I acquired a DTX1 DATV transmitter. Although this is rather dated now it is still a useful tx capable of transmitting between 350 and 1350MHz. As a test setup over my usual 6″ or so transmission path here it is on 437MHz transmitting a test card (yes the test card is all wrong but at least has the callsign and it is unlikely to propagate beyond the garden).
The test card is coming from a little device that reads an SD card (and other formats) and sends a selected image. I did try an old digital camera I have which has video output but which refused to do anything, not even when plugged into a TV. Anyway it proves the DTX1 works.