Effective radiated power of an antenna at a distance R?

Question

Equation for effecitive radiated power of an antenna at a distance R

Answer 1

Can’t tell. You need to specify the antenna type or its radiated pattern (such as isotropic i.e. equal in all spherical direction, 120-deg sectorized down-tilted cellular, etc…)

In general, the RF industry uses two superimposed models to estimate the receiver field strength: (1) an antenna gain parameter in the direction of interest, call dBi (something similar to decibel referenced a perfect isotropic radiation), and (2) the path loss factor which is proportional to the distance raised to a power of between 2 and 4 depending on the wavelength and the air environment conditions.