Fisher metal detectors In the late 1920, Dr. Gerhard Fisher, a German immigrant who studied electronics at the University of Dresden, obtained the first patent ever issued on aircraft radio direction finders. He was working as a Research Engineer in Los Angeles, California at the time and his work attracted the interest of Dr. Albert Einstein. After a demonstration of Dr.Fisher equipment, Einstein enthusiastically and correctly predicted the world-wide use of radio direction finders in the air, on land and at sea.