gear was reliable and accurate. Under the most favorable water 

 conditions surface ship propeller sounds could be heard at 

 ranges beyond 26,000 7/ards and the auxiliary machinery of des- 

 troyers detected up to approximately 1,000 yards. In the ab- 

 sence of controlling thermo-gradients the JP equipment usually 

 gave somewhat greater range than the supersonic gear. The 

 directionality of the JP system enabled an experienced oper- 

 ator to determine within approximately 1° bearings from a 

 source, such as cavitation noise, having considerable energy 

 in the higher sonic frequency region. 



Pro- submarine Devices. 



During the first two years of its existence Division 6 

 was able to contribute little direct assistance to our own 

 submarines. The German U-boat menace required almost complete 

 attention. Following the turning point in the antisubmarine 

 war in the late spring and early summer of 1943, however, it 

 was possible for the Division to devote an increasingly larger 

 portion of its activities to an intensive pro-submarine program. 



For some tine members of the Division had had in- mind many 

 ideas concerning helpful pro-submarine devices. As the pace 

 of the Pacific war stepped up, it became more and more important 

 to pet some of these devices into development and production. 

 Accordingly Messrs. Shea and Glennan, as representatives of 

 Division 6, visited the Pacific Fleet Submarine Force and with 

 squadron and division commanders and staff officers reviewed 

 the entire proposed program. 



Already a close and profitable association had been es- 

 tablished with ComSubDiv 41 in San Diego by the University of 

 California's Division of War Research. Hence during 1943, 

 as the inadequacy of our submarines' technical equipment 

 became more and more apparent, the emphasis of UCDWR's sonar 

 development program underwent a corresponding change in order 

 best to serve the needs of the submarine force „ 



In the fall of 1943, in order to obtain first-hand in- 

 formation concerning the problems and needs of our submarine 

 forces, Dr. Harnwell, Director of UCDWR, visited Pearl Harbor 

 and conferred there with Com Sub3Pac, and early in 1944 other 

 members of the UCDWR staff visited the submarine command in 

 connection with the planning and design of various sonar de= 

 vices. By the summer of 1944 some of the equipment developed 

 by UCDWR was ready for service testing and laboratorv engineers 



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