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Power Attenuation
Calculate signal power loss and amplification
Attenuation
Power
About power attenuation
Attenuation: signal power decreases (positive dB).
Amplification: signal power increases (negative dB).
From dB to what is left
Attenuation in dB says how much power a signal loses on its way, in a cable, a connector, a filter or an attenuator. 3 dB leaves half the power, 10 dB a tenth, 20 dB a hundredth. A negative value is gain: more comes out than goes in, as behind an amplifier.
A(dB) = 10 · log₁₀(Pin / Pout)
loss(%) = (1 − 10−A / 10) × 100
loss(%) = (1 − 10−A / 10) × 100
Examples
3 dB: 49.9 % of the power is lost, and 1 W in gives 0.501 W out. 20 dB: 99 % is lost, and 1 W in gives 10 mW out.