Does anyone have a clue what this is?

[noamlivne]

there is quite a few of them loitering over here

Just a small remark about the video, and just to make sure you know it, you can listen to NXDN48 with a narrower filter of 4KHz, instead of 9.5KHz in DSDPlus, for example. That way you can pick up even weaker signals of NXDN48.