n radio telecommunications, effective radiated power or equivalent radiated power (ERP) is a standardized theoretical measurement of radio frequency (RF) energy using the non-SI unit dBd, and is determined by subtracting system losses and adding system gains. ERP takes into consideration transmitter power output (TPO), transmission line losses, connector losses, antenna directivity, and height above average terrain (HAAT). ERP is typically applied to antenna systems. For a simplified example, if an antenna system has 9 dB gain and 6 dB loss, its ERP is 3 dB over the TPO.