Cable Systems 



Figure 14 illustrates a cable system using all- 

 buoyant cable with the shock-cord suspension system. 

 The procedure used in this system was to let the suspension 

 and part of the buoyant cable drift out from the ship a pre- 

 determined distance, and hold the remainder of the cable 

 on the deck coiled in a figure-8. The figure-8 was used so 

 that there would be no twist in the cable as it was let out. 

 At the start of a run the cable would be payed out fast 

 enough to keep it slack but not so fast that it would tend to 

 coil up as it floated on the surface. This system stabilized 

 very quickly and there was little or no overloading of the 

 signal from the hydrophone when the cable was slack. The 

 recording time was limited to about 10 minutes with this 

 system, since at a typical ship-drift rate of 1 knot a 1000- 

 foot length of cable would drift out in about 12 minutes. 



A system using all nonbuoyant cable with the float 

 and line suspension is illustrated in figure 15. The float 

 provides enough buoyancy that the hydrophone would not be 

 pulled under by the weight of the nonbuoyant cable. In this 

 method of operation the floats and hydrophone would be 

 placed overboard with a nylon line attached to the floats. 

 About 300 feet of nylon line would be payed out, and also 

 all the cable, so that initially the system would be as shown 

 in figure 15. When ready for the test more nylon line would 

 be payed out and the system would slowly drift apart until 

 all slack in the cable would be taken up and the hydrophone 

 would start being towed. To repeat a run the nylon line 

 would be pulled in to about 300 feet as before. This system 

 took more time to stabilize than did the previous cable 

 system. "Blocking" of the hydrophone -preamplifier 

 occurred for some time after the release of the nylon line 

 at the start of the run because of excessively high voltage 

 levels probably caused by accelerations of the hydrophone; 

 however the system settled down and thereafter was quiet. 

 It was also noted that the combined weight of the cable and 

 the drag made it necessary to use quite a large force to 

 pull the cable back on board. It was feared that the cable * 

 might not stand up to repeated use in this way. 



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