The purpose of the package is to answer the question 'What is the radio field strength at a certain point?' when power is radiated from a transmit­ ting source. Because of the complexity of the question in general, it can only be answered at present in certain idealized situations. Nevertheless it is valuable to have quantitative data available for these situations. The package is divided into two parts. In the first of these, propagation in free space and over a flat earth are dealt with. In the second, propagation over a spherical earth is considered. In the free-space situation the power density of the signal in a given direction will fall as the inverse square of the distance from the source. For propagation from a transmitting source at an arbitrary height above a perfecdy conducting flat earth, the field strength at large distances can be 3 dB higher than in free space. With a finite conduc­ tivity earth, the field strength will be lower than this because of the power dissipation in the earth.