For a microwave communication link, use this app to determine the radiation...
This app can be used to find the power density in the main beam of the antenna. The user is prompted to enter the gain of a tower-mounted antenna in dB, the transmitter power in Watts and the distance from the antenna in meters.
As an example, enter gain = 40.0, P = 5.0 and R = 20.0 then push "Calculate' and your answer should be 9.95 W/m^2.