Measurement and Analysis of Loran-C Sky Waves throughout the Day

Abstract

In this study, Loran-C signals were collected throughout the day, and the characteristics of the received signals at different propagation distances were analyzed. Because the signal amplitude is small and difficult to recognize at a long distance and there is mutual interference between stations, a linear average method is used to process the received signal. At locations closer to the receiver, clear observations of the time delay and amplitude variation in the one-hop sky wave can be made by using the ground wave as a reference, which can be applied to studying the characteristics and parameter inversion of the lower ionosphere. When the distance is further, the significant enhancement of the sky-wave signal during the night may lead to decreased accuracy in timing and positioning. When the distance is much larger than the propagation range of the ground wave, only the sky-wave signal can be received, and the signal is more stable than when the distance is closer. During the night, multiple amplitude-comparable multi-path signals may appear in the sky wave, making the identification of the one-hop sky wave more difficult.