NationMaster - Encyclopedia: DBm

dBm is an abbreviation for the power ratio in decibel (dB) of the measured power referenced to one milliwatt (mW). It is used in radio, microwave and fiber optic networks as a convenient measure of absolute power because of its capability to express both very large and very small values in a short form. dBm (or dBmW) and dBW are independent of impedance (as opposed to dBV which is dependent, for example). Image File history File links Relationship_between_dBu_and_dBm. ... Image File history File links Relationship_between_dBu_and_dBm. ... The decibel is a dimensionless unit (like percent) that is a measure of ratios on a logarithmic scale. ... A voltage source is any device or system that produces an electromotive force between its terminals OR derives a secondary voltage from a primary source of the electromotive force. ... In physics, heat, symbolized by Q, is defined as energy in transit. ... Resistor symbols (US and Japan) Resistor symbols (Europe, IEC) A pack of resistors A resistor is a two-terminal electrical or electronic component that resists an electric current by producing a voltage drop between its terminals in accordance with Ohms law. ... The decibel (dB) is a measure of the ratio between two quantities, and is used in a wide variety of measurements in acoustics, physics and electronics. ... Milliwatt (SI symbol: mW) is a unit for measuring electrical power, equal to one-thousandth (10-3) of a watt. ... In physics, power (symbol: P) is the rate at which work is performed. ... The decibel (dB) is a measure of the ratio between two quantities, and is used in a wide variety of measurements in acoustics, physics and electronics. ...

Since it is referenced to the watt, it is an absolute unit, used when measuring absolute power. It should not be confused with dB, a dimensionless unit, which is used when measuring the ratio between two values, such as signal-to-noise ratio. The watt (symbol: W) is the SI derived unit of power, equal to one joule per second. ... In the physical sciences, a dimensionless number (or more precisely, a number with the dimensions of 1) is a quantity which describes a certain physical system and which is a pure number without any physical units; it does not change if one alters ones system of units of measurement... Signal-to-noise ratio (often abbreviated SNR or S/N) is an electrical engineering concept defined as the ratio of a given transmitted signal to the background noise of the transmission medium. ...

1 Unit conversions
2 See also
3 References
4 External links

Unit conversions

Zero dBm equals one milliwatt. A 3 dB increase represents roughly doubling the power, which means that 3 dBm equals roughly 2 mW. For a 3 dB decrease, the power is reduced by about one half, making −3 dBm equal to about 0.5 milliwatt. To express an arbitrary power P as x dBm, or go in the other direction, the equations

$x = 10 log_{10}(P / (P{_{1 mathrm{mW}})})$

and

$P =(P_{1 mathrm{mW}}) 10^{(x/10)}$ ,

respectively, should be used. Below is a table summarizing useful cases:

dBm level	Power	Notes
80 dBm	100 kW	Typical transmission power of FM radio station
60 dBm	1 kW = 1000 W	Typical RF power inside microwave oven
40 dBm	10 W
36 dBm	4 W	Typical maximum output power for Citizens' band radio stations (27MHz) in many countries
30 dBm	1 W = 1000 mW	Typical RF leakage from microwave oven
27 dBm	500 mW	Typical cellular phone transmission power
26 dBm	400 mW	Maximum output power for DCS 1800MHz mobile phone
25 dBm	316 mW
24 dBm	250 mW
23 dBm	200 mW
22 dBm	160 mW
21 dBm	125 mW	Maximum output from UMTS/3G Mobile Phone
20 dBm	100 mW	Bluetooth Class 1 radio, 100 m range (maximum output power from unlicensed FM transmitter)
15 dBm	32 mW
10 dBm	10 mW
5 dBm	3.2 mW
4 dBm	2.5 mW	Bluetooth Class 2 radio, 10 m range
3 dBm	2.0 mW
2 dBm	1.6 mW
1 dBm	1.3 mW
0 dBm	1.0 mW = 1000 µW	Bluetooth standard (Class 3) radio, 1 m range
−1 dBm	794 µW
−5 dBm	316 µW
−10 dBm	100 µW
−20 dBm	10 µW
−30 dBm	1.0 µW = 1000nW
−40 dBm	100 nW
−50 dBm	10 nW
−60 dBm	1.0 nW = 1000 pW
−70 dBm	100 pW	Average range (−60 to −80 dBm) of Wireless signal over a network
−80 dBm	10 pW
−111 dBm	0.008 pW	Thermal noise floor for commercial GPS signal bandwidth (2 MHz)
−127.5 dBm	0.000178 pW	Typical received signal power from GPS satellite
−174 dBm	0.000004 pW	Thermal noise floor for 1 Hz bandwidth
−∞ dBm	0.0 W

In United States Department of Defense practice, unweighted measurement is normally understood, applicable to a certain bandwidth, which must be stated or implied. FM radio is a broadcast technology invented by Edwin Howard Armstrong that uses frequency modulation to provide high-fidelity sound over broadcast radio. ... A typical CB base station. ... Microwave oven A microwave oven, or microwave, is a kitchen appliance employing microwave radiation primarily to cook or heat food. ... Cellular redirects here. ... Bluetooth logo Bluetooth is an industrial specification for wireless personal area networks (PANs). ... This article is concerned with low powered transmitters used in some countries for interfacing personal audio devices FM transmitter can also refer to high powered broadcast equipment used by pirate radio and licenced broadcast stations {{mergeto|FM transmitter (personal device)} The FM-transmitter plugs into an audio output (usually the... Johnsonâ€“Nyquist noise (thermal noise, Johnson noise, or Nyquist noise) is the noise generated by the thermal agitation of the charge carriers (the electrons) inside an electrical conductor in equilibrium, which happens regardless of any applied voltage. ... Over fifty GPS satellites such as this NAVSTAR have been launched since 1978. ... Johnson-Nyquist noise (sometimes thermal noise, Johnson noise or Nyquist noise) is the noise generated by the equilibrium fluctuations of the electric current inside an electrical conductor, which happens without any applied voltage, due to the random thermal motion of the charge carriers (the electrons). ... The United States Department of Defense, abbreviated as DoD or DOD and sometimes called the Defense Department, is a civilian Cabinet organization of the United States government. ... The A, B, C, and D weighting curves A weighting filter is used to emphasise some aspects of a phenomenon over others, for measurement or other purposes. ... This article or section does not cite its references or sources. ...

In European practice, psophometric weighting may be implied, as indicated by context; equivalent to dBm0p, which is preferred. World map showing Europe A satellite composite image of Europe Europe is one of the seven traditional continents of the Earth. ... Psophometric weighting refers to noise weighting as used especially in measuring noise on telecommunications circuits. ...

References

This article contains material from the Federal Standard 1037C (in support of MIL-STD-188), which, as a work of the United States Government, is in the public domain. Federal Standard 1037C entitled Telecommunications: Glossary of Telecommunication Terms is a U.S. Federal Standard, issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended. ... MIL-STD-188 is a series of U.S. military standards relating to telecommunications. ... A work of the United States Government is, as defined by United States copyright law, a work prepared by an officer or employee of the United States Government as part of that persons official duties. ... The public domain comprises the body of all creative works and other knowledge—writing, artwork, music, science, inventions, and others—in which no person or organization has any proprietary interest. ...

External links

Conversion: voltage V to dBm, dBu, and dBV

Categories: Federal Standard 1037C | MIL-STD-188 | Units of measure

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