Search results
Results from the WOW.Com Content Network
dBm or dB mW (decibel-milliwatts) is a unit of power level expressed using a logarithmic decibel (dB) scale respective to one milliwatt (mW). It is commonly used by radio, microwave and fiber-optical communication technicians & engineers to measure the power of system transmissions on a log scale , which can express both very large and very ...
The decibel originates from methods used to quantify signal loss in telegraph and telephone circuits. Until the mid-1920s, the unit for loss was miles of standard cable (MSC). 1 MSC corresponded to the loss of power over one mile (approximately 1.6 km) of standard telephone cable at a frequency of 5000 radians per second (795.8 Hz), and matched closely the smallest attenuation detectable to a ...
The decibel watt (dBW or dB W) 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.
Received power (dBm) = transmitted power (dBm) + gains (dB) − losses (dB) Power levels are expressed in ( dBm ), Power gains and losses are expressed in decibels (dB), which is a logarithmic measurement, so adding decibels is equivalent to multiplying the actual power ratios.
Decibels relative to full scale (dBFS or dB FS) is a unit of measurement for amplitude levels in digital systems, such as pulse-code modulation (PCM), which have a defined maximum peak level. The unit is similar to the units dBov and decibels relative to overload ( dBO ).
The symbol dBrn or dB(rn) is an abbreviation for decibels above reference noise.. Weighted noise power in dB is referred to 1.0 picowatt.Thus, 0 dBrn = -90 dBm.Use of 144 line, 144-receiver, or C-message weighting, or flat weighting, can be indicated in parentheses.
High-powered transmissions, such as those used in broadcasting, are expressed in dB-millivolts per metre (dBmV/m). For very low-power systems, such as mobile phones , signal strength is usually expressed in dB - microvolts per metre (dBμV/m) or in decibels above a reference level of one milliwatt ( dBm ).
This is more commonly used than scalar linear gain and a positive quantity is normally understood as simply a "gain", while a negative quantity is a "negative gain" (a "loss"), equivalent to its magnitude in dB. For example, at 100 MHz, a 10 m length of cable may have a gain of −1 dB, equal to a loss of 1 dB.