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as discussed in Section 11.2. Such an antenna is also required to obtain 

 the high angular precision for anti-aircraft fire control. These require- 

 ments are achieved by the use of a conical scanning system. The beam 

 from the antenna describes a narrow cone and the deviation of the axis 

 of the cone from the line of sight to the target can be determined and meas- 

 ured by the phase difference between the amplitude modulated received 

 signal and the frequency of the reference generator associated with the 



Fig. 54. — Rocking Horse Fire Control Antenna. 



antenna. This information is presented to the pointer-trainer at the direc- 

 tor in the form of a wandering dot on an oscilloscope. 



The antennas described in sections 14.10, 14.11 and 14.12 were all designed 

 by the Bell Laboratories as anti-aircraft fire control radar systems, particu- 

 larly for directing heavy machine guns. They were designed for use on all 

 types of Naval surface warships. 



In Radar Kquii)ment Mark 19, the first system to be associated with the 

 control of 1.1 inch and 40 mm anli-aircraft machine guns, the antenna was 

 designed for operation in the 10 cm region. This antenna consisted of a 

 spinning half dipole with a coaxial transmission line feed. The antenna 



