EIRP - Abbreviation for Effective-Isotropic-Radiated-Power
Effective Isotropic Radiated Power is the apparent power transmitted towards the receiver, if it is assumed that the signal is radiated equally in all directions, such as a spherical wave emanating from a point source; in other words, the arithmetic product of the power supplied to an antenna and its gain.
EIRP = G * P = 10(g/10) * P [W]
G: Antenna gain coefficient
g: Antenna gain [dBi]
P: Power [W]
Following table contains values for the C band. The values shown in the table assume having an LNB with noise figure of 20°K: