§ 73.1 47 CFR Ch. I (10–1–10 Edition)

Subpart J—Class A Television Broadcast Subpart M—Digital Broadcast Television Stations Redistribution Control 73.6000 Definitions. 73.9000 Definitions. 73.6001 Eligibility and service requirements. 73.9001 Redistribution control of digital tel- 73.6002 Licensing requirements. evision broadcasts. 73.6003–73.6005 [Reserved] 73.9002 Sale or distribution of demodulators, 73.6006 Channel assignments. covered demodulator products, and pe- 73.6007 Power limitations. ripheral TSP products. 73.6008 Distance computations. 73.9003 Compliance requirements for cov- 73.6010 Class A TV station protected con- ered demodulator products: Unscreened tour. content. 73.6011 Protection of TV broadcast stations. 73.9004 Compliance requirements for cov- 73.6012 Protection of Class A TV, low power ered demodulator products: Marked con- TV, and TV translator stations. tent. 73.6013 Protection of DTV stations. 73.9005 Compliance requirements for cov- 73.6014 Protection of digital Class A TV sta- ered demodulator products: Audio. tions. 73.9006 Add-in covered demodulator prod- 73.6016 Digital Class A TV station protec- ucts. tion of TV broadcast stations. 73.9007 Robustness requirements for covered 73.6017 Digital Class A TV station protec- demodulator products. tion of Class A TV and digital Class A TV 73.9008 Interim approval of authorized dig- stations. ital output protection technologies and 73.6018 Digital Class A TV station protec- authorized recording methods. tion of DTV stations. 73.9009 Manufacture for exportation. 73.6019 Digital Class A TV station protec- ALPHABETICAL INDEX—PART 73 tion of low power TV, TV translator, dig- ital low power TV and digital TV trans- AUTHORITY: 47 U.S.C. 154, 303, 334, 336, and lator stations. 339. 73.6020 Protection of stations in the land mobile service. 73.6022 Negotiated interference and reloca- Subpart A—AM Broadcast Stations tion agreements. 73.6023 Distributed transmission systems. § 73.1 Scope. 73.6024 Transmission standards and system This subpart contains those rules requirements. which apply exclusively to the AM 73.6025 system and station loca- broadcast service and are in addition to tion. those rules in Subpart H which are 73.6026 Broadcast regulations applicable to Class A television stations. common to all AM, FM and TV broad- 73.6027 Class A TV notifications concerning cast services, commercial and non- interference to radio astronomy, re- commercial. search and receiving installations. [47 FR 8587, Mar. 1, 1982] Subpart K—Application and Selection Pro- § 73.14 AM broadcast definitions. cedures for Reserved Noncommercial Educational Channels, and for Certain AM broadcast band. The band of fre- Applications for Noncommercial Edu- quencies extending from 535 to 1705 cational Stations on Non-Reserved kHz. Channels AM broadcast channel. The band of frequencies occupied by the carrier and 73.7000 Definition of terms (as used in sub- the upper and lower sidebands of an part K only). AM broadcast signal with the carrier 73.7001 Services subject to evaluation by point system. frequency at the center. Channels are 73.7002 Fair distribution of service on re- designated by their assigned carrier served band FM channels. frequencies. The 117 carrier frequencies 73.7003 Point system selection procedures. assigned to AM broadcast stations 73.7004 Petitions to deny tentative se- begin at 540 kHz and progress in 10 kHz lectee(s). steps to 1700 kHz. (See § 73.21 for the 73.7005 Holding period. classification of AM broadcast chan- nels). Subpart L—Digital Broadcast Television AM broadcast station. A broadcast sta- Redistribution Control tion licensed for the dissemination of 73.8000 Incorporation by reference. radio communications intended to be

10

VerDate Mar<15>2010 10:45 Nov 16, 2010 Jkt 220203 PO 00000 Frm 00020 Fmt 8010 Sfmt 8010 Y:\SGML\220203.XXX 220203 WReier-Aviles on DSKGBLS3C1PROD with CFR Federal Communications Commission § 73.14

