the choice of frequency for radio navigation is a subject of considerable depth and is inextricably intertwined with requirements for range, accuracy, reliability, cost and impact on competitive services using radiowaves. The basic information for passing judgment on these items comprises the limitations imposed by nature on the system. These limitations are the laws of physics governing the propagation of radio waves.
We note in particular that great ranges and hence large coverage areas can be obtained at opposite ends of the spectrum in the OMEGA and SATELLITE systems. We find that great accuracy is accomplished with the ground wave propagation mechanism in the form of Loran–C and Loran–D. We observe that the choice of modulation is critical if high accuracy of position is an objective or requirement.