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field strength to dBm

Field Strength to dBm Calculator

This calculator converts Electric Field Strength (also known as Field Intensity) to Power.

The unit for field strength is V/m and power is measured in dBm or Watt.

The calculator requires as input

  • Field Strength (E)
  • Antenna gain (G)
  • Frequency of operation

It uses this to compute the Antenna Factor, RMS voltage and then power in dBm.

Formula

AF = 20*Log10(9.73/(λ√G))

V = E/10(AF/20)

Background

The field strength or intensity is specified at a point in space. Note that it cannot simply be converted from V/m to Volt. Instead the antenna factor associated with the antenna used to receive the signal is used to convert it to an equivalent voltage at the input to the receiver using the second formula above. The RMS voltage is converted to power in dBm.