EIRP (Effective Isotropic Radiated Power) is the actual amount of signal leaving the antenna and is a value measured in db and is based on 3 values:
Transmit Power (dBm)
Cable Loss (dB)
Antenna Gain (dBi)
The dB measures the power of a signal as a function of its ratio to another standardized value. The abbreviation dB is often combined with other abbreviations in
order to represent the values that are compared. Here are two examples:
dBm --The dB value is compared to 1 mW.
dBw --The dB value is compared to 1 W.
You can calculate the power in dBs from this formula:
Power (in dB) = 10 * log10 (Signal/Reference)
This list defines the terms in the formula:
log10 is logarithm base 10.
Signal is the power of the signal (for example, 50 mW). Reference is the reference power (for example, 1 mW).
How to find EIRP
To determine EIRP follow this equation:
[Transmit Power] - Cable Loss + Antenna Gain = EIRP