Characterization of a transmitter in a medium frequency maritime terrestrial navigation system

Due to the worldwide recognition of increased jamming and spoofing events, which threaten the usability of global navigation satellite systems (GNSS), positioning systems using signals of opportunity are gaining importance as backup systems. Especially for maritime usage, a terrestrial system called Ranging-Mode (R-Mode) is under development. Among other signals, it utilizes the maritime medium frequency broadcasts of the differential GNSS (DGNSS) service. Currently, the estimation of phase in a time continuous medium frequency signal is used to determine the distance between transmitter and receiver. Here, the delay of a transmitter on the signal phase is of great interest, since it directly affects the performance of the R-Mode system. In this paper, the influence of a medium frequency power amplifier is characterized as part of the transmitter chain. The aim is to give the operators of DGNSS stations the possibility to characterize their station themselves when the R-Mode system is operational. Therefore, widely used measuring instruments are utilized, rather than using well-known cost-intensive techniques like phase delay measurements. A simple setup with different evaluation methods that fit this requirement is presented. Furthermore, it is capable of measuring the absolute time delay. The presented workflow was tested on an amplifier with output power of 100 W at the transmitter station near Koblenz, Germany.