Decibel (dB)
The decibel explained: why it is logarithmic, the difference between the power and amplitude formulas, and what dBm and dBW actually reference.
Questions people ask
Why is 3 dB called the half-power point?
Because 10 log₁₀(0.5) is −3.01 dB. A filter's cutoff frequency is defined where output power has fallen to half its passband value.
What is the difference between dB and dBm?
dB is a bare ratio; dBm is referenced to one milliwatt. 30 dBm is 1 W, and a 3 dB gain takes 30 dBm to 33 dBm — which is 2 W.
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Last updated 22 August 2026