570 THE BELL SYSTEM TECHNICAL JOtJRNAL, JULY 1951 



Fig. 8 — A composite pattern of horn and lens which shows that the lens delays the wave 

 fronts by approximately one wavelength. / = 9 KC. 



Fig. 9 — Flat phase fronts are obtained with a 30" diameter slant plate lens "illuminated" 

 by the y aperture feed horn of Fig. 8 placed at the focus. / = 9 KC. 



