The AN/APQ-13 was an X-band, ground scanning radar developed by Bell Laboratories, Western Electric, and MIT as an improved model of the airborne H2X radar, which was in turn developed from the first ground scanning radar, the British H2S radar. The AN/APQ-13 radar operated at a frequency of 9375 ± 45 megahertz and used a superheterodyne receiver. Carried on the aircraft belly between the bomb bays, the AN/APQ-13 was used on B-29 bombers during World War II in the Pacific theater for high altitude area bombing, search and navigation. Computation for bombing could be performed by an impact predictor. A range unit permitted a high degree of accuracy in locating beacons.
After the war, the AN/APQ-13 radar was was converted to civilian use as a weather warning radar. About 30 systems were converted, starting in late 1945. They were installed at military bases. The last operational APQ-13 was removed from the Fort Sill, Oklahoma post weather station in October 1977 for display at what is now the National Museum of the United States Air Force. The museum intended to display it in its original configuration as a navigation and bombing radar, but would note the radar's much longer history as an operational weather radar. The AN/APQ-13 radars were generally replaced by the AN/CPS-9, which was specifically designed as a weather radar.