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Converts between power ratios and decibel scale for audio, RF, and other applications. Logarithmic scale matches human perception.
Formel
dBm = 10 × log10(P ÷ 0.001)
- P
- P value — Variable used in the calculation
Trin-for-trin guide
- 1dBm = 10 × log10(P ÷ 0.001)
- 2dBW = 10 × log10(P)
- 3Reverse: power (watts) = 10^(dBm ÷ 10) ÷ 1000
- 4Every 3 dB ≈ 2× power
- 5Every 10 dB ≈ 10× power
Løste eksempler
Input
Power 1W
Resultat
30 dBm
Almindelige fejl at undgå
- ✕Confusing dBm (power) with dBV (voltage) with dBu (relative to 0.775V)
- ✕Adding dBm values instead of multiplying power
Ofte stillede spørgsmål
Why use decibels instead of watts?
Logarithmic scale compresses large ranges (1W to 1MW becomes 30 dBm to 60 dBm), easier comparison.
What's typical dBm for audio and RF?
Audio -20 to +4 dBu typical; WiFi transmit +17 to +30 dBm; cellular -30 to +33 dBm.
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