653 HYDROGRAPHIC MANUAL PaGE 608 



653. Comparison of East Coast and Vincent Sono-Radio Buoys 



From a structural standpoint the all-metal Vincent sono-radio buoy has numerous 

 advantages. Because of its compactness and weight it can be easily handled on small 

 survey vessels. It can be readily disassembled and stowed in a small space. The 

 single-bolt clamping ring permits easy access to the interior of the drum. 



The wooden East Coast sono-radio buoy is inexpensive and easy to build and, 

 despite its comparatively large surface exposed to wind and current, it has a greater 

 righting moment than the all-metal type of buoy. This righting moment results from 

 a heavy counterweight and a considerable length of structure below the waterline. All 

 this tends to make the wooden buoy long and comparatively heavy with the result 

 that it can be handled only on the larger survey vessels. A lighter model of this buoy, 

 however, has been built and used successfully (see 2841). 



Although the electric circuits of the two types of sono-radio buoys differ, they are 

 about equal from the standpoint of distance performance and reliability. A sono-radio 

 buoy is often wanted at the same station for several months in the waters off the West 

 Coast of the United States and off Alaska, and for this reason the Vincent sono-radio 

 buoy is designed for a long period of operation without service. A sono-radio buoy 

 used on the East Coast or Gulf Coast of the United States is normally not needed at the 

 same station for very long and is therefore designed for continuous service of not much 

 longer than 1 month. The cost of the electric equipment used in the two types is about 

 the same, but the cost of the wooden buoy structure is somewhat less than that of the 

 all-metal type. 



654. Adjustment of a Sono-Radio Buoy 



Before a sono-radio buoy is put on station the gain of its audio amplifier must be 

 set at the correct value to give opthnum operation. The proper gain of the amplifier 

 is determined as follows: 



(1) Put the sono-radio buoy on station with its gain control set at some arbitrary value. If the 

 value is too low, the buoy will be insensitive and returns will not be received from bombs at the ex- 

 pected distances; if the value is too high, excessive stray radio signals will be emitted by the sono- 

 radio buoy. Remove the sono-radio buoy and readjust the gain to a value assumed more nearly 

 correct and try it on station again. Continue this trial-and-error method until optimum gain value has 

 been found. Because of the differences in characteristics of sono-radio buoys — even those of the same 

 design — it is necessary to determine the proper audio-amplifier gain for each sono-radio buoy. With 

 experience, it is usually possible to adjust a buoy very close to optimum value at the first or second 

 attempt. It is usually necessary to do this only once for each sono-radio Ijuoy. 



(2) After the optimum gain setting has been found by (1), the sono-radio buoy should be brought 

 on board ship, and a direct or comparative measurement of the audio amplifier should be made, so 

 that the value of gain to be used for this particular sono-radio buoy is known for future use. Methods 

 for making such measurements are described in 6541 to 6544. 



(3) Each time before the sono-radio buoy is put on station the gain should be set at optimum 

 value by means of one of the methods described in 6541 to 6544. 



6541. Gain Measurements 



The method recommended for determining the audio-amplifier gain is by direct 

 measurement. This is necessary to be able to carry out (3) of 654. This method in- 

 volves the introduction of a known voltage into the input of the amplifier, and the 

 measurement of the resultant voltage across the output terminals of the amplifier. The 

 voltage gain of the amplifier is the ratio of the output to input voltages. This may also 

 be expressed in decibels, taking into account the input and output impedances. 



