''An improved version of an early ship-borne radar.<br>Although it was designed for anti-air, it can also be used as a surface radar.<br>Though the smaller and easier to handle Type 13 RADAR was more widely used amongst small ships, the Type 21 RADAR was installed on the aviation cruiser "Mogami" and the Akizuki-class, with this model being a what-if upgrade of that RADAR.