INTRODUCTION TO SONAR 



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 Figure 6-4. — Exploded view of one scanning sonar transducer stave. 



Electrically, the magnetostrictive scanning 

 sonar unit acts as two independent transducers 

 housed in a common container. One of the 

 independent units is the search section. The 

 other is the maintenance of close contact (MCC) 

 section, located above the search elements. 



The search section is made up of 48 vertical 

 staves. Each stave consists of nickel laminations 

 and a polarizing magnet. Electrically, the staves 

 are Independent of one another. 



As its name implies, the MCC section is 

 used to maintain contact on a close-in sub- 

 marine. The MCC elements transmit in a de- 

 layed sequence from the top down, causing a 



phase delay of the sound beam, which results 

 in the top of the beam bending down toward 

 the delayed portion of the beam. The effect 

 resembles refraction. Transmission is at a 

 downward angle of approximately 30°. 



Because the elements are so placed that 

 they can cover a 360° area, there is no need 

 to rotate the transducer in scanning sonar. 

 Such an arrangement provides video coverage 

 simiiltaneously on all bearings. Audio coverage 

 is afforded by training a cursor to the desired 

 bearing. Most present-day magnetostrictive 

 transducers are built along the same general 

 lines. Physical dimensions vary according to 

 the operating frequency and power output desired. 



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