"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"
dBa: Abbreviation for decibels adjusted. Weighted absolute noise power, calculated in dB referenced to 3.16 picowatts (-85 dBm), which is 0 dBa. Note: The use of F1A-line or
HA1-receiver weighting must be indicated in parentheses as required. A one-milliwatt, 1000-Hz tone will read +85 dBa, but the same power as white noise, randomly distributed
over a 3-kHz band (nominally 300 to 3300 Hz), will read +82 dBa, due to the frequency weighting. Synonym dBrn adjusted.
dBc: Abbreviation. dB relative to the carrier power.
Decibel: The standard unit used to express transmission gain or
loss and relative power levels. Also called dB.
Deflection: The displacement of an electron beam from its line of
sight path.
Demodulate: To recover the information originally impressed on
the radio wave.
Dielectric: A material that does not conduct electricity, such as
rubber or glass, i.e. an insulator.
Dielectric Antenna: -- Text in Review.
Diffraction: The process by which electromagnetic waves are bent
so that they appear behind an obstruction.
Dipole antenna: A center-fed wire antenna whose conductors are
in a straight line. Usually a straight, center-fed, one-half wavelength antenna.
Dipole Antenna
Directional antenna: An antenna designed to transmit and receive RF energy in a specific direction(s). An antenna that radiates most effectively in only one direction. An antenna in which the radiation pattern is not omnidirectional.
Direct waves: Waves which propagate in a straight line from the transmitting to the receiving antennas.
Directivity: The property of radiating more energy in some directions than in others.
Director: A conductor placed in front of a driven element to cause directivity.
Discone Antenna: Refer to biconical antenna.
| Dish Antenna: An antenna shaped like a dish. Same as a Parabolic Antenna. A similar graphic to the Humvee mounted Dish is a Towed Dish Antenna [towed antenna], same antenna on a different mount. A dish antenna with no fixed location. Also reference mobile antenna. |
 Dish Antenna |
Doublet: Another name for the dipole antenna.
Downlink: A data link from a satellite or other spacecraft to a terrestrial terminal. A data link from an airborne platform to a ground-based terminal.
Driven Array: An array in which all of the elements are driven.
Driven element: An element of an antenna (transmitting or receiving) that is connected directly to the transmission line.
Ducting: The propagation of VHF/UHF wave by bouncing between the Earths surface and the interface between layers of air having different dielectric constants.
Dummy Antenna. See Dummy Load
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