received by the public and operated on may be accepted under conditions pre- a channel in the AM broadcast band. scribed by the FCC. Amplitude modulated stage. The radio- Critical hours. The two hour period frequency stage to which the modu- immediately following local sunrise lator is coupled and in which the car- and the two hour period immediately rier wave is modulated in accordance preceding local sunset. with the system of amplitude modula- Daytime. The period of time between tion and the characteristics of the local sunrise and local sunset. modulating wave. Effective field; Effective field strength. Amplitude modulator stage. The last The root-mean-square (RMS) value of amplifier stage of the modulating wave the inverse distance fields at a distance amplitude modulates a radio-frequency of 1 kilometer from the antenna in all stage. directions in the horizontal plane. The Antenna current. The radio-frequency term ‘‘field strength’’ is synonymous current in the antenna with no modu- with the term ‘‘field intensity’’ as con- lation. tained elsewhere in this Part. Equipment performance measurements. Antenna input power. The product of The measurements performed to deter- the square of the antenna current and mine the overall performance charac- the antenna resistance at the point teristics of a broadcast transmission where the current is measured. system from point of program origina- Antenna resistance. The total resist- tion at main studio to sampling of sig- ance of the transmitting antenna sys- nal as radiated. (See § 73.1590) tem at the operating frequency and at Experimental period. the time between the point at which the antenna current 12 midnight local time and local sun- is measured. rise, used by AM stations for tests, Auxiliary facility. An auxiliary facil- maintenance and experimentation. ity is an AM antenna tower(s) separate Frequency departure. The amount of from the main facility’s antenna variation of a carrier frequency or cen- tower(s), permanently installed at the ter frequency from its assigned value. same site or at a different location, Incidental phase . The peak from which an AM station may broad- phase deviation (in radians) resulting cast for short periods without prior from the process of amplitude modula- Commission authorization or notice to tion. the Commission while the main facil- Input power. Means the product of the ity is not in operation (e.g., where direct voltage applied to the last radio tower work necessitates turning off the stage and the total direct current flow- main antenna or where lightning has ing to the last radio stage, measured caused damage to the main antenna or without modulation. transmission system) (See § 73.1675). Intermittent service area. Means the Blanketing. The interference which is area receiving service from the caused by the presence of an AM broad- groundwave of a broadcast station but cast signal of one volt per meter (V/m) beyond the primary service area and or greater strengths in the area adja- subject to some interference and fad- cent to the antenna of the transmit- ing. ting station. The 1 V/m contour is re- Last radio stage. The radio-frequency ferred to as the blanket contour and power amplifier stage which supplies the area within this contour is referred power to the antenna. to as the blanket area. Left (or right) signal. The electrical Carrier-amplitude regulation (Carrier output of a microphone or combination shift). The change in amplitude of the of microphones placed so as to convey carrier wave in an amplitude-modu- the intensity, time, and location of lated transmitter when modulation is sounds originated predominately to the applied under conditions of symmet- listener’s left (or right) of the center of rical modulation. the performing area. Combined audio harmonics. The arith- Left (or right) stereophonic channel. metical sum of the amplitudes of all The left (or right) signal as electrically the separate harmonic components. reproduced in reception of AM stereo- Root sum square harmonic readings phonic broadcasts.

11

VerDate Mar<15>2010 10:45 Nov 16, 2010 Jkt 220203 PO 00000 Frm 00021 Fmt 8010 Sfmt 8010 Y:\SGML\220203.XXX 220203 WReier-Aviles on DSKGBLS3C1PROD with CFR § 73.14 47 CFR Ch. I (10–1–10 Edition)

Main channel. The band of audio fre- M = C¥MIN × 100 quencies from 50 to 10,000 Hz which am- ————–—––— plitude modulates the carrier. c Maximum percentage of modulation. Where: The greatest percentage of modulation M = Modulation level in percent. that may be obtained by a transmitter MAX = Instantaneous maximum level of the modulated radio frequency envelope. without producing in its output, MIN = Instantaneous minimum level of the harmonics of the modulating frequency modulated radio frequency envelope. in excess of those permitted by these C = (Carrier) level of radio frequency enve- regulations. (See § 73.1570) lope without modulation. Maximum rated carrier power. The Plate modulation. The modulation maximum power at which the trans- produced by introduction of the modu- mitter can be operated satisfactorily lating wave into the plate circuit of and is determined by the design of the any tube in which the carrier fre- transmitter and the type and number quency wave is present. of vacuum tubes or other amplifier de- Primary service area. Means the serv- vices used in the last radio stage. ice area of a broadcast station in which Model I facility. A station operating the groundwave is not subject to objec- in the 1605–1705 kHz band featuring tionable interference or objectionable fulltime operation with stereo, com- . petitive technical quality, 10 kW day- Proof of performance measurements or time power, 1 kW nighttime power, antenna proof of performance measure- non-directional antenna (or a simple ments. The measurements of field directional antenna system), and sepa- strengths made to determine the radi- rated by 400–800 km from other co- ation pattern or characteristics of an channel stations. AM directional antenna system. Model II facility. A station operating Secondary service area. Means the in the 535–1605 kHz band featuring service area of a broadcast station fulltime operation, competitive tech- served by the and not subject nical quality, wide area daytime cov- to objectionable interference and in erage with nighttime coverage at least which the signal is subject to intermit- 15% of the daytime coverage. tent variations in strength. Nighttime. The period of time between Stereophonic channel. The band of local sunset and local sunrise. audio frequencies from 50 to 10,000 Hz Nominal power. The antenna input containing the stereophonic informa- power less any power loss through a tion which modulates the radio fre- dissipative network and, for directional quency carrier. antennas, without consideration of ad- Stereophonic crosstalk. An undesired justments specified in paragraphs (b)(1) signal occurring in the main channel and (b)(2) of § 73.51 of the rules. How- from modulation of the stereophonic ever, for AM broadcast applications channel or that occurring in the granted or filed before June 3, 1985, stereophonic channel from modulation nominal power is specified in a system of the main channel. of classifications which include the fol- Stereophonic pilot tone. An audio tone lowing values: 50 kW, 25 kW, 10 kW, 5 of fixed or variable frequency modu- kW, 2.5 kW, 1 kW, 0.5 kW, and 0.25 kW. lating the carrier during the trans- The specified nominal power for any mission of stereophonic programs. station in this group of stations will be Stereophonic separation. The ratio of retained until action is taken on or the electrical signal caused in the right after June 3, 1985, which involves a (or left) stereophonic channel to the change in the technical facilities of the electrical signal caused in the left (or station. right) stereophonic channel by the Percentage modulation (amplitude) transmission of only a right (or left) In a positive direction: signal. Sunrise and sunset. For each par- M = MAX¥C × 100 ticular location and during any par- ————––—––— ticular month, the time of sunrise and c sunset as specified in the instrument of In a negative direction: authorization (See § 73.1209).

