PPT Slide

Decibels*

• decibel is a measure of the difference in two power levels:

  db = 10 log 10 (P1 / P2) (note P = V2 / R)
  

• eg if 10 mW sent and 5 mW received then

  loss in db = 10 log (5/10) = 10 ( -0.3 ) = -3 db
  

• 3 db is a factor of two change in power level

• eg if 700 watts becomes 175 watts its a 6 db loss

• dbW is referenced to 1 watt, ie

  Power in dbW = 10 log (p1 / 1 watt)
  

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