Mobility Hero Tutorials

There are many different ways to look at power and the amount used. There are also relative and absolute measurements. Relative compares to a similar measurement method while absolute measures are an exact representation.

Relative Measurements include dB (decibel), dBi (decibels isotropic), and dBd (decibel dipole).

·         Decibels are a relative measurement and are used for comparison. Decibels measure the difference in power between a transmitting device and a receiving device. Example: the antenna cable introduces a power loss of 3 dB. Also 3 dBs is expressing the change in power. The absolute power difference between 3 and 6 dBm is not the same as 6 and 9. But the relative power difference between the two examples is both 3dB.

·         dBi is gain of decibels compared against a theoretical isotropic radiator. Used to assess the gain of an antenna

Example: This antenna increases power by 3 dBi

·         dBd is compared to a dipole antenna. The decibels gains in relation to a dipole antenna are expressed in dBd.

Absolute Measurements include W (watt), mW (milliwatt), and dBm (decibel-milliwatt)

·         Watts are basic units of power and are calculated by multiplying volts times amps

·         Milliwatts are 1/1000 of a watt. They are the most common measurement in wireless networking and transmit power which is regulated by the FCC.

·         dBm is different in the fact it is comparing values like the relative measurements but, it is comparing known values so that makes it an absolute  unit of power. dBm compare the signal to an absolute unit, signal relative to 1 mW. 0 dBm = 1mW. When talking about received signal strength one usually uses dBm

dBm to mW conversion table