2612 



HYDROGKAPHIC MANUAL 



Page 148 



qiiirements for a shore station site, in the approximate order of their importance, are 

 as follows: 



(a) The shore station site must be within a reasonable distance of the hydrophone (see 2612) 

 and usually convenient thereto. If practicable the hydrophone site should be visible from it so that 

 the station operator can notify the ship personnel when small boats cause interference. 



(b) It must be accessible by water or overland transportation. 



(c) Fresh water should be available at the station and supplies should be obtainable in the 

 vicinity for the station personnel. 



(d) It is desirable to house the station and personnel in existing facilities on shore, otherwise a 

 house must be built or tents erected for this purpose. 



RUBBER COVERED CABLE 



SMALL BOAT 

 ANCHOR 



ANCHOR. 60 TO 100 POUNDS, 

 JN 15 TO 20 FATHOMS 



FiGUKE 42.— R.A.R. shore station (general arrangement). 



2612. Hydrophone 



The hydiophone unit used in the shore station equipment must be in a light con- 

 tainer of sufficient size and displacement to furnish buoyancy. It should be provided 

 with a valve and be strong and tight enough to contain air under pressure (see 6563, 

 Vincent Hydrophone). A large container, 24 inches in diameter, made of K-inch boiler 

 plate, has been used successfully with about 35 pounds of air pressure. 



The hydrophone is anchored in depths of 15 to 20 fathoms (see fig. 42) so that it 

 floats submerged 7 to 10 fathoms below the surface of the water. An anchor of scrap 

 iron, weighing from 60 to 100 pounds, is attached 5 to 13 fathoms from the end of the 

 cable to which the hydrophone is attached. This holds the unit at the desired depth 

 below the surface. One end of a length of %-inch wire rope, about as long as the water 

 is deep, is attached to the hydrophone anchor and stretched along the bottom, a small 

 boat anchor being attached to the other end. A small marker buoy is secured to the 

 boat anchor for use in recovering the hydrophone. The hydrophone and the buoy 

 must be separated far enough so that there is no likelihood of the hydrophone becoming 

 fouled. All connections and shacldes must be made tight so that the motion of the 

 water cannot possibly make them clank or rattle in the slightest, to cause unwanted 

 noises in the hydrophone. 



a. Hydrophone site. — The selection of the hydrophone site is the most important 

 factor in the establishment of a shore station. The hydrophone should be located at 

 the edge of a slope into deep offshore water. Shoals and submarine valleys between 

 the hydrophone and the area being surveyed are apt to mterfere seriously with the 

 transmission of sound. The hydrophone should be located as close as practicable to 

 the beach so that only a short length of cable is necessary. 



