Decibel watt

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The decibel watt or dBW is a unit for the measurement of the strength of a signal expressed in decibels relative to one watt. It is used because of its capability to express both very large and very small values of power in a short range of number; e.g., 1 milliwatt = −30 dBW, 1 watt = 0 dBW, 10 watts = 10 dBW, 100 watts = 20 dBW, and 1,000,000 W = 60 dBW.

\mbox{Power in dBW} = 10 \log_{10}\frac{\mbox{Power in W}}{ 1 \mathrm{W}}

Compare to dBm, which is referenced to one milliwatt (0.001 W). Certain dBW value in dBm is always 30 more because 1 watt is 1,000 milliwatts, and ratio of 1,000 (in power) is 30 dB; e.g., 10 dBm (10 mW) is equal to −20 dBW (0.01 W).

Although the decibel (dB) is permitted for use alongside SI units, the dBW is not.

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