Early Skywave Detection Network: Preliminary Design and Analysis

A skywave signal is one has propagated by reflecting off the ionosphere. These signals are common in low frequency (LF) broadcast. However, in Loran, these signals are nuisances since they interfere with the more stable groundwave signal. Loran-C was designed with mitigations for the most common forms of skywave interference. However, these mitigations are not adequate to mitigate early skywave, a short delay skywave that interferes with the tracking point of the Loran signal. The interference can affect both the measured envelope and phase (timing) of the Loran signal. These effects can be deleterious for the accuracy and integrity of a Loran position solution. Preserving integrity is critical for safety of life application such as aviation landing. As such mitigations for early skywave need to be designed.