RADAR ANTENNAS 



295 



much the same manner as in the SJ and SJ-1 antennas previously described. 



The antenna is illustrated in Fig. 47, With the SH system, the unit 



is mast mounted; for the Mark 16, the unit is mounted atop a 50 foot steel 



Fig. 46 — The SJ-1 /Mark 27 Submarine Radar Antenna. 



tower which can be erected in a few hours with a minimum of personnel. 

 The electrical characteristics are as follows: 



Gain— 21. db 



Reflector Dimensions 30" W x 20" H 



Horizontal beam width — 7.5° 



Vertical beam width — 12° 



Lobe separation — 5° approximately 



Loss in gain at lobe crossover — 1 db approximately 



Scan — (1) 360°, at 180 rpm for PPI operation 



(2) 360°, at approximately 1 rpm for accurate azimuth readings, with lobe 

 switching 



