Question 1

Why is there a factor of 10 vs 20 in dB formulas?

Accepted Answer

Power uses 10× because dB was defined for power ratios. Voltage/current uses 20× because P = V²/R, so power ratio = voltage ratio squared. Log of square = 2× log.

Question 2

What does negative dB mean?

Accepted Answer

Negative dB indicates attenuation (signal loss). -3 dB means half the power, -6 dB means quarter power. Negative values mean the output is smaller than input.

Question 3

What is the difference between dB and dBm?

Accepted Answer

dB is a ratio (unitless). dBm is absolute power relative to 1 milliwatt. 0 dBm = 1 mW, +10 dBm = 10 mW, +30 dBm = 1 W.

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