DBm
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- The title of this article is incorrect because of technical limitations. The correct title is dBm.
dBm is an abbreviation for the power ratio in dB (decibel) of the measured power referenced to one milliwatt.
The term dB is mainly used for an attenuation or an amplification, but dBm for a measured power.
Note 1: dBm is used in communication work as a measure of absolute power values. Zero dBm equals one milliwatt. A 3 dBm increase represents roughly doubling the power, which means that 3 dBm equals 2 milliwatt. For a 3 dBm decrease the power is reduced by one half, making -3 dBm equal to 0.5 milliwatt. To express an arbitrary power <math>P<math> as <math>x \, \mathrm{dBm}<math>, or go in the other direction, the equations <math>x = 10 \log_{10}(P / (1 \, \mathrm{mW}))<math> and <math>P =(1 \, \mathrm{mW}) 10^{(x/10)}<math>, respectively, should be used. Below is table summarizing useful cases:
| 40 dBm | 10 watts |
| 36 dBm | 4 watts |
| 30 dBm | 1 watt |
| 27 dBm | 500 milliwatts |
| 26 dBm | 400 milliwatts |
| 25 dBm | 320 milliwatts |
| 24 dBm | 250 milliwatts |
| 23 dBm | 200 milliwatts |
| 22 dBm | 160 milliwatts |
| 21 dBm | 130 milliwatts |
| 20 dBm | 100 milliwatts |
| 15 dBm | 32 milliwatts |
| 10 dBm | 10 milliwatts |
| 5 dBm | 3.2 milliwatts |
| 4 dBm | 2.5 milliwatts |
| 3 dBm | 2.0 milliwatts |
| 2 dBm | 1.6 milliwatts |
| 1 dBm | 1.3 milliwatts |
| 0 dBm | 1.0 milliwatts |
| -1 dBm | 0.79 milliwatts |
| -5 dBm | 0.32 milliwatts |
| -10 dBm | 0.1 milliwatts |
| -20 dBm | 0.01 milliwatts |
| -30 dBm | 0.001 milliwatts |
| -40 dBm | 0.0001 milliwatts |
| -50 dBm | 0.00001 milliwatts |
| -60 dBm | 0.000001 milliwatts |
| -70 dBm | 0.0000001 milliwatts |
| -80 dBm | 0.00000001 milliwatts |
Note 2: In DOD practice, unweighted measurement is normally understood, applicable to a certain bandwidth, which must be stated or implied.
Note 3: In European practice, psophometric weighting may be implied, as indicated by context; equivalent to dBm0p, which is preferred.
See also
Zero dBm transmission level point