Goto Section: 73.673 | 73.682 | Table of Contents
FCC 73.681
Revised as of October 1, 2007
Goto Year:2006 |
2008
Sec. 73.681 Definitions.
Amplitude modulation ( AM ). A system of modulation in which the envelope of
the transmitted wave contains a component similar to the wave form of the
signal to be transmitted.
Antenna electrical beam tilt. The shaping of the radiation pattern in the
vertical plane of a transmitting antenna by electrical means so that maximum
radiation occurs at an angle below the horizontal plane.
Antenna height above average terrain. The average of the antenna heights
above the terrain from approximately 3.2 (2 miles) to 16.1 kilometers (10
miles) from the antenna for the eight directions spaced evenly for each 45
degrees of azimuth starting with True North. (In general, a different
antenna height will be determined in each direction from the antenna. The
average of these various heights is considered the antenna height above the
average terrain. In some cases less than 8 directions may be used. See
Sec. 73.684(d)). Where circular or elliptical polarization is employed, the
antenna height above average terrain shall be based upon the height of the
radiation center of the antenna which transmits the horizontal component of
radiation.
Antenna mechanical beam tilt. The intentional installation of a transmitting
antenna so that its axis is not vertical, in order to change the normal
angle of maximum radiation in the vertical plane.
Antenna power gain. The square of the ratio of the root-mean-square free
space field strength produced at 1 kilometer in the horizontal plane, in
millivolts per meter for one kW antenna input power to 221.4 mV/m. This
ratio should be expressed in decibels (dB). (If specified for a particular
direction, antenna power gain is based on the field strength in that
direction only.)
Aspect ratio. The ratio of picture width to picture height as transmitted.
Aural center frequency. (1) The average frequency of the emitted wave when
modulated by a sinusoidal signal; (2) the frequency of the emitted wave
without modulation.
Aural transmitter. The radio equipment for the transmission of the aural
signal only.
Auxiliary facility. An auxiliary facility is an antenna separate a from the
main facility's antenna, permanently installed on the same tower or at a
different location, from which a 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).
BTSC. Broadcast Television systems committee recommendation for multichannel
television sound transmission and audio processing as defined in FCC
Bulletin OET 60.
Baseband. Aural transmitter input signals between 0 and 120 kHz.
Blanking level. The level of the signal during the blanking interval, except
the interval during the scanning synchronizing pulse and the chrominance
subcarrier synchronizing burst.
Chrominance. The colorimetric difference between any color and a reference
color of equal luminance, the reference color having a specific
chromaticity.
Chrominance subcarrier. The carrier which is modulated by the chrominance
information.
Color transmission. The transmission of color television signals which can
be reproduced with different values of hue, saturation, and luminance.
Effective radiated power. The product of the antenna input power and the
antenna power gain. This product should be expressed in kW and in dB above 1
kW (dBk). (If specified for a particular direction, effective radiated power
is based on the antenna power gain in that direction only. The licensed
effective radiated power is based on the maximum antenna power gain. When a
station is authorized to use a directional antenna or an antenna beam tilt,
the direction of the maximum effective radiated power will be specified.)
Where circular or elliptical polarization is employed, the term effective
radiated power is applied separately to the horizontally and vertically
polarized components of radiation. For assignment purposes, only the
effective radiated power authorized for the horizontally polarized component
will be considered.
Equivalent isotropically radiated power (EIRP). The term “equivalent
isotropically radiated power” (also known as “effective radiated power above
isotropic”) means the product of the antenna input power and the antenna
gain in a given direction relative to an isotropic antenna.
Field. Scanning through the picture area once in the chosen scanning
pattern. In the line interlaced scanning pattern of two to one, the scanning
of the alternate lines of the picture area once.
Frame. Scanning all of the picture area once. In the line interlaced
scanning pattern of two to one, a frame consists of two fields.
Free space field strength. The field strength that would exist at a point in
the absence of waves reflected from the earth or other reflecting objects.
Frequency departure. The amount of variation of a carrier frequency or
center frequency from its assigned value.
Frequency deviation. The peak difference between the instantaneous frequency
of the modulated wave and the carrier frequency.
Frequency modulation ( FM ). A system of modulation where the instantaneous
radio frequency varies in proportion to the instantaneous amplitude of the
modulating signal (amplitude of modulating signal to be measured after
pre-emphasis, if used) and the instantaneous radio frequency is independent
of the frequency of the modulating signal.
Frequency swing. The peak difference between the maximum and the minimum
values of the instantaneous frequency of the carrier wave during modulation.
Interlaced scanning. A scanning process in which successively scanned lines
are spaced an integral number of line widths, and in which the adjacent
lines are scanned during successive cycles of the field frequency.
