Federal Communications Commission § 73.322

multiplex subcarriers and their signifi- §§ 73.317, 73.1590 and 73.1690. If the sub- cant must be within the carrier operation causes the station’s range of 20 kHz to 99 kHz. transmissions not to comply with the (2) During pro- technical provisions for FM broadcast gram transmissions (see § 73.322), multi- stations or causes harmful interference plex subcarriers and their significant to other communication services, the sidebands must be within the range of licensee or permittee must correct the 53 kHz to 99 kHz. problem promptly or cease operation. (3) During periods when broadcast The licensee may be required to verify programs are not being transmitted, the corrective measures with sup- multiplex subcarriers and their signifi- porting data. Such data must be re- cant sidebands must be within the tained at the station and be made range of 20 kHz to 99 kHz. available to the FCC upon request. (d) Subcarrier injection. (1) During [48 FR 28455, June 22, 1983, as amended at 48 monophonic program transmissions, FR 37216, Aug. 17, 1983; 49 FR 15080, Apr. 17, modulation of the carrier by the arith- 1984; 49 FR 38131, Sept. 27, 1984; 50 FR 1534, metic sum of all subcarriers may not Jan. 11, 1985; 51 FR 17029, May 8, 1986; 57 FR exceed 30% referenced to 75 kHz modu- 48333, Oct. 23, 1992] lation deviation. However, the modula- tion of the carrier by the arithmetic § 73.322 FM stereophonic sound trans- sum of all subcarriers above 75 kHz mission standards. may not modulate the carrier by more (a) An FM broadcast station shall not than 10%. use 19 kHz ±20 Hz, except as the stereo- (2) During stereophonic program phonic pilot frequency in a trans- transmissions, modulation of the car- mission system meeting the following rier by the arithmetic sum of all sub- parameters: carriers may not exceed 20% referenced (1) The modulating signal for the to 75 kHz modulation deviation. How- main channel consists of the sum of ever, the modulation of the carrier by the right and left signals. the arithmetic sum of all subcarriers (2) The pilot subcarrier at 19 kHz ±2 above 75 kHz may not modulate the Hz, must frequency modulate the main carrier by more than 10%. carrier between the limits of 8 and 10 (3) During periods when no broadcast percent. program service is transmitted, modu- (3) One stereophonic subcarrier must lation of the carrier by the arithmetic be the second harmonic of the pilot sum of all subcarriers may not exceed subcarrier (i.e., 38 kHz) and must cross 30% referenced to 75 kHz modulation the time axis with a positive slope si- deviation. However, the modulation of multaneously with each crossing of the the carrier by the arithmetic sum of all time axis by the pilot subcarrier. Addi- subcarriers above 75 kHz may not mod- tional stereophomic subcarriers are not ulate the carrier by more than 10%. precluded. (4) Total modulation of the carrier (4) Double , suppressed-car- wave during transmission of multiplex rier, of the subcarriers used for subsidiary commu- stereophonic subcarrier at 38 kHz must nications services must comply with be used. the provisions § 73.1570(b). (5) The stereophonic subcarrier at 38 (e) Subcarrier generators may be in- kHz must be suppressed to a level less stalled and used with a type accepted than 1% modulation of the main car- FM broadcast transmitter without spe- rier. cific authorization from the FCC pro- (6) The modulating signal for the re- vided the generator can be connected quired stereophonic subcarrier must be to the transmitter without requiring equal to the difference of the left and any mechanical or electrical modifica- right signals. tions in the transmitter FM exciter (7) The following modulation levels circuits. apply: (f) Stations installing multiplex sub- (i) When a signal exists in only one carrier transmitting equipment must channel of a two channel (biphonic) ensure the proper suppression of spu- sound transmission, modulation of the rious or harmonic radiations. See carrier by audio components within the

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baseband range of 50 Hz to 15 kHz shall (b) Stations not transmitting stereo not exceed 45% and modulation of the with the method described in (a), must carrier by the sum of the amplitude limit the main carrier deviation caused modulated subcarrier in the baseband by any modulating signals occupying range of 23 kHz to 53 kHz shall not ex- the band 19 kHz ±20 Hz to 125 Hz. ceed 45%. (c) All stations, regardless of the (ii) When a signal exists in only one stereophonic transmission system channel of a stereophonic sound trans- used, must not exceed the maximum mission having more than one stereo- modulation limits specified in § 73.1570(b)(2). Stations not using the phonic subcarrier in the baseband, the method described in (a), must limit the modulation of the carrier by audio modulation of the carrier by audio components within the audio baseband components within the audio baseband range of 23 kHz to 99 kHz shall not ex- range of 23 kHz to 99 kHz to not exceed ceed 53% with total modulation not to 53%. exceed 90%. [51 FR 17029, May 8, 1986]

§ 73.333 Engineering charts. This section consists of the following Figures 1, 1a, 2, and slider 4 and 5.

NOTE: The figures reproduced herein, due to their small scale, are not to be used in connec- tion with material submitted to the F.C.C.

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