Thus for radiated power of 1 kW, E_0 = 300 mV/m at a distance of 1 km and E_0 = 186.45 mV/m at a distance of 1 mile. For other values of radiated power, E_0 will be proportional to the square root of the power P and will accordingly be modified in accordance with the directivity in horizontal plane, and for any added directivity when the field is not proportional to the cosine of the angle of elevation.