12

VerDate Mar<15>2010 10:45 Nov 16, 2010 Jkt 220203 PO 00000 Frm 00022 Fmt 8010 Sfmt 8010 Y:\SGML\220203.XXX 220203 WReier-Aviles on DSKGBLS3C1PROD with CFR Federal Communications Commission § 73.23

White area. The area or population stations are not afforded protection which does not receive interference- and must protect all Class A and Class free primary service from an author- B operations during nighttime hours. ized AM station or does not receive a New Class D stations that had not been signal strength of at least 1 mV/m from previously licensed as Class B will not an authorized FM station. be authorized. (b) Regional Channel. A regional [47 FR 8587, Mar. 1, 1982, as amended at 47 FR 13164, Mar. 29, 1982; 47 FR 13812, Apr. 1, 1982; channel is one on which Class B and 50 FR 18821, May 2, 1985; 50 FR 47054, Nov. 14, Class D stations may operate and serve 1985; 56 FR 64856, Dec. 12, 1991; 62 FR 51058, primarily a principal center of popu- Sept. 30, 1997; 66 FR 20755, Apr. 25, 2001] lation and the rural area contiguous thereto. § 73.21 Classes of AM broadcast chan- nels and stations. NOTE: Until the North American Regional Agreement (NARBA) is termi- (a) Clear channel. A clear channel is nated with respect to the Bahama Islands one on which stations are assigned to and the Dominican Republic, radiation to- serve wide areas. These stations are ward those countries from a Class B station protected from objectionable inter- may not exceed the level that would be pro- ference within their primary service duced by an omnidirectional antenna with a areas and, depending on the class of transmitted power of 5 kW, or such lower station, their secondary service areas. level as will comply with NARBA require- ments for protection of stations in the Ba- Stations operating on these channels hama Islands and the Dominican Republic are classified as follows: against objectionable interference. (1) Class A station. A Class A station is an unlimited time station that oper- (c) Local channel. A local channel is ates on a clear channel and is designed one on which stations operate unlim- to render primary and secondary serv- ited time and serve primarily a com- ice over an extended area and at rel- munity and the suburban and rural atively long distances from its trans- areas immediately contiguous thereto. mitter. Its primary service area is pro- (1) Class C station. A Class C station is tected from objectionable interference a station operating on a local channel from other stations on the same and and is designed to render service only adjacent channels, and its secondary over a primary service area that may service area is protected from inter- be reduced as a consequence of inter- ference from other stations on the ference in accordance with § 73.182. The same channel. (See § 73.182). The oper- power shall not be less than 0.25 kW, ating power shall not be less than 10 nor more than 1 kW. Class C stations kW nor more than 50 kW. (Also see that are licensed to operate with 0.1 § 73.25(a)). kW may continue to do so. (2) Class B station. A Class B station [56 FR 64856, Dec. 12, 1991] is an unlimited time station which is designed to render service only over a § 73.23 AM broadcast station applica- primary service area. Class B stations tions affected by international are authorized to operate with a min- agreements. imum power of 0.25 kW (or, if less than (a) Except as provided in paragraph 0.25 kW, an equivalent RMS antenna (b) of this section, no application for an field of at least 141 mV/m at 1 km) and AM station will be accepted for filing if a maximum power of 50 kW, or 10 kW authorization of the facilities re- for stations that are authorized to op- quested would be inconsistent with erate in the 1605–1705 kHz band. international commitments of the (3) Class D station. A Class D station under treaties and other operates either daytime, limited time international agreements, arrange- or unlimited time with nighttime ments and understandings. (See list of power less than 0.25 kW and an equiva- such international instruments in lent RMS antenna field of less § 73.1650(b)). Any such application that than 141 mV/m at one km. Class D sta- is inadvertently accepted for filing will tions shall operate with daytime pow- be dismissed. ers not less than 0.25 kW nor more than (b) AM applications that involve con- 50 kW. Nighttime operations of Class D flicts only with the North American

13

VerDate Mar<15>2010 10:45 Nov 16, 2010 Jkt 220203 PO 00000 Frm 00023 Fmt 8010 Sfmt 8010 Y:\SGML\220203.XXX 220203 WReier-Aviles on DSKGBLS3C1PROD with CFR