"A",
"B",
"C",
"D",
"E",
"F",
"G"/"H",
"I"/"J"/"K"/"L",
"M"/"N"/"O",
"P"/"Q",
"R",
"S",
"T",
"U"/"V"/"W"/"X"/"Y"/"Z"
Absolute gain: Of an antenna, for a given direction and polarization, the ratio of (a) the power that would be required at the input of an ideal isotropic radiator to (b) the power
actually supplied to the given antenna, to produce the same radiation intensity in the far-field region. Note 1: If no direction is given, the absolute gain of an antenna corresponds to
the direction of maximum effective radiated power. Note 2: Absolute gain is usually expressed in dB. Synonym isotropic gain. Of a device, the ratio of (a) the signal level at the
output of the device to (b) that of its input under a specified set of operating conditions. Note 1: Examples of absolute gain are no-load gain, full-load gain, and small-signal gain.
Note 2: Absolute gain is usually expressed in dB.
Absorption: In the transmission of electrical, electromagnetic, or acoustic signals, the conversion of the transmitted energy into another form, usually thermal. Note 1:
Absorption is one cause of signal attenuation. Note 2: The conversion takes place as a result of interaction between the incident energy and the material medium, at the molecular or
atomic level.
Absorption loss: That part of the transmission loss caused by the dissipation or conversion of electrical, electromagnetic, or acoustic energy into other forms of energy as a result of its interaction with a material medium.
Acceptance pattern: Of an antenna, for a given plane, a distribution plot of the off-axis power relative to the on-axis power as a function of angle or position. Note:
The acceptance pattern is the equivalent of a horizontal or vertical antenna pattern. Of an optical fiber or fiber bundle, a curve of total transmitted power plotted against the launch angle.
Adcock Antenna: An antenna array consisting of four equidistant vertical elements which can be used to transmit or receive directional radio waves.
Aerial cable: A communications cable designed for installation on, or suspension from, a pole or other overhead structure.
Altazimuth mount: A mounting, for a directional antenna or telescope, in which slewing takes place in (a) the plane tangent to the surface of the Earth or other frame of reference and (b)
elevation about, i.e., above or below, that plane. Synonym x-y mount. {alt-azimuth mount}
Alternating current: [AC] Current that is continually changing in magnitude
and periodically in direction from a zero reference level.
Amplification: The process of increasing the strength (current,
voltage, or power) of a signal.
Amplifier: An electronic component that boosts the voltage or power level of a signal that is a linear replica of the input signal, but with greater power or voltage level, and
sometimes with an impedance transformation. The output may also be a nonlinear analog function of the input signal, as in a signal compression device. Also See fiber amplifier,
optical repeater. Amplifier Manufacturers
Amplitude: The level of an audio or other signal in voltage or current.
The magnitude of variation in a changing quantity from its zero value.
Amplitude modulation: Modulation in which the amplitude of the
carrier wave is varied above and below its normal value in accordance
with the intelligence of the signal being transmitted. Also
called AM.
AM Modulation Waveform
Angle of incidence: The acute angle (smaller angle) at which a
wave of energy strikes an object or penetrates a layer of the atmosphere
or ionosphere.
Anisotropic: .The property of a radiator that allows it to emit strong radiation in one direction.
| Antenna: A device used to radiate or receive waves [electromagnetic energy] through space, generally RF energy. A conductor or set of conductors used to radiate RF energy into space or to collect RF energy from space or to do both. Antenna Manufacturers. |
 TV Antenna |
Antenna Array: A grouping of antennas. See graphic to the right. An assembly of antenna elements with dimensions, spacing, and illumination sequence such that the fields for the individual elements combine to produce a maximum intensity in a particular direction and minimum field intensities in other directions. Also refer to Phased Array Antenna
Antenna bandwidth: The frequency range over which a given antenna will accept signals.
Antenna Coupler: A device used for impedance matching between an antenna and a transmitter or receiver.
Antenna Efficiency: The ratio of the total radiated power to the total input power.
Antenna feed: Means by which power is transferred to and from the antenna and the connecting transmission line.
Antenna gain: The effectiveness of a directional antenna as compared to a standard non-direction antenna. It is usually expressed as the ratio in decibels of standard antenna input power to directional antenna input power that will produce the same field strength in the desired direction. For a receiving antenna, the ratio of signal power values produced at the receiver input terminals is used. The more directional an antenna is, the higher is its gain.
Antenna Lobe: A three-dimensional section of the radiation pattern of a directional antenna, bounded by one or more cones of nulls or by regions of diminished irradiance.
Antenna Matching: The process of adjusting impedance so that the input impedance of an antenna equals or approximates the characteristic impedance of its transmission line over a specified range of frequencies.
Antenna Tower: Any type of antenna placed atop a tower, which is used to rise the antenna above the ground. Also refer to manufacturers of Antenna Towers [includes a graphic of a UHF antenna tower].
Next section of "A" Terms and definitions
