CHAPTER IX 



SONAR GEAR 



The wartime need of getting as much equipment as possible 

 into service in the least possible time meant that the scien- 

 tists and technicians of Division 6 had to turn reluctantly 

 but with determination from the work of fundamental research 

 and of developing new equipment, which they would have liked 

 to have done, to a program of improving equipment already at 

 hand - a program which they ruefully termed "gadgeteering, " 



As we have seen, many of the anti-submarine vessels of 

 the United States Navy were equipped with good serviceable 

 echo-ranging gear developed by the Naval Research Laboratory 

 and manufactured by the Submarine Signal Company and RCA 

 Manufacturing Company, Inc „ The program laid out for NDRC 

 was to devise auxiliary equipment and modifications which 

 could be applied in the shortest possible time to the echo- 

 ranging gear already installed,, 



Bearing Deviatio:. Indicator 



One of the most important improvements to the existing 

 searchlight beam type echo-ranging gear (described in Chapter 

 II) was the Bearing Deviation Indicator As finally developed, 

 BDI gave to the sonar operator a device which would indicate 

 on the cathode ray tube screen for each echo received whether 

 the target was to the right or to the left of the bearing of 

 the projector BDI was extremely valuable in helping the 

 operator keep track of a target during the initial rapid turn 

 when the attacking vessel sped toward the contact,, 



The developmental work on EDI was performed by the Harvard 

 Underwater Sound Laboratory BDI operated on the principle of 

 lobe comparison,, reinvented for this purpose by Dr Co K» 

 Stedman, Other early experiments were conducted by F. Vo Hunt, 

 J Lo Hathaway and X» No Butz, Jr 



HUSL was not only the developer, but for a time was the 

 producer of BDI equipment for the Navy n In all, HUSL con- 

 structed TO BDI auxiliary units Later commercially manufac- 

 tured equipment became available and eventually most of the 

 first-line antisubmarine vessels of the Navy were equipped 

 with BDI C 



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