Appl. Sci. 2023, 13, 1872 
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Groß Mohrdorf station. In detail, a phase jump in the order of 40 m is visible for Groß 
Mohrdorf, lasting approximately 25 min. It is interesting to observe that the jump affects 
one of the signals, the CW2, but not the other. This behaviour was observed from time to 
time, with varying severity—a clear cause has not yet been identified. In the future, these 
instabilities can be avoided by identifying their source or by using monitor stations with 
correction information sent to the R-Mode users by specific R-Mode messages. 
30 
CW1 
CW2 
10 
MT 
V 
Mr 
A 
— 30: 
E 
nn 
5 20 
- phhse jump — 
LQ 
) 
22:30 22:35 22:40 22:45 22:50 22:55 23:00 23:05 23:10 
UTC Time 
A 
23:15 
Figure 5. Instabilities of Groß Mohrdorf radio beacon. The phase error in meter is represented for the 
wo CW signals. 
Part of the analysis and characterization of the transmitter chain has already started, as 
presented in [27]. In future projects, a deeper and more accurate analysis of the transmitter 
chain will be carried out in order to identify the source of such instabilities and implement 
a solution. Alternatively, on the receiver side, a detection mechanism in combination with 
a correction or exclusion technique can be applied to solve this issue. 
4. Mf R-Mode System Accuracy: Results and Discussion 
In this section, the performance of the system will be demonstrated mainly in terms of 
the horizontal positioning accuracy for the daytime scenario, with a negligible impact of 
:he AGDF, and for the nighttime one with the presence of sky-waves. In February 2021, the 
DLR, with the support of the partners involved in the R-Mode Baltic project, performed 
a measurement campaign in the southern Baltic Sea on board the vessel Deneb that was 
provided by the BSH. The test area is located near Rostock and is visible in Figure 6 as a red 
rectangle. During the measurement campaign, only six out of the eight available R-Mode 
transmitters were operational, namely Groß Mohrdorf, Rozewie, Hammerodde, Helgoland, 
Holmsjö and Hoburg. They are visible as yellow triangles in Figure 6. 
An interesting piece of information to keep in mind is the distance between the 
different MF radio beacons and the centre of the test area. This is given in Table 1. As is 
clear, some of the stations were located at a distance greater than the assumed approximated 
coverage of 250 km, such as Hoburg, Rozewie and Holmsjö. Despite the significant distance, 
they were received with good accuracy during the day, as will be demonstrated in the next 
section, while they were excluded from the positioning solution at night due to the strong 
influence of the sky-waves.