Since the Navy desired all-weather capability and the ability to carry and launch radar-homing missiles such as the AIM-7 Sparrow, the small radar of the YF-17 had to be replaced with more powerful gear that could effectively handle beyond visual range (BVR) missiles. The Hughes APG-65 digital multi-mode radar with pulse-Doppler beam sharpening was selected over its Westinghouse competitor. This required an enlarged nose to accommodate the four-cubic-foot, 340-lb system (not counting the 28-inch radar dish) in order to meet the Navy's search range requirement of over 30 nm.
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The water-cooled APG-65 has 8,000 less parts than the F-4 Phantom's radar, yet 20 percent greater range. It operates in the I/J-band (8-12.5 GHz). The set is provided with built-in test equipment (BITE), which assists in identifying and isolating failures. According to Hughes, this "provides total end-to-end radar preflight checkout and continuous monitoring". Some two dozen onboard computers operate in conjunction with the radar and weapons delivery systems.
