Recently some interesting signals have been independently observed by several people, see, e.g., tweet. These are frequency hopping signals.
Tuning a KiwiSDR to 7812 kHz two of the signal fit into its passband. Below are TDoA maps for these signals. Note that these maps are likely biased by the fact that some of the KiwiSDRs might receive the ground-wave signal and others a sky-wave signal.
|TDoA cross correlations|
|TDoA cross corrlelations|