Early Radio Navigation Systems

While ships sailed the seas since nearly prehistorical time, incredible feats were reached in the X-XVIII centuries with relatively simple instruments for astronomical navigation. Starting in XVIII century, the development of much more precise octants, sextants and, later, marine chronometers, allowed very precise astronomical navigation, yet bad weather remained a major impairment. The invention of radio, late in the XIX century, immediately gave birth to the idea of radio beacons, analogous to conventional lighthouses, but exploiting radio waves. The early systems had limited range and poor directivity but very ingenious solutions were developed to attain an acceptable precision. A selection of these will be presented in this contribution.