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RF Power Units and Conversions

A practical guide to watts, dBm, power ratios, and decibels, focused on building intuition for logarithmic RF units before you try to read a link budget or a bench measurement.

Key formulas

Watts to dBm
dBm = 10 log10(P / 1 mW)
Power ratio to dB
dB = 10 log10(P2 / P1)

Why logarithmic units help

RF systems often involve gains and losses across large ranges of power. Decibels make those changes easier to compare and combine than raw linear power values.

Once you understand the unit conversions, link budgets and received-power calculations become far easier to follow.

Common mistakes

  • Using 20 log10 where 10 log10 is required for power ratios.
  • Treating dB as an absolute power unit instead of a relative ratio.
  • Mixing dBm and dB in the same expression without tracking what each one represents.
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