How Do You Calculate Effective Radiated Power?
To calculate the effective radiated power of a radio station you need to know the power output of the transmitter, the power loss in the antenna feed line and the power gain of the antenna. When you have these three figures you can find the actual power being radiated by the antenna system. A large commercial FM station might have as many as twenty elements in the antenna system while a small station antenna system might have only one. The basic theory of effective radiated power would be the same. Find the listed power output of the transmitter in the operating manual. The final power output of the transmitter may vary slightly from the listed ,figure so a check of the actual output should be made with a watt meter which has been calibrated. Check the feed line loss. The loss of transmitter power through the line is determined by the length and size of the coaxial cable. A chart showing line loss from commonly used cables is available on line from the Iowa Repeaters Association. Check
