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.