| Definition: | quotient, usually expressed in logarithmic units, of the absolute gain G of an antenna to its noise temperature T referred to the antenna terminals at a specified frequency and in specified conditions of installation and operation
Note 1 to entry: If the noise temperature is expressed in kelvins and the gain as a power ratio, the quantity 10 log G/T is expressed in a unit designated by the symbol dB (K−1), sometimes written incorrectly dBK.
Note 2 to entry: In English, the term "figure of merit" has different meanings in relation to antenna receiving systems (see IEV 712-02-56), transductors (see IEV 431-02-15) and piezoelectric and dielectric resonators (see IEV 561-01-26).
Note 3 to entry: In French, the term "facteur de qualité" has a different meaning for a two-terminal element or circuit (see IEV 151-15-45), for a resonant circuit (see IEV 151-15-46), for radiation protection purposes (see IEV 395-01-39), in relation to antenna receiving systems (see IEV 712-02-56), and in radiology (see IEV 881-14-03).
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