Low Cost SDR Receiver for Medium Frequency R-Mode

Medium frequency R-Mode is a candidate to providing backup for positioning navigation, and timing, in case of an outage of the Global Navigation Satellite Systems. Its implementation and first results have shown good performance in the R-Mode Baltic Sea test bed. However, to make the technology available to a broad user group, the availability of a cost-efficient receiver is crucial. In this work, we compare four different implementations of SDR-based receivers for medium frequency R-Mode. More specifically, the performances of a LimeSDR, a RTL-SDR and the higher priced Ettus ecosystem will be presented. In addition, an oscilloscope is as SDR. Furthermore, the paper presents a GNUradio-based R-Mode receiver implementation, which is able to perform real-time positioning on the beat signal of the R-Mode signal for static cases with Hardware in the loop testing.