Strong HF signal
From Signal Identification Wiki
Transmissions happen on every second half of the hour. Frequency changes probably related to MUF. Signal level in Twente WebSDR has been as high as S9+50.
Video Examples[edit]
https://www.youtube.com/watch?v=iGT4g2M7DUA https://www.youtube.com/watch?v=8FtynD9c6uA&app=desktop https://www.youtube.com/watch?v=UV2bMFRp0LE https://www.youtube.com/watch?v=GnvwLhu0HOA&t=5s