Isotropic, a perfect POINT SOURCE, which radiates in a spherical manner. It defines a set of methods, variables and conventions that provide a consistent database interface independent of the actual database being used.
• Conversely, -10 dB will decrease the watt value to one tenth of that value: • (300 mW - 10dB ≈ 30 mW). dBI:-. • The unit of measurement dBi refers only to the gain of an antenna. The “i” stands for “isotropic”, which means that the change in power is referenced against an isotropic radiator.  In electromagnetics, an antenna's power gain or simply gain is a key performance figure which combines the antenna 's directivity and electrical efficiency. As a transmitting antenna, the figure describes how well the antenna converts input power into radio waves headed in a specified direction. The directive gain or directivity of an antenna in a given direction is the ratio of its radiation intensity in that direction to its mean radiation intensity. Yes, you will get more signal strength from a 7 dBI antenna than a 2.2dBI (specifically 4.8 dB). It solves that by radiating energy more directionally than an idea antenna that radiates evenly in all directions (0 dBI). This increased signal strength of 4.8 dB is 10^(4.8/10) = 3 times more power. Highly directional TV antenna and satellite dishes start range often from 16~24 dBi. Gain and beamwidth of peak direction are tradeoffs from isotropic. What this means to you is that when you are on the fringe, they can now aim to get 5dB more which is huge and that gets you into error free mode. dBi is decibels relative to isotropic radiator which means that the radiator (an antenna, usually) sends the signal equally strong in all directions, including above and below. Such a radiator would have 0 dBi. (I have yet to see an antenna like that -- it may exist only in math theory.).  The unit of antenna gain is dBi. dbI means Isotropic, a perfect POINT SOURCE, which radiates in a spherical manner. A perfect dipole radiates with a donut pattern, broadside to the long dimension of the dipole. It is a relative measurement to an ideal dipole that radiates in a perfect sphere The DBI is the standard database interface module for Perl. It defines a set of methods, variables and conventions that provide a consistent database interface independent of the actual database being used.  An alternative definition compares the antenna to the power received by a lossless half-wave dipole antenna, in which case the units are written as dBd. Since a lossless dipole antenna has a gain of 2.15 dBi, the relation between these units is: gain in dBd = gain in dBi - 2.15 dB. For a given frequency, the antenna's effective area is proportional to the power gain. The directive gain or directivity of an antenna in a given direction is the ratio of its radiation intensity in that direction to its mean radiation intensity. A letter following the dB indicates the reference antenna: * Gain specified in decibels-isotropic (dBi) indicates how the antenna performs as compared to an isotropic radiator. An isotropic radiator is a theoretical antenna that radiates equally in all directions (including up and down). * Gain specified in decibels-dipole (dBd) indicates how the antenna performs as compared to a dipole antenna. A dipole antenna has a 2.14 dBi gain over an isotropic radiator. Any dBi figure may be converted to dBd by subtracting 2.14. Be careful when comparing antenna gains that both values are in the same unit. Whip antenna gains are often specified in dBi, while other antennas are often specified in dBd. The decibel (dB) is a logarithmic unit used to express the ratio of two values of a physical quantity, often power or intensity. The number of decibels is ten times the logarithm to base 10 of the ratio of two power quantities, or of the ratio of the squares of two field amplitude quantities. One decibel is one tenth of one bel, named in honor of Alexander Graham Bell; however, the bel is seldom used. Antenna gain is usually defined as the ratio of the power produced by the antenna from a far-field source on the antenna's beam axis to the power produced by a hypothetical lossless isotropic antenna, which is equally sensitive to signals from all directions. The directive gain or directivity of an antenna in a given direction is the ratio of its radiation intensity in that direction to its mean radiation intensity.
https://supportforums.cisco.com/discussion/9173516/what-difference-between-db-dbi-and-dbm https://en.wikipedia.org/wiki/Antenna_gain http://electronics.stackexchange.com/questions/36031/does-higher-dbi-mean-further-range-for-an-antenna http://www.dslreports.com/faq/13008 http://www.dslreports.com/faq/2745 http://dbi.perl.org/ https://en.wikipedia.org/wiki/Antenna_gain https://answers.yahoo.com/question/index?qid=20070828174530AA8BQzt https://en.wikipedia.org/wiki/DBi https://en.wikipedia.org/wiki/Antenna_gain
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