Federal Communications Commission § 73.311

Free space field strength. The field reproduced in reception of FM stereo- strength that would exist at a point in phonic broadcasts. the absence of waves reflected from the Main channel. The band of fre- earth or other reflecting objects. quencies from 50 to 15,000 Hz which fre- Frequency departure. The amount of quency-modulate the main carrier. variation of a carrier frequency or cen- Pilot subcarrier. A subcarrier that ter frequency from its assigned value. serves as a control signal for use in the Frequency deviation. The peak dif- reception of FM ference between modulated wave and broadcasts. the carrier frequency. Stereophonic separation. The ratio of . A system of the electrical signal caused in sound modulation where the instantaneous channel A to the signal caused in sound radio frequency varies in proportion to channel B by the transmission of only the instantaneous amplitude of the a channel B signal. Channels A and B modulating signal (amplitude of modu- may be any two channels of a stereo- lating signal to be measured after pre- phonic sound broadcast transmission emphasis, if used) and the instanta- system. neous radio frequency is independent of Stereophonic sound. The audio infor- the frequency of the modulating signal. mation carried by plurality of channels Frequency swing. The peak difference arranged to afford the listener a sense between the maximum and the min- of the spatial distribution of sound imum values of the instantaneous fre- sources. Stereophonic sound broad- quency of the carrier wave during mod- casting includes, but is not limited to, ulation. biphonic (two channel), triphonic Multiplex transmission. The term (three channel) and quadrophonic (four ‘‘multiplex transmission’’ means the channel) program services. simultaneous transmission of two or Stereophonic sound subcarrier. A sub- more signals within a single channel. carrier within the FM broadcast Multiplex transmission as applied to baseband used for transmitting signals FM broadcast stations means the for stereophonic sound reception of the transmission of facsimile or other sig- main broadcast program service. nals in addition to the regular broad- Stereophonic sound subchannel. The cast signals. band of frequencies from 23 kHz to 99 Percentage modulation. The ratio of kHz containing sound subcarriers and the actual frequency deviation to the their associated . frequency deviation defined as 100% (c) Visual transmissions. Communica- modulation, expressed in percentage. tions or message transmitted on a sub- For FM broadcast stations, a frequency carrier intended for reception and vis- deviation of ±75kHz is defined as 100% ual presentation on a viewing screen, modulation. teleprinter, facsimile printer, or other (b) Stereophonic sound broadcasting. form of graphic display or record. Cross-talk. An undesired signal occur- (d) Control and telemetry transmissions. ring in one channel caused by an elec- Signals transmitted on a multiplex trical signal in another channel. subcarrier intended for any form of FM stereophonic broadcast. The trans- control and switching functions or for mission of a stereophonic program by a equipment status data and aural or vis- single FM broadcast station utilizing ual alarms. the main channel and a stereophonic [28 FR 13623, Dec. 14, 1963, as amended at 39 subchannel. FR 10575, Mar. 21, 1974; 44 FR 36038, June 20, Left (or right) signal. The electrical 1979; 48 FR 28454, June 22, 1983; 48 FR 29507, output of a or combination June 27, 1983; 48 FR 37216, Aug. 17, 1983; 49 FR of placed so as to convey 45145, Nov. 15, 1984; 57 FR 48333, Oct. 23, 1992; the intensity, time, and location of 62 FR 51058, Sept. 30, 1997] sounds originating predominately to 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

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Form 301 or FCC Form 340, as appro- (c) The U.S. Geological Survey To- priate. pography Quadrangle Sheets may be (b) The field strength contours pro- obtained from the U.S. Geological Sur- vided for in this section shall be con- vey Department of the Interior, Wash- sidered for the following purposes only: ington, DC 20240. The Sectional Aero- (1) In the estimation of coverage re- nautical Charts are available from the sulting from the selection of a par- U.S. Coast and Geodetic Survey, De- ticular transmitter site by an appli- partment of Commerce, Washington, cant for an FM broadcast station. DC 20235. These maps may also be se- (2) In connection with problems of cured from branch offices and from au- coverage arising out of application of thorized agents or dealers in most prin- § 73.3555. cipal cities. (3) In determining compliance with (d) In lieu of maps, the average ter- § 73.315(a) concerning the minimum rain elevation may be computer gen- field strength to be provided over the erated except in cases of dispute, using principal community to be served. elevations from a 30 second, point or (4) In determining compliance with better topographic data file. The file § 73.215 concerning contour protection. must be identified and the data proc- [28 FR 13623, Dec. 14, 1963, as amended at 31 essed for intermediate points along FR 10126, July 27, 1966; 32 FR 11471, Aug. 9, each radial using linear interpolation 1967; 52 FR 10570, Apr. 2, 1987; 54 FR 9802, Mar. techniques. The height above mean sea 8, 1989] level of the antenna site must be ob- tained manually using appropriate § 73.312 Topographic data. topographic maps. (a) In the preparation of the profile [28 FR 13623, Dec. 14, 1963, as amended at 31 graphs previously described, and in de- FR 10126, July 27, 1966; 49 FR 48937, Dec. 17, termining the location and height 1984; 58 FR 44950, Aug. 25, 1993; 63 FR 33877, above mean sea level of the antenna June 22, 1998] site, the elevation or contour intervals shall be taken from United States Geo- § 73.313 Prediction of coverage. logical Survey Topographic Quadrangle (a) All predictions of coverage made Maps, United States Army Corps of En- pursuant to this section shall be made gineers Maps or Tennessee Valley Au- without regard to interference and thority maps, whichever is the latest, shall be made only on the basis of esti- for all areas for which such maps are mated field strengths. available. If such maps are not pub- (b) Predictions of coverage shall be lished for the area in question, the next made only for the same purposes as re- best topographic information should be late to the use of field strength con- used. Topographic data may sometimes tours as specified in § 73.311. be obtained from state and municipal (c) In predicting the distance to the agencies. The data from the Sectional field strength contours, the F(50,50) Aeronautical Charts (including bench field strength chart, Figure 1 of § 73.333 marks) or railroad depot elevations and must be used. The 50% field strength is highway elevations from road maps defined as that value exceeded for 50% may be used where no better informa- of the time. tion is available. In cases where lim- (1) The F(50,50) chart gives the esti- ited topographic data can be obtained, mated 50% field strengths exceeded at use may be made of an altimeter in a 50% of the locations in dB above 1 uV/ car driven along roads extending gen- m. The chart is based on an effective erally radially from the transmitter power radiated from a half-wave dipole site. antenna in free space, that produces an (b) The Commission will not ordi- unattenuated field strength at 1 kilo- narily require the submission of topo- meter of about 107 dB above 1 uV/m graphical maps for areas beyond 24 km (221.4 mV/m). (15 miles) from the antenna site, but (2) To use the chart for other ERP the maps must include the principal values, convert the ordinate scale by city or cities to be served. If it appears the appropriate adjustment in dB. For necessary, additional data may be re- example, the ordinate scale for an ERP quested. of 50 kW should be adjusted by 17 dB [10

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