Page 629 



KADIO ACOUSTIC RANGING 



6721 



the time a bomb explodes until the radio signals from the R.A.R. stations have been 

 recorded on the chronograph are as follows: 



The explosion of the bomb is received on the hydrophone and the signal is increased. 

 by an amplifier sufficiently to operate the stylus of a chronograph which makes a mark 

 on a moving tape. The stylus circuit is then immediately connected either manually or 

 automatically to the output of a radio receiver. Tlu-ough this the radio signals from 

 the distant R.A.R. stations are received and actuate the stylus, which marks each 

 signal on the tape. During this period, from the time the bomb was thrown overboard 

 until the reception of the last radio signal, regular time intervals are being marked on 

 the chronograph tape by another stylus operated from a break-circuit chronometer or 

 from the criftig. Thus the time intervals from the explosion of the bomb to the recep- 

 tion of the various radio signals may be measured on the tape. 



A buzzer or other signal system is used to signal between the several stations so as 

 to coordinate their respective functions. A communication system between the chrono- 

 graph station and the plotting room is also necessary. 



Where R.A.R. shore stations are used, the R.A.R. equipment of the survey ship 

 includes a medium-power short-wave transmitter to communicate with these stations. 



.....TV 



RADIO RECEIVER 



w = Ohms 

 M = 1000 o) 

 jx = lOOOOOOai 

 juf = Microfarads 



Figure 140.— Circuit diagram of R.A.R. equipment for survey vessel. 



6721. Hydrophone 



The hydrophone used on the vessel for the reception of the bomb signal may be 

 either the Submarine Signal Company watch-case type ISiE, the rubber rat (K-tube 

 unit), or the tuned hydrophone 341.4, all of which are described in 5213. Each of these 

 uses a carbon-button element. The hydrophone is installed in a water-filled tank which 

 is fastened to the inner side of the hull of the ship. A suitable tank is the Submarine 

 Signal Company 3565 which is used for the 312 Fathometer. This hydrophone, as for 

 echo sounding, should be located where undesired noises will be received at a minimum,. 

 as described in 541 (see also 5148). 



