Page 495 echo sounding 527 



time-delay relay. The high-voltage 0.02 microfarad no ise-suppressing condensers across the rectifier tubes may short-circuit, causing 

 the line fuses to blow out, or they may open-circuit, in which case strays will be registered on the indicator dials at normal gain of the 

 17.5-kc echo amplifier (51). Strays will also be caused by faulty type 807 tubes (56), particularly when the screen voltage on these tubes 

 is much over 200 volts. Also if the 17.5-kc oscillator (55) is too near the point of oscillation due to improper adjustment of the keying 

 circuit (par. (c) ), spurious signals may be transmitted. Such spurious signals and the resultant echoes, when registered on the indica- 

 tor dials, may appear as strays because of the irregularity of transmission. 



(n) Sonic transmission and reception. — If the 525-cyele motor generator (58) fails to start when the starting-relay circuit is com- 

 pleted by the starting-frequency switch (41i) on position 5, measure the voltage across the switch points involved and the UO-volt d-c 

 ship supply line. Test the d-c line fuses and the starting relay. 



If the motor generator (58) is operating and the keying relay is functioning properly but no signal is transmitted, test the fuses 

 protecting the specific type 324 oscillator (63) which is connected. There are normally two of these oscillators, each separately tuned 

 electrically, and when sounding in deep water they may be used interchangeably. However, in shoal water, if they are located at 

 different distances from the hydrophone (64) used, the separation factor (see 556) will be different for each. And if the draft of each 

 oscillator is not the same thty cannot be considered interchangeable for shoal-water sounding. 



The selection of these oscillators (63) is made by means of switches on the 525-cycle power-supply panel. Each oscillator is sepa- 

 rately tuned by series condensers. The value of the series capacitance in either case should be adjusted to give the maximum trans- 

 mitted signal intensity at the optimum frequency. This value of capacitance may be assumed to be that which results in a maximum 

 current flowing into the oscillator at the optimum value of frequency. 



The strength of the echo signal may be increased by adjusting the frequency of the electric current through the oscillator (63) t» 

 the optimum value. This adjustment is made by regulating the speed (59) of the motor generator by means of a rheostat in the field 

 circuit of the generato'V, or by adjusting the governor on the motor generator if it is so equipped. 



If the keying relay (60) is not functioning properly, make the necessary adjustments as described in (d). 



(o) Polari2tng circuit for the transceiver. — Note the reading of the meter measuring the d-c polarizing current supplied to the trans- 

 ceiver (61). If the value is not approximately 1.7 amperes, test the various elements in the polarizing-current rectifier circuit (62). 

 Test the insulation of the transceiver (61) and connecting line after disconnecting the latter from the filter-junction box. 



Faulty operation of the copper-oxide rectifier, or faults in the other circuit elements and the connections (62) may cause strays 

 to be registered on the dials of the indicator. 



(p) Alternate hydrophones and oscillators.— \i the hydrophone (64) is possibly at fault, try the alternate one provided. If the 324 

 oscillator (63) is suspected, try the alternate oscillator. The tuning of these oscillators is discussed in (n). 



(?) Electric machinery noise. — A turbogenerator or a rotary converter (65) is used to furnish the 110-volt 60-cycle power necessary 

 to operate the Dorsey Fathometer No. 3, and must be started before the instrument can be operated. If the collector rings on the 

 generator (65) become irregular due to wear, sparking at the brushes will result. Sparking will also be caused by excessive vibra: 

 tion of the brushes bearing against the rings. Such sparking, if aggravated, will cause strays to be registered on the dials of the indi- 

 cator. The collector rings should be kept clean and should be turned down when necessary. And the brushes should fit properly in 

 the brush holders. 



If a noisy llO-volt d-c ship supply (66) is used as a source of power to operate the sonic amplifier (53), strays may be registered. 

 Similarly if the sonic amplifier (53) is operated from a noisy source of llO-volt 60-cycle- power (67), such as an inverter or a generator 

 with rings and brushes in poor condition, strays may be registered. 



(r) Acoustic and electric noises. — As indicated in ((?), noise causing the registration of strays on the dials of the indicator may be 

 of an electric nature. Such noises may originate in any of the various parts of the instrument. The isolation of the source of electric 

 noises is accomplished simply by disconnecting or turning off the various parts. If the source is found to be located in the circuits 

 (18, 19, 20) which cause the index neon tubes (15, 16, 17) to flash, refer to (0 and (g). If the electric noises originate in one of the echo 

 amplifiers (51 or 53), this fact may be determined by grounding the input terminals, assuming the fault is not in the circuits causing 

 the neon tubes to flash. If the strays persist, the trouble is in the amplifier and may be due to oscillation or to faulty tubes, parts, 

 or insulation, particularly of the input and output circuits. If the strays are caused by voltage picked up by the supersonic amplifier 

 (51) from the 1025-cycle power supply (50), this will be indicated by a stationary pattern of registration on the 20-fathom.dial when 

 the driving motor (47) is ruiming at synchronous speed, and may be proved by removing one of the type 6C5 tubes from the tuning- 

 fork circuit (49). 



If the noise is found to originate in the hydrophone (64) or the transceiver (61) circuit, and is found not to be caused by disturb- 

 ances of an electric nature, the source must be of aii acoustic nature and will be found within the vessel itself, or in the water. If 

 the noise is not due to the propulsion and passage of the vessel through the water, it may be caused by the main engines, the auxil- 

 iaries and appurtenances such as pumps, or by members of the crew chipping paint or making repairs. 



527. Veslekari 



The Veslekari echo-sounding instrument is a graphic-recording type designed for 

 hydrographic surveying m moderate to deep depths. This instrmnent is made by 

 Henry Hughes & Son, Limited, of London, England. The useful sounding range is 

 from 7 to 1,000 fathoms. Two Veslekari instruments are in use on Coast and Geodetic 

 Survey ships in 1942. 



The entire system is composed of five separate units. They consist of the record- 

 ing mechanism and echo amplifier together in one cast-metal housing, battery com- 

 partment and charging panel, contactor box, the magnetostrictive transmitting unit, 

 and a similar receiving unit. The front of the compartment containing the recording 

 mechanism is hinged to give access to its contents, and the echo-amplifier equipment 

 is mounted on the inside of a removable panel to make it accessible. 



