1El decibel

Definicin El dB es la dcima parte de un Bel y

expresa ganancia o prdida de transmisin y niveles de potencias relativas.

dB=10 log (P2/P1)

P2: potencia medida P1: potencia de referencia

2Escala de ruidos y efectos que producen

Grfica de 10 log (P2/P1)

3Se observa que (1) Cada vez que la potencia se aumenta al

doble, la ganancia expresada en decibeles es de 3 dB.

Cada vez que la ganancia disminuye (prdida) en un factor de 2, la ganancia de potencia en decibeles disminuye (prdida) en aproximadamente 3 dB.

Se observa que (2) La potencia en decibeles aumenta en 10

dB cada vez que la ganancia de potencia se incrementa por un factor de 10.

Un resultado similar se obtiene cuando las ganancias de potencia son inferiores a la unidad (prdidas).

4dBm (dBmW), dBW, dBV, dBu ???Valores de referencia

Decibels (dB) = 10 log(P2/P1) dBm P1= 1 miliwatt a 600 ohms * dBW P1= 1 watt

Decibels (dB) = 20 log(V2/V1) dBV V1= 1 volt dBu V1= 0,775 volts * (1 miliwatt , 600 ohms)

Ejercicios Cul es el valor de tensin de una seal

de -15 dBV ? Cul es el valor de tensin de una seal

de 5 dBV ? Cul es el valor de tensin de una seal

de -6 dBu ? Cul es el valor de tensin de una seal

de 4 dBm ?

5

6Nivel operativo estandar (SOL)

1,55-1,95 V6-8 dBu (o dBm)

Broadcasting(emisiones de

radio)

1,23 V4 dBu (o dBm)

Profesional (estudio de grabacin)

0,32 V-10 dBVSemi-profesional/Audio

Hogareo

VoltdBContexto de operacin

Absolute measurements

Electric power dBm or dBmW

dB(1 mW) power measurement relative to 1 milliwatt. dBW

dB(1 W) same as dBm, with reference level of 1 watt. Electric voltage

dBu dB(0.775 V) (usually RMS) voltage amplitude referenced to

0.775 volt. Although dBu can be used with any impedance, dBu= dBm when the load is 600 . dBu is preferable, since dBv iseasily confused with dBV. The "u" comes from "unloaded".

dBV dB(1 V) (usually RMS) voltage amplitude of a signal in a

wire, relative to 1 volt, not related to any impedance.

7 Acoustics dB(SPL)

dB(Sound Pressure Level) relative to 20 micropascals (Pa) = 2105 Pa, the quietest sound a human can hear.[1] This isroughly the sound of a mosquito flying 3 metres away. This isoften abbreviated to just "dB", which gives some the erroneousnotion that "dB" is an absolute unit by itself.

Radio power dBm

dB(mW) power relative to 1 milliwatt. dB or dBu

dB(V/m) electric field strength relative to 1 microvolt permetre.

dBf D B(fW) power relative to 1 femtowatt.

dBW dB(W) power relative to 1 watt.

dBk dB(kW) power relative to 1 kilowatt.

Relative measurements dB(A), dB(B), and dB(C) weighting

These symbols are often used to denote the use of different frequency weightings, usedto approximate the human ear's response to sound, although the measurement is still in dB (SPL). Other variations that may be seen are dBA or dBA. According to ANSI standards, the preferred usage is to write LA = x dB, as dBA implies a reference to an"A" unit, not an A-weighting. They are still used commonly as a shorthand for A-weighted measurements, however.

dBd dB(dipole) the forward gain of an antenna compared to a half-wave dipole antenna.

dBi dB(isotropic) the forward gain of an antenna compared to an idealized isotropic

antenna. dBFS or dBfs

dB(full scale) the amplitude of a signal (usually audio) compared to the maximumwhich a device can handle before clipping occurs. In digital systems, 0 dBFS wouldequal the highest level (number) the processor is capable of representing. This is aninstantaneous (sample) value as compared to the dBm/dBu/dBv which are typicallyRMS.(Measured values are usually negative, since they should be less than themaximum.)

dBr dB(relative) simply a relative difference to something else, which is made apparent in

context. The difference of a filter's response to nominal levels, for instance. dBrn

dB above reference noise See also dBrnC. dBc

dB relative to carrier in telecommunications, this indicates the relative levels of noiseor sideband peak power, compared to the carrier power.

8Conclusin

Vistas las anteriores relaciones de tensiones en las expresiones de db, se podr realizar mediciones para calibrar nuestros equipos con la ayuda de un voltmetro.