Goto Section: 73.1 | 73.21 | Table of Contents
FCC 73.14
Revised as of October 1, 2008
Goto Year:2007 |
2009
Sec. 73.14 AM broadcast definitions.
AM broadcast band. The band of frequencies extending from 535 to 1705 kHz.
AM broadcast channel. The band of frequencies occupied by the carrier and
the upper and lower sidebands of an AM broadcast signal with the carrier
frequency at the center. Channels are designated by their assigned carrier
frequencies. The 117 carrier frequencies assigned to AM broadcast stations
begin at 540 kHz and progress in 10 kHz steps to 1700 kHz. (See Sec. 73.21 for
the classification of AM broadcast channels).
AM broadcast station. A broadcast station licensed for the dissemination of
radio communications intended to be received by the public and operated on a
channel in the AM broadcast band.
Amplitude modulated stage. The radio-frequency stage to which the modulator
is coupled and in which the carrier wave is modulated in accordance with the
system of amplitude modulation and the characteristics of the modulating
wave.
Amplitude modulator stage. The last amplifier stage of the modulating wave
amplitude modulates a radio-frequency stage.
Antenna current. The radio-frequency current in the antenna with no
modulation.
Antenna input power. The product of the square of the antenna current and
the antenna resistance at the point where the current is measured.
Antenna resistance. The total resistance of the transmitting antenna system
at the operating frequency and at the point at which the antenna current is
measured.
Auxiliary facility. An auxiliary facility is an AM antenna tower(s) separate
from the main facility's antenna tower(s), permanently installed at the same
site or at a different location, from which an AM station may broadcast for
short periods without prior Commission authorization or notice to the
Commission while the main facility is not in operation (e.g., where tower
work necessitates turning off the main antenna or where lightning has caused
damage to the main antenna or transmission system) ( See Sec. 73.1675).
Blanketing. The interference which is caused by the presence of an AM
broadcast signal of one volt per meter (V/m) or greater strengths in the
area adjacent to the antenna of the transmitting station. The 1 V/m contour
is referred to as the blanket contour and the area within this contour is
referred to as the blanket area.
Carrier-amplitude regulation (Carrier shift). The change in amplitude of the
carrier wave in an amplitude-modulated transmitter when modulation is
applied under conditions of symmetrical modulation.
Combined audio harmonics. 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 FCC.
Critical hours. The two hour period immediately following local sunrise and
the two hour period immediately preceding local sunset.
Daytime. The period of time between local sunrise and local sunset.
Effective field; Effective field strength. The root-mean-square (RMS) value
of the inverse distance fields at a distance of 1 kilometer from the antenna
in all directions in the horizontal plane. The term “field strength” is
synonymous with the term “field intensity” as contained elsewhere in this
Part.
Equipment performance measurements. The measurements performed to determine
the overall performance characteristics of a broadcast transmission system
from point of program origination at main studio to sampling of signal as
radiated. (See Sec. 73.1590)
Experimental period. the time between 12 midnight local time and local
sunrise, used by AM stations for tests, maintenance and experimentation.
Frequency departure. The amount of variation of a carrier frequency or
center frequency from its assigned value.
Incidental phase modulation. The peak phase deviation (in radians) resulting
from the process of amplitude modulation.
Input power. Means the product of the direct voltage applied to the last
radio stage and the total direct current flowing to the last radio stage,
measured without modulation.
Intermittent service area. Means the area receiving service from the
groundwave of a broadcast station but beyond the primary service area and
subject to some interference and fading.
Last radio stage. The radio-frequency power amplifier stage which supplies
power to the antenna.
Left (or right) signal. The electrical output of a microphone or combination
of microphones placed so as to convey the intensity, time, and location of
sounds originated predominately to the listener's left (or right) of the
center of the performing area.
Left (or right) stereophonic channel. The left (or right) signal as
electrically reproduced in reception of AM stereophonic broadcasts.
