FCC sions of § 73.319 concurrently with the in Washington, DC for additional time of stereophonic or as may be necessary. monophonic programs may increase the peak modulation deviation as fol- [44 FR 58734, Oct. 11, 1979, as amended at 49 lows: FR 22093, May 25, 1984; 49 FR 29069, July 18, 1984; 49 FR 47610, Dec. 6, 1984; 50 FR 26568, (i) The total peak modulation may be June 27, 1985; 50 FR 40015, Oct. 1, 1985; 63 FR increased 0.5 percent for each 1.0 per- 33877, June 22, 1998; 65 FR 30004, May 10, 2000; cent injection modulation. 67 FR 13232, Mar. 21, 2002] (ii) In no event may the modulation of the carrier exceed 110 percent (82.5 § 73.1570 Modulation levels: AM, FM, kHz peak deviation). TV and Class A TV aural. (3) TV and Class A TV stations. In no (a) The percentage of modulation is case shall the total modulation of the to be maintained at as high a level as aural carrier exceed 100% on peaks of is consistent with good quality of frequent recurrence, unless some other transmission and good broadcast serv- peak modulation level is specified in an ice, with maximum levels not to exceed instrument of authorization. For the values specified in paragraph (b). monophonic transmissions, 100% modu- Generally, the modulation should not lation is defined as +/¥25 kHz. be less than 85% on peaks of frequent (c) If a limiting or compression am- recurrence, but where lower modula- plifier is employed to maintain modu- tion levels may be required to avoid ob- lation levels, precaution must be taken jectionable loudness or to maintain the so as not to substantially alter the dy- dynamic range of the program mate- namic characteristics of programs. rial, the degree of modulation may be [44 FR 58735, Oct. 11, 1979, as amended at 47 reduced to whatever level is necessary FR 13165, Mar. 29, 1982; 49 FR 14508, Apr. 12, for this purpose, even though under 1984; 49 FR 15081, Apr. 17, 1984; 49 FR 27147, such circumstances, the level may be July 2, 1984; 49 FR 47610, Dec. 6, 1984; 49 FR substantially less than that which pro- 48312, Dec. 12, 1984; 51 FR 26251, July 22, 1986; duces peaks of frequent recurrence at a 56 FR 64872, Dec. 12, 1991; 65 FR 30004, May 10, level of 85%. 2000] (b) Maximum modulation levels must § 73.1580 Transmission system inspec- meet the following limitations: tions. (1) AM stations. In no case shall the modulation of the carrier Each AM, FM, TV and Class A TV exceed 100% on negative peaks of station licensee or permittee must con- frequent recurrence, or 125% on posi- duct periodic complete inspections of tive peaks at any time. the transmitting system and all re- quired monitors to ensure proper sta- (i) AM stations transmitting stereo- tion operation. phonic programs not exceed the AM maximum stereophonic transmission [65 FR 30004, May 10, 2000] signal modulation specifications of stereophonic system in use. § 73.1590 Equipment performance (ii) For AM stations transmitting te- measurements. lemetry signals for remote control or (a) The licensee of each AM, FM, TV automatic transmission system oper- and Class A TV station, except licens- ation, the amplitude of modulation of ees of Class D non-commercial edu- the carrier by the use of subaudible cational FM stations authorized to op- tones must not be higher than nec- erate with 10 watts or less output essary to effect reliable and accurate power, must make equipment perform- data transmission and may not, in any ance measurements for each main case, exceed 6%. as follows:

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