AUTHORITY: The provisions of this Part 73 issued under sec. 4 and 303, 48 Stat. 1066, as amended, 1082, as amended; 47 U.S.C. 154, 303. Interpret or apply secs. 301, 303, 307, 48 Stat. 1081, 1082, as amended, 1083, as amended, 47 U.S.C. 301, 303, 307. Other statutory and executive order provisions authorizing or interpreted or applied by specific sections are cited to text.

Subpart A-Standard Broadcast
Stations

SOURCE: The provisions of this Subpart A appear at 28 F.R. 13574, Dec. 14, 1963, unless otherwise noted.

§ 73.2

Standard broadcast band.

The term "standard broadcast band" means the band of frequencies extending from 535 to 1605 kc/s.

[33 F.R. 15417, Oct. 17, 1968]

§ 73.3 Standard broadcast channel.

The term "standard broadcast channel" means the band of frequencies occupied by the carrier and two side bands of a broadcast signal with the carrier frequency at the center. Channels shall be designated by their assigned carrier frequencies. The 107 carrier frequencies assigned to standard broadcast stations shall begin at 540 kc/s and be in successive steps of 10 kc/s.

[33 F.R. 15417, Oct. 17, 1968] § 73.4

Dominant station.

The term "dominant station" means a Class I station, as defined in § 73.21, operating on a clear channel.

§ 73.5 Secondary station.

The term "secondary station" means any station, except a Class I station, operating on a clear channel.

[33 F.R. 15417, Oct. 17, 1968]

§ 73.6 Daytime.

The term "daytime" means that period of time between local sunrise and local sunset.

§ 73.7 Nighttime.

The term "nighttime" means that period of time between local sunset and local sunrise.

[33 F.R. 4410, Mar. 12, 1968]

§ 73.8 Sunrise and sunset.

The terms "sunrise" and "sunset" mean, for each particular location and during any particular month, the time of sunrise and sunset as specified in the instrument of authorization. See § 73.83. [33 F.R. 4410, Mar. 12, 1968]

§ 73.9 Broadcast day.

The term "broadcast day" means that period of time between local sunrise and 12 midnight local time.

[33 F.R. 4410, Mar. 12, 1968]

§ 73.10 Experimental period.

The term "experimental period" means that time between 12 midnight local time and local sunrise. This period may be used for experimental purposes in testing and maintaining apparatus by the licensee of any standard broadcast station on its assigned frequency and with its authorized power, provided no interference is caused to other stations maintaining a regular operating schedule within such period. No station licensed for "daytime" or "specified hours" of operation may broadcast any regular or scheduled program during this period.

[28 F.R. 13574, Dec. 14, 1963, as amended at 33 F.R. 4410, Mar. 12, 1968]

§ 73.11 Service areas.

(a) The term "primary service area" of a broadcast station means the area in which the groundwave is not subject to objectionable interference or objectionable fading.

(b) The term "secondary service area" of a broadcast station means the area served by the skywave and not subject to objectionable interference. The signal

84-016-72-2

The term "portable transmitter" means a transmitter so constructed that it may be moved about conveniently from place to place, and is in fact so moved about from time to time, but not ordinarily used while in motion. In the standard broadcast band, such a transmitter is used in making field intensity measurements for locating a transmitter A site for a standard broadcast station. portable broadcast station will not be licensed in the standard broadcast band for regular transmission of programs intended to be received by the public. § 73.14 Technical definitions.

(a) Combined audio harmonics. The term "combined audio harmonics" means the arithmetical sum of the amplitudes of all the separate harmonic components. Root sum square harmonic readings may be accepted under conditions prescribed by the Commission.

(b) Effective field. The term "effective field" or "effective field intensity" is the root-mean-square (RMS) value of the inverse distance fields at a distance of 1 mile from the antenna in all directions in the horizontal plane.

(c) Nominal power. "Nominal power" is the power of a standard broadcast station, as specified in a system of classification which includes the following values; 50 kw., 25 kw., 10 kw., 5 kw., 1 kw., 0.5 kw., 0.25 kw.

(d) Operating power. Depending on the context within which it is employed, the term "operating power" may be synonomous with "nominal power" or "antenna power."

(e) Maximum rated carrier power. "Maximum rated carrier power" is the maximum power at which the transmitter can be operated satisfactorily and is determined by the design of the transmitter and the type and number of vacuum tubes used in the last radio stage.

(f) Plate input power. "Plate input power" means the product of the direct plate voltage applied to the tubes in the

last radio stage and the total direct current flowing to the plates of these tubes, measured without modulation.

(g) Antenna power. "Antenna input power" or "antenna power" means the product of the square of the antenna current and the antenna resistance at the point where the current is measured.

(h) Antenna current. “Antenna current" means the radio-frequency current in the antenna with no modulation.

(i) Antenna resistance. "Antenna resistance" means the total resistance of the transmitting antenna system at the operating frequency and at the point at which the antenna current is measured.

(j) Modulator stage. "Modulated stage" means the last amplifier stage of the modulating wave which modulates a radio-frequency stage.

(k) Modulated stage. "Modulated stage" means the radio-frequency stage to which the modulator is coupled and in which the continuous wave (carrier wave) is modulated in accordance with the system of modulation and the characteristics of the modulating wave.

(1) Last radio stage. "Last radio stage" means the oscillator or radio-frequency-power amplifier stage which supplies power to the antenna.

(m) Percentage modulation (amplitude):

In a positive direction: