This provided a practical detection range of 100 miles, enough to cover the Hanoi urban area and the main MiG base at Phúc Yên. A major disadvantage of this arrangement, however, was that most MiG contacts were beyond the 70-mile range of the Big Eye's APS-45 Height Finder radar, so that they were unable to provide this data to USAF strike forces. Furthermore, technical shortcomings in the EC-121D's systems precluded either controlling a fighter intercept or identifying a specific flight under attack.