47 CFR Ch. I (10–1–13 Edition) § 73.297

§ 73.297 47 CFR Ch. I (10–1–13 Edition)

applicable to the service. Responsi- is kept at all times within 2 Hz of the bility for making the initial deter- authorized frequency. minations of whether a particular ac- [48 FR 28454, June 22, 1983, and 48 FR 38479, tivity is common carriage rests with Aug. 24, 1983] the FM station licensee. Initial deter- minations by licensees are subject to § 73.310 FM technical definitions. FCC examination and may be reviewed (a) Frequency modulation. Antenna at the FCC’s discretion. height above average terrain (HAAT). (c) Subsidiary communications serv- HAAT is calculated by: determining ices are of a secondary nature under the average of the antenna heights the authority of the FM station au- above the terrain from 3 to 16 kilo- thorization, and the authority to pro- meters (2 to 10 miles) from the antenna vide such communications services for the eight directions evenly spaced may not be retained or transferred in for each 45° of azimuth starting with any manner separate from the station’s True North (a different antenna height authorization. The grant or renewal of will be determined in each direction an FM station permit or license is not from the antenna): and computing the furthered or promoted by proposed or average of these separate heights. In past services. The permittee or licensee some cases less than eight directions must establish that the broadcast oper- may be used. (See § 73.313(d).) Where ation is in the public interest wholly circular or elliptical polarization is apart from the subsidiary communica- used, the antenna height above average tions services provided. terrain must be based upon the height (d) The station identification, de- of the radiation of the antenna that layed recording and sponsor identifica- transmits the horizontal component of tion announcements required by radiation. §§ 73.1201, 73.1208, and 73.1212 are not ap- Antenna power gain. The square of the plicable to material transmitted under ratio of the root-mean-square (RMS) an SCA. free space field strength produced at 1 (e) The licensee or permittee must kilometer in the horizontal plane in retain control over all material trans- millivolts per meter for 1 kW antenna mitted in a broadcast mode via the sta- input power to 221.4 mV/m. This ratio tion’s facilities, with the right to re- is expressed in decibels (dB). If speci- ject any material that it deems inap- fied for a particular direction, antenna propriate or undesirable. power gain is based on that field [48 FR 28454, June 22, 1983, as amended at 48 strength in the direction only. FR 44805, Sept. 30, 1983; 49 FR 33663, Aug. 15, Auxiliary facility. An auxiliary facil- 1984; 50 FR 32416, Aug. 12, 1985; 57 FR 48333, ity is an antenna separate from the Oct. 23, 1992] main facility’s antenna, permanently installed on the same tower or at a dif- § 73.297 FM stereophonic sound broad- ferent location, from which a station casting. may broadcast for short periods with- (a) An FM broadcast station may, out prior Commission authorization or without specific authority from the notice to the Commission while the FCC, transmit stereophonic (biphonic, main facility is not in operation (e.g., quadraphonic, etc.) sound programs where tower work necessitates turning upon installation of stereophonic sound off the main antenna or where light- transmitting equipment under the pro- ning has caused damage to the main visions of §§ 2.1001, 73.322, and 73.1590 of antenna or transmission system) (See the Rules. Prior to commencement of § 73.1675). stereophonic sound broadcasting, Center frequency. The term ‘‘center equipment performance measurements frequency’’ means: must be made to ensure that the trans- (1) The average frequency of the mitted signal complies with all appli- emitted wave when modulated by a si- cable rules and standards. nusoidal signal. (b) Each licensee or permittee engag- (2) The frequency of the emitted wave ing in multichannel broadcasting must without modulation. measure the pilot subcarrier frequency Composite antenna pattern. The com- as often as necessary to ensure that it posite antenna pattern is a relative

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field horizontal plane pattern for 360 telephone emissions intended to be re- degrees of azimuth, for which the value ceived by the general public. at a particular azimuth is the greater Field strength. The electric field of the horizontally polarized or strength in the horizontal plane. vertically polarized component relative Free space field strength. The field field values. The composite antenna strength that would exist at a point in pattern is normalized to a maximum of the absence of waves reflected from the unity (1.000) relative field. earth or other reflecting objects. Composite baseband signal. A signal Frequency departure. The amount of which is composed of all program and variation of a carrier frequency or cen- other communications signals that fre- ter frequency from its assigned value. quency modulates the FM carrier. Frequency deviation. The peak dif- Effective radiated power. The term ference between modulated wave and ‘‘effective radiated power’’ means the the carrier frequency. product of the antenna power (trans- Frequency modulation. A system of mitter output power less transmission modulation where the instantaneous line loss) times: (1) The antenna power radio frequency varies in proportion to gain, or (2) the antenna field gain the instantaneous amplitude of the squared. Where circular or elliptical modulating signal (amplitude of modu- polarization is employed, the term ef- lating signal to be measured after pre- fective radiated power is applied sepa- emphasis, if used) and the instanta- rately to the horizontal and vertical neous radio frequency is independent of components of radiation. For alloca- the frequency of the modulating signal. tion purposes, the effective radiated power authorized is the horizontally Frequency swing. The peak difference polarized component of radiation only. between the maximum and the minimum values of the instantaneous fre- Equivalent isotropically radiated power quency of the carrier wave during mod- (EIRP). The term ‘‘equivalent isotropically radiated power (also ulation. known as ‘‘effective radiated power Multiplex transmission. The term above isotropic) means the product of ‘‘multiplex transmission’’ means the the antenna input power and the an- simultaneous transmission of two or tenna gain in a given direction relative more signals within a single channel. to an isotropic antenna. Multiplex transmission as applied to FM Blanketing. Blanketing is that FM broadcast stations means the form of interference to the reception of transmission of facsimile or other sig- other broadcast stations which is nals in addition to the regular broad- caused by the presence of an FM broadcast signals. cast signal of 115 dBu (562 mV/m) or Percentage modulation. The ratio of greater signal strength in the area ad- the actual frequency deviation to the jacent to the antenna of the transmit- frequency deviation defined as 100% ting station. The 115 dBu contour is re- modulation, expressed in percentage. ferred to as the blanketing contour and For FM broadcast stations, a frequency the area within this contour is referred deviation of ±75kHz is defined as 100% to as the blanketing area. modulation. FM broadcast band. The band of fre- (b) Stereophonic sound broadcasting. quencies extending from 88 to 108 MHz, Cross-talk. An undesired signal occur- which includes those assigned to non- ring in one channel caused by an elec- commercial educational broadcasting. trical signal in another channel. FM broadcast channel. A band of fre- FM stereophonic broadcast. The trans- quencies 200 kHz wide and designated mission of a stereophonic program by a by its center frequency. Channels for single FM broadcast station utilizing FM broadcast stations begin at 88.1 the main channel and a stereophonic MHz and continue in successive steps subchannel. of 200 kHz to and including 107.9 MHz. Left (or right) signal. The electrical FM broadcast station. A station em- output of a microphone or combination ploying frequency modulation in the of microphones placed so as to convey FM broadcast band and licensed pri- the intensity, time, and location of marily for the transmission of radio- sounds originating predominately to

