INTRODUCTION TO SONAR 



A switch on the upper section of the instrument 

 allows rapid rewind and fast forward operation. 

 Instructions and procedures for using the switch, 

 as well as those for erasing and splicing the 

 tape, are also included in the instruction book. 



sonar can use either its hull-mounted or its 

 towed transducer, or it can transmit on one and 

 receive on the other. Either transducer may 

 transmit an RDT beam. Received signals are 

 presented in the normal manner at the master 

 consoles. 



VARIABLE DEPTH SONAR 



Thermal layers, as you know, reflect or 

 refract the sonar beam, making it difficult to 

 detect and maintain contact on a submarine 

 operating below the layer. To overcome this 

 detection problem, the variable depth sonar 

 (VDS) was developed. 



Modifications were made to existing sonars 

 to permit them to transmit and receive signals 

 through a transducer contained in a towed vehicle. 

 Two current VDS systems are the AN/SQA-10, 

 used in conjunction with the AN/SQS-29 and -30 

 sonar sets, and the AN/SQA-11, used with the 

 AN/SQS-23 sonar set. 



Modifications included the addition of a VDS 

 transmit scanner, receiver scanner, a-f ampli- 

 fier, and a relay-junction box. The shipboard 



Figure 6-18 shows the VDS transducer ready 

 for lowering. The transducer may be towed at 

 almost any speed and at depths to several hundred 

 feet. To stow the towed vehicle, the boom is 

 rotated so it faces forward and the transducer 

 is lowered onto a deck cradle where it is 

 securely fastened down. 



SONOBUOYS 



The sonobuoy is an expendable device dropped 

 from an aircraft into the sea. It detects under- 

 water sounds or echoes (depending on the type 

 of unit) and transmits the detected information 

 to the aircraft by means of a self-contained 

 radio transmitter. Some surface ships are also 

 equipped to receive the transmitted information. 



51.63 

 Figure 6-18. — VDS towed vehicle ready for lowering. 



108 



