5.  a, b, c.  The answer to all three is Houma AFS, LA (M-126 / Z-126), home to the 657th Radar Squadron.  The AN/FPS-28 prototype, designed and built by Raytheon, was considered too complex for further production.  The radar antenna was mounted atop a steel-truss tower, somewhat similar to the prototype AN/FPS-24 tower at Eufaula AFS, AL.  [An AN/FPS-67B search radar was also operated at Houma AFS in addition to the AN/FPS-28.]