The first person to create a device to hook up a deflectable cathode ray tube with a phosphor screen to display shapes and images was either K. Ferdinand Braun in 1897 or Boris Rosing in 1907, depending on precise definitions and whether you're taking to Germans or Russians.
Earlier devices had included deflected cathode rays, and cathode rays and phosphor screens, since the 1850s, but these were the first unambiguously controllable image-making machines.
By the 1920s, commercially available oscilloscopes employed CRTs for display (earlier oscilloscopes had used pens or pencils at the end of rods that were deflected up and down on paper that rolled by at a constant rate).
The first device generally called a television was made in Germany in the early 1930s.
I can't speak to radars specifically, but the technology certainly existed.