6713 HYDROGRAPHIC MANUAL PaGE 628 



bomber, but the interval of time between positions, known as the bombing interval, is 

 decided by the officer-in-charge. 



6713. Radio Technician 



The radio technician assigned to each watch is in charge of the instrumental 

 equipment, under the supervision of the chief radio technician. He should see that all 

 the required switches are turned on, that the radio receiver is properly tuned to receive 

 the radio signals and aid, if possible, in the identification of the returns from the various 

 H.A.R. stations. During excessive static he should be especially vigilant to see that 

 the gain of the amplifier is properly adjusted to receive radio returns with a minimum 

 of spurious marks on the chronograph tape. There should be a sufficient number of 

 radio technicians so that there is one for each watch, in addition to the chief radio 

 technician who should be free to maintain and repair R.A.K. equipment. 



The radio equipment used in R.A.R. is highly specialized and, as the success of 

 the method depends, to a large extent, on its satisfactory operation, it is essential that 

 the radio personnel be of the liighest type and thoroughly trained. They should have 

 a basic knowledge of radio communication, but the specialized training can be obtained 

 only by actual operation of the R.A.R. equipment under competent supervision. 

 Graduates from good radio schools, or technicians who have been connected with com- 

 mercial broadcasting or experimental investigation, are usually most satisfactory in 

 R.A.R. 



6714. Bomber 



One member of the crew is assigned as bomber for each watch, supervised by a 

 chief bomber, who stands one of the watches and also has general charge of the pre- 

 liminary preparation of the bombs, the care of the explosives, and their stowage. At 

 receipt of the signal designating the size of bomb (see 6741), the bomber selects the 

 bomb, completes the final preparation (6842), and stands near the lighting unit ready 

 to light the bomb at the signal. When the signal is received, he lights the bomb and 

 throws it overboard, and as it strikes the water he gives the "bomb over" signal by 

 means of a portable electric push button, which he carries in his hand. This signal is 

 the official time of the position. It is received simultaneously on the bridge and at the 

 ehronograph station. The recorder on the bridge has the log read, and any other 

 supplemental data are observed that are desired at the time of the position. 



The assignment of members of the crew as bombers is very important. The ones 

 selected preferably should have had considerable experience with explosives and should 

 have a sound knowledge and an intelligent understanding of their use — the kind of 

 knowledge that may be best gained by experience. An inexperienced man should always 

 be given definite instructions before he is allowed to handle explosives and then should 

 work under the supervision of a careful experienced man until he demonstrates that 

 he can be relied on not to endanger himself or his shipmates. Men who, through 

 ignorance, carelessness, or bravado, follow unsafe practices must not be allowed to 

 handle explosives. 



672. Ship Equipment for Radio Acoustic Ranging 



The special electric equipment on the survey ship used for R.A.R. includes the 

 hydrophone, radio receiver, chronograph amplifier, chronograph, break-circuit chronom- 

 eter or criftig '(6734), and communication system. Their coordinate functions from 