IRE standard scale. A linear scale for measuring, in IRE units, the relative
amplitudes of the components of a television signal from a zero reference at
blanking level, with picture information falling in the positive, and
synchronizing information in the negative domain.
Note: When a carrier is amplitude modulated by a television signal in
accordance with Sec. 73.682, the relationship of the IRE standard scale to the
conventional measure of modulation is as follows:
Level IRE standard scale (units) Modulation percentage
Zero carrier 120 0
Reference white 100 12.5
Blanking 0 75
Synchronizing peaks (maximum carrier level) −40 100
Luminance. Luminous flux emitted, reflected, or transmitted per unit solid
angle per unit projected area of the source.
Main channel. The band of frequencies from 50 to 15,000 Hertz which
frequency modulate the main aural carrier.
Monochrome transmission. The transmission of television signals which can be
reproduced in gradations of a single color only.
Multichannel Television Sound (MTS). Any system of aural transmission that
utilizes aural baseband operation between 15 kHz and 120 kHz to convey
information or that encodes digital information in the video portion of the
television signal that is intended to be decoded as audio information.
Multiplex Transmission ( Aural ). A subchannel added to the regular aural
carrier of a television broadcast station by means of frequency modulated
subcarriers.
Negative transmission. Where a decrease in initial light intensity causes an
increase in the transmitted power.
Peak power. The power over a radio frequency cycle corresponding in
amplitude to synchronizing peaks.
Percentage modulation. As applied to frequency modulation, the ratio of the
actual frequency deviation to the frequency deviation defined as 100%
modulation expressed in percentage. For the aural transmitter of TV
broadcast stations, a frequency deviation of 25 kHz is defined as 100%
modulation.
Pilot subcarrier. A subcarrier used in the reception of TV stereophonic
aural or other subchannel broadcasts.
Polarization. The direction of the electric field as radiated from the
transmitting antenna.
Program related data signal. A signal, consisting of a series of pulses
representing data, which is transmitted simultaneously with and directly
related to the accompanying television program.
Reference black level. The level corresponding to the specified maximum
excursion of the luminance signal in the black direction.
Reference white level of the luminance signal. The level corresponding to
the specified maximum excursion of the luminance signal in the white
direction.
Scanning. The process of analyzing successively, according to a
predetermined method, the light values of picture elements constituting the
total picture area.
Scanning line. A single continuous narrow strip of the picture area
containing highlights, shadows, and half-tones, determined by the process of
scanning.
Standard television signal. A signal which conforms to the television
transmission standards.
Synchronization. The maintenance of one operation in step with another.
Television broadcast band. The frequencies in the band extending from 54 to
806 megahertz which are assignable to television broadcast stations. These
frequencies are 54 to 72 megahertz (channels 2 through 4), 76 to 88
megahertz (channels 5 and 6), 174 to 216 megahertz (channels 7 through 13),
and 470 to 806 megahertz (channels 14 through 69).
Television broadcast station. A station in the television broadcast band
transmitting simultaneous visual and aural signals intended to be received
by the general public.
Television channel. A band of frequencies 6 MHz wide in the television
broadcast band and designated either by number or by the extreme lower and
upper frequencies.
Television transmission standards. The standards which determine the
characteristics of a television signal as radiated by a television broadcast
station.
Television transmitter. The radio transmitter or transmitters for the
transmission of both visual and aural signals.
Vestigial sideband transmission. A system of transmission wherein one of the
generated sidebands is partially attenuated at the transmitter and radiated
only in part.
Visual carrier frequency. The frequency of the carrier which is modulated by
the picture information.
Visual transmitter. The radio equipment for the transmission of the visual
signal only.
Visual transmitter power. The peak power output when transmitting a standard
television signal.
[ 28 FR 13660 , Dec. 14, 1963, as amended at 35 FR 5692 , Apr. 8, 1970; 36 FR 5505 , Mar. 24, 1971; 36 FR 17429 , Aug. 31, 1971; 41 FR 56325 , Dec. 28, 1976;
42 FR 20823 , Apr. 22, 1977; 44 FR 36039 , June 20, 1979; 47 FR 35990 , Aug.
18, 1982; 49 FR 18106 , Apr. 27, 1984; 49 FR 38131 , Sept. 27, 1984; 49 FR 50048 , Dec. 26, 1984; 50 FR 23699 , June 5, 1985; 51 FR 12616 , Apr. 14, 1986;
56 FR 49707 , Oct. 1, 1991; 58 FR 44951 , Aug. 25, 1993; 62 FR 51059 , Sept.
30, 1997]
Goto Section: 73.673 | 73.682
Goto Year: 2006 |
2008
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