This is a lightweight beacon transmitter designed to be carried aloft by balloons. Several prototypes have been launched and one is now on its third circumnavigation of the planet.
One of the things that make this transmitter unique is that, in addition to WSPR transmissions on 20m, a glyph (yeah, I had to look it up) is drawn when the received audio is sent to ARGO. An avatar written by RF - Rudolf Hell would be proud!
You can monitor the progress of U4B-6 here and, if using ARGO, you may see a depiction like the one below.