The Decibel (dB) is a logarithmic unit used to describe a ratio. In radio communication, dB expresses the signal level, or power as it relates to measurable Watts, milliwatts or microvolts and may be expressed in Watts as W, Decibel milliwatt as dBm, Decibel Watt as dBw, and on occasion as Decibel microvolt dBµV.

     Each 3 dB increment up represents double the power level, and each 3 dB decrease is half of the power. In this way, extremely low signal levels are measured.

     Decibel levels expressed as a negative number (ex. -119 dBm) signify a lower signal level. A receiver with a greater negative dB number is more sensitive, while a transmitter with a higher Decibel level is more powerful.

     Received signal strengths are usually measured in dBm, and transmitter powers are generally expressed in Watts. Antenna dBi is added or subtracted to signal dBm and dB line and insertion losses.