drydocked for movement or adjustment of the transducer. The AN/UQN 

 Sonar Sounding Set is considered typical of the deep water instruments. 



Several different transducers have been used with the deep water 

 instruments. The standard 12-inch transducer supplied with the AN/UQN 

 uses a frequency of 12 kilocycles andhas a beam width of approximately 

 60° and a depth range to 6,000 fathoms. An experimental, stabilized 

 transducer, built by the David Taylor Model Basin, is 40 inches in 

 diameter and has a cone width of 16° with a 12-kilocycle signal, or 6° 

 with a 34-kilocycle signal. The second combination, however, provides 

 a usable depth range of only about 1,000 fathoms, although depths as 

 much as 2,000 fathoms have been recorded under exceptional conditions. 

 General Electric has developed a new unit, the AN/SQN-6, which is a 

 modification of the standard AN/UQN sonar set. This unit transmits 

 on a frequency of 18 kilocycles and uses a newly designed 25-inch, 

 stabilized transducer which gives a beam approximately 18° wide. 

 The AN/SQN-6 has recorded depths of about 3,000 fathoms without 

 difficulty. 



For precision surveys in deep water, it has been found advantageous 

 to use an expanded- scale recorder in place of the recorder supplied 

 ■with the set. Two such recorders are now in use: the Precision Depth 

 Recorder (PDR) and the Precision Graphic Recorder (PGR). 



a. Precision Depth Recorder (PDR) 



This recorder is built by the Times Facsimile Corporation 

 as a modification of the Times Facsimile radio receiver. The PDR 

 uses an electro- sensitive paper, has a paper speed of 24 inches per 

 hour, and displays 400 fathoms over a width of 18.85 inches. It phases 

 automatically so that depths to the full range capability of the sonar 

 set can be recorded in increments of 400 fathoms with high precision. 

 The PDR triggers the sonar set and performs the time measuring 

 function to about one part in a million. However, the equipment has 

 a 400-fathom phase ambiguity, because no positive indication is given 

 as to which multiple of 400 fathoms is being displayed on the record. 

 In addition, the fact that the sonar set was not designed to operate 

 with this recorder leads to overloading of the sonar set when sounding 

 work is carried on continuously over long periods of time. 



b. Precision Graphic Recorder (PGR) 



This instrument, built by the Alden Electronic and Impulse 

 Recording Co. for the Woods Hole Oceanographic Institution, is 

 similar to the PDR, but it is considered to be more versatile in that 



XI- 3 