Main channel. The band of audio frequencies from 50 to 10,000 Hz which
amplitude modulates the carrier.
Maximum percentage of modulation. The greatest percentage of modulation that
may be obtained by a transmitter without producing in its output, harmonics
of the modulating frequency in excess of those permitted by these
regulations. (See Sec. 73.1570)
Maximum rated carrier power. 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 or other amplifier
devices used in the last radio stage.
Model I facility. A station operating in the 1605–1705 kHz band featuring
fulltime operation with stereo, competitive technical quality, 10 kW daytime
power, 1 kW nighttime power, non-directional antenna (or a simple
directional antenna system), and separated by 400–800 km from other
co-channel stations.
Model II facility. A station operating in the 535–1605 kHz band featuring
fulltime operation, competitive technical quality, wide area daytime
coverage with nighttime coverage at least 15% of the daytime coverage.
Nighttime. The period of time between local sunset and local sunrise.
Nominal power. The antenna input power less any power loss through a
dissipative network and, for directional antennas, without consideration of
adjustments specified in paragraphs (b)(1) and (b)(2) of Sec. 73.51 of the
rules. However, for AM broadcast applications granted or filed before June
3, 1985, nominal power is specified in a system of classifications which
include the following values: 50 kW, 25 kW, 10 kW, 5 kW, 2.5 kW, 1 kW, 0.5
kW, and 0.25 kW. The specified nominal power for any station in this group
of stations will be retained until action is taken on or after June 3, 1985,
which involves a change in the technical facilities of the station.
Percentage modulation (amplitude)
In a positive direction:
M = MAX−C × 100
————––—––—
c
In a negative direction:
M = C−MIN × 100
————–—––—
c
Where:
M = Modulation level in percent.
MAX = Instantaneous maximum level of the modulated radio frequency envelope.
MIN = Instantaneous minimum level of the modulated radio frequency envelope.
C = (Carrier) level of radio frequency envelope without modulation.
Plate modulation. The modulation produced by introduction of the modulating
wave into the plate circuit of any tube in which the carrier frequency wave
is present.
Primary service area. Means the service area of a broadcast station in which
the groundwave is not subject to objectionable interference or objectionable
fading.
Proof of performance measurements or antenna proof of performance
measurements. The measurements of field strengths made to determine the
radiation pattern or characteristics of an AM directional antenna system.
Secondary service area. Means the service area of a broadcast station served
by the skywave and not subject to objectionable interference and in which
the signal is subject to intermittent variations in strength.
Stereophonic channel. The band of audio frequencies from 50 to 10,000 Hz
containing the stereophonic information which modulates the radio frequency
carrier.
Stereophonic crosstalk. An undesired signal occurring in the main channel
from modulation of the stereophonic channel or that occurring in the
stereophonic channel from modulation of the main channel.
Stereophonic pilot tone. An audio tone of fixed or variable frequency
modulating the carrier during the transmission of stereophonic programs.
Stereophonic separation. The ratio of the electrical signal caused in the
right (or left) stereophonic channel to the electrical signal caused in the
left (or right) stereophonic channel by the transmission of only a right (or
left) signal.
Sunrise and sunset. For each particular location and during any particular
month, the time of sunrise and sunset as specified in the instrument of
authorization (See Sec. 73.1209).
White area. The area or population which does not receive interference-free
primary service from an authorized AM station or does not receive a signal
strength of at least 1 mV/m from an authorized FM station.
[ 47 FR 8587 , Mar. 1, 1982, as amended at 47 FR 13164 , Mar. 29, 1982; 47 FR 13812 , Apr. 1, 1982; 50 FR 18821 , May 2, 1985; 50 FR 47054 , Nov. 14, 1985;
56 FR 64856 , Dec. 12, 1991; 62 FR 51058 , Sept. 30, 1997; 66 FR 20755 , Apr.
25, 2001]
Goto Section: 73.1 | 73.21
Goto Year: 2007 |
2009
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