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tical axis and a tilt joint on the horizontal axis. Either vertical or hori- 

 zontal polarization can be used by rotating the mounting position of the 

 emitter. Vertical polarization is preferred for aircraft interception work 

 and horizontal polarization is i)referred for sea search work. 



Fig. 61— SCR-520 Antenna. 



For aircraft interception the military services desired to scan rapidly a 

 large solid angle forward of the pursuing airplane, i.e. 90° right and left, 15° 

 below and 50° above the line of flight. The data is presented to the opera- 

 tor in the form of both "B" and ''C" })resentations and for this purpose 

 potentiometer data take-offs are provided on the antenna. The reflector 

 is spun on a vertical axis at a rate of 360 rpm and at the same time it is 



