One-Way Frequency Transfer Using Medium-Frequency R-Mode for GNSS-Denied Environments

Kurzfassung

Synchronization of many distributed technical sys- tems and applications is heavily dependent on GNSS. Jamming of the GNSS spectrum is already a common problem, and coherent spoofing poses a realistic threat to critical infrastructure that relies on GNSS for its time and frequency reference. This study demonstrates the feasibility of one-way frequency transfer using medium-frequency (MF) R-Mode, a technique previously developed and deployed for positioning in the maritime domain but now adapted for high-stability timing. Field validation was performed during Jammertest 2025 in Norway, where a tempo- rary R-Mode station was established. We successfully measured the drift of a rubidium atomic clock (10 MHz output) using R-Mode phase data and validated the drift against a local reference during GNSS-denied operation. The paper shows that we were able to estimate the drift of the local rubidium clock with an uncertainty of 10−10, which matches the specification provided by the clock manufacturer. Index Terms—Medium-frequency R-Mode, one-way frequency transfer, GNSS denial, time-frequency dissemination, rubidium clock, maritime navigation, jamming resilience, phase-based synchronization.