Which unit measures the power of a radio signal with reference to 1 milliwatt?

Question

Options

• AdBw
• BdBm
• CmW
• DdBi

• A
  8% (2)
• B
  85% (22)
• C
  4% (1)
• D
  4% (1)

Explanation

dBm (decibel-milliwatt) is the unit that measures signal power relative to a reference point of 1 milliwatt, making it the standard unit used in RF (radio frequency) and wireless communications to express transmit power and signal strength. A reading of 0 dBm equals exactly 1 mW, with positive values indicating power greater than 1 mW and negative values indicating power less than 1 mW.

The other options are incorrect for the following reasons:

• dBw measures power relative to 1 watt (not 1 milliwatt), making it 30 dB higher than the equivalent dBm value
• mW (milliwatts) is simply a linear unit of power measurement, not a logarithmic decibel-based measurement
• dBi measures antenna gain relative to an isotropic radiator, and has nothing to do with signal power levels

Memory tip: The "m" in dBm stands for milliwatt - just remember that the suffix after "dB" tells you the reference unit. If you see dBm, think "decibels referenced to a milliwatt." This pattern also helps you remember dBw = decibels referenced to a watt.

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