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The electric field strength at a specific point can be determined from the power delivered to the transmitting antenna, its geometry and radiation resistance. Consider the case of a center-fed half-wave dipole antenna in free space, where the total length L is equal to one half wavelength (λ/2).
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 phrase "dB below full scale" has appeared in print since the 1950s, [27] [28] [29] and the term "dBFS" has been used since 1977. [30]Although the decibel (dB) is permitted for use alongside units of the International System of Units (SI), the dBFS is not.
Modern audio equipment does not use 600 Ω matched loads, hence dBm unloaded (dBu). The most common nominal level for professional equipment is +4 dBu (by convention, decibel values are written with an explicit sign symbol). For consumer equipment it is −10 dBV, which is used to reduce manufacturing costs. [3]
Minimum terrestrial digital-TV RF antenna signal (−85 dBm over 75 Ω) [4] [5] 56 μV Minimum terrestrial analog-TV RF antenna signal (35 dB[μV]) [6] [7] [8] 10 −4: 500–1000 μV Miniature endplate potentials, spontaneous fluctuations in neuron potentials [1] 10 −3: 1–2 mV Potential created at ambient temperatures from K Type ...
A velocity prediction program (VPP) is a computer program which solves for the performance of a sailing yacht in various wind conditions by balancing hull and sail forces. VPPs are used by yacht designers, boat builders, model testers, sailors, sailmakers, also America's Cup teams, to predict the performance of a sailboat before it has been built or prior to major modifications.
7 dBm tech: laser in a CD-ROM drive 5–10 × 10 −3: 7 dBm to 10 dBm tech: laser in a DVD player: 10 −2: centi-(cW) 7 × 10 −2: 18 dBm tech: antenna power in a typical consumer wireless router: 10 −1: deci-(dW) 1.2 × 10 −1: 21 dBm astro: total proton decay power of Earth, assuming the half life of protons to take on the value 10 35 ...
A power level of 0 dBm corresponds to one milliwatt, and 1 dBm is one decibel greater (about 1.259 mW). In professional audio specifications, a popular unit is the dBu . This is relative to the root mean square voltage which delivers 1 mW (0 dBm) into a 600-ohm resistor, or √ 1 mW × 600 Ω ≈ 0.775 V RMS .