Very low frequency (VLF) time and frequency transfer signal analysis using KiwiSDR recordings

At a time when Global Navigation Satellite System (GNSS) signal spoofing and jamming has never been easier, time and frequency has become an ubiquitous commodity most distributed communication infrastructures rely on. Returning to the pre-space era of long range communication using very low frequency (VLF) signals, we investigate some of the remaining VLF time and frequency transfer signals. Despite their long communication range, the need for bulky antennas and low VLF noise environment makes the direct reception of these signals impractical. In this presentation, we collect timestamped records of VLF signals collected throughout the world from the KiwiSDR network, and assess the performance of the broadcast signals and the receivers.