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the listener’s left (or right) of the cen- § 73.311 Field strength contours. ter of the performing area. (a) Applications for FM broadcast au- Left (or right) stereophonic channel. thorizations must show the field The left (or right) signal as electrically strength contours required by FCC reproduced in reception of FM stereo- Form 301 or FCC Form 340, as appro- phonic broadcasts. priate. Main channel. The band of fre- (b) The field strength contours pro- quencies from 50 to 15,000 Hz which fre- vided for in this section shall be con- quency-modulate the main carrier. sidered for the following purposes only: Pilot subcarrier. A subcarrier that (1) In the estimation of coverage re- serves as a control signal for use in the sulting from the selection of a par- reception of FM stereophonic sound ticular transmitter site by an appli- broadcasts. cant for an FM broadcast station. Stereophonic separation. The ratio of (2) In connection with problems of coverage arising out of application of the electrical signal caused in sound § 73.3555. channel A to the signal caused in sound (3) In determining compliance with channel B by the transmission of only § 73.315(a) concerning the minimum a channel B signal. Channels A and B field strength to be provided over the may be any two channels of a stereo- principal community to be served. phonic sound broadcast transmission (4) In determining compliance with system. § 73.215 concerning contour protection. Stereophonic sound. The audio information carried by plurality of channels [28 FR 13623, Dec. 14, 1963, as amended at 31 FR 10126, July 27, 1966; 32 FR 11471, Aug. 9, arranged to afford the listener a sense 1967; 52 FR 10570, Apr. 2, 1987; 54 FR 9802, Mar. of the spatial distribution of sound 8, 1989] sources. Stereophonic sound broadcasting includes, but is not limited to, § 73.312 Topographic data. biphonic (two channel), triphonic (a) In the preparation of the profile (three channel) and quadrophonic (four graphs previously described, and in de- channel) program services. termining the location and height Stereophonic sound subcarrier. A sub- above mean sea level of the antenna carrier within the FM broadcast site, the elevation or contour intervals baseband used for transmitting signals shall be taken from United States Geo- for stereophonic sound reception of the logical Survey Topographic Quadrangle main broadcast program service. Maps, United States Army Corps of En- Stereophonic sound subchannel. The gineers Maps or Tennessee Valley Au- band of frequencies from 23 kHz to 99 thority maps, whichever is the latest, kHz containing sound subcarriers and for all areas for which such maps are their associated sidebands. available. If such maps are not pub- lished for the area in question, the next (c) Visual transmissions. Communica- best topographic information should be tions or message transmitted on a sub- used. Topographic data may sometimes carrier intended for reception and vis- be obtained from state and municipal ual presentation on a viewing screen, agencies. The data from the Sectional teleprinter, facsimile printer, or other Aeronautical Charts (including bench form of graphic display or record. marks) or railroad depot elevations and (d) Control and telemetry transmissions. highway elevations from road maps Signals transmitted on a multiplex may be used where no better informa- subcarrier intended for any form of tion is available. In cases where lim- control and switching functions or for ited topographic data can be obtained, equipment status data and aural or vis- use may be made of an altimeter in a ual alarms. car driven along roads extending gen- erally radially from the transmitter [28 FR 13623, Dec. 14, 1963, as amended at 39 FR 10575, Mar. 21, 1974; 44 FR 36038, June 20, site. 1979; 48 FR 28454, June 22, 1983; 48 FR 29507, (b) The Commission will not ordi- June 27, 1983; 48 FR 37216, Aug. 17, 1983; 49 FR narily require the submission of topo- 45145, Nov. 15, 1984; 57 FR 48333, Oct. 23, 1992; graphical maps for areas beyond 24 km 62 FR 51058, Sept. 30, 1997] (15 miles) from the antenna site, but

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