Chapter 6— PRINCIPLES OF SONAR 



is a part of a separate unit— an azimuth indi- 

 cator (fig. 6-11). 



The paper recorder (on the upper portion 

 of the console) plots the bearing of all noise. 

 Operating in synchronization with the paper 

 recorder is the CRT. It indicates the location 

 of all noise-producing targets by inward deflec- 

 tions of the circular sweep. An audio channel, 

 provided with each azimuth indicator, permits 

 listening (with the aid of an external speaker) 

 to tiiis continuously scanning beam„ 



More detailed information on passive sonar 

 systems is contained in Sonar Teclinician ^ 

 3&2 . NavPers 10132. Also consult the manu- 

 facturer's technical m:inual supplied with each 

 equipment. 



FATHOMETER 



Water depths can be measured in several 

 ways. One method is to drop a weighted, distance- 

 m,irked line (lead line) to the bottom and observe 



the depth directly from the line. Chief dis- 

 advantages of this metiiod are that its use is 

 limrted to very shallow water, and the operation 

 is slow. 



The use of sound is the more common method 

 of measuring water depth. A sound pulse, directed 

 toward tlie bottom, is transmitted, and its echo 

 is received. The time between pulse transmission 

 and echo reception is measiu-ed and, based 

 on the speed of sound in water, the depth is 

 thereby determined. Such an echo sounding device 

 is known as a sonar sounding set, called a 

 fathometer. Basically the fathometer is a navi- 

 gational instrument, but because it operates on 

 the sonar principle, it usually is given to the 

 Sonar Teclinlcian for upkeep. 



One type of fathometer used aboard sliips 

 and submarines is the AN/UQN-1 sonar sounding 

 set, shown in figure 6-12. Several models of 

 the set are in use. Incur discussion the AN/UQN- 

 IC is representative of all the equipment modifi- 

 cations. 



62.10 

 Figure 6-13. — Depth recording showing a steady decrease in depth. 



101 



