Federal Communications Commission § 73.333

any mechanical or electrical modifica- stereophonic subcarrier at 38 kHz must tions in the transmitter FM exciter be used. circuits. (5) The stereophonic subcarrier at 38 (f) Stations installing multiplex sub- kHz must be suppressed to a level less carrier transmitting equipment must than 1% modulation of the main car- ensure the proper suppression of spu- rier. rious or harmonic radiations. See (6) The modulating signal for the re- §§ 73.317, 73.1590 and 73.1690. If the sub- quired stereophonic subcarrier must be carrier operation causes the station’s equal to the difference of the left and transmissions not to comply with the right signals. technical provisions for FM broadcast stations or causes harmful interference (7) The following modulation levels to other communication services, the apply: licensee or permittee must correct the (i) When a signal exists in only one problem promptly or cease operation. channel of a two channel (biphonic) The licensee may be required to verify sound transmission, modulation of the the corrective measures with sup- carrier by audio components within the porting data. Such data must be re- baseband range of 50 Hz to 15 kHz shall tained at the station and be made not exceed 45% and modulation of the available to the FCC upon request. carrier by the sum of the amplitude [48 FR 28455, June 22, 1983, as amended at 48 modulated subcarrier in the baseband FR 37216, Aug. 17, 1983; 49 FR 15080, Apr. 17, range of 23 kHz to 53 kHz shall not ex- 1984; 49 FR 38131, Sept. 27, 1984; 50 FR 1534, ceed 45%. Jan. 11, 1985; 51 FR 17029, May 8, 1986; 57 FR (ii) When a signal exists in only one 48333, Oct. 23, 1992] channel of a trans- § 73.322 FM stereophonic sound trans- mission having more than one stereo- mission standards. phonic subcarrier in the baseband, the modulation of the carrier by audio (a) An FM broadcast station shall not components within the audio baseband use 19 kHz ±20 Hz, except as the stereo- phonic pilot frequency in a trans- range of 23 kHz to 99 kHz shall not ex- mission system meeting the following ceed 53% with total modulation not to parameters: exceed 90%. (1) The modulating signal for the (b) Stations not transmitting stereo main channel consists of the sum of with the method described in (a), must the right and left signals. limit the main carrier deviation caused (2) The pilot subcarrier at 19 kHz ±2 by any modulating signals occupying Hz, must frequency modulate the main the band 19 kHz ±20 Hz to 125 Hz. carrier between the limits of 8 and 10 (c) All stations, regardless of the percent. stereophonic transmission system (3) One stereophonic subcarrier must used, must not exceed the maximum be the second harmonic of the pilot modulation limits specified in subcarrier (i.e., 38 kHz) and must cross § 73.1570(b)(2). Stations not using the the time axis with a positive slope si- method described in (a), must limit the multaneously with each crossing of the modulation of the carrier by audio time axis by the pilot subcarrier. Addi- components within the audio baseband tional stereophomic subcarriers are not range of 23 kHz to 99 kHz to not exceed precluded. 53%. (4) Double , suppressed-car- rier, of the [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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