decibels

[last updated: 2023-03-03]
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• For the ham exam:
  • Two things to know about decibels:
    • They are always a ratio of two things:
      for example: power-out / power-in
    • They are logarithmic.
      This means they are non-linear.

  • Things to memorize about decibles:
    • 3 dB is a 2x ratio
    • 1 dB is ~ 20%

  • Weirdnessess:
    • For Gain calcs, the ratio is out/in, so a quantity greater than 1
    • For Attenuation or Loss calcs, ...

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• Calculations:
  • Voltage:
  • Power:
    Gain _dB = 10 * log₁₀ (P_out / P_in )

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