A U.S. Navy technican uses a portable test set to test the doppler radar navigational system of a Sikorsky SH-3A <i>Sea King</i> before flight at Naval Outlying Landing Field Imperial Beach, California (USA), circa 1967.
USN
<a rel="nofollow" class="external text" href="http://www.navy.mil/ah_online/department_arch.html">U.S. Navy All Hands magazine</a> <a rel="nofollow" class="external text" href="http://www.navy.mil/ah_online/archpdf/ah196707.pdf">July 1967</a>, p. 62.