peak output. Signals produced can be checked 

 either by the survey vessel radio or by a volt- 

 ohm-milliammeter. ' All this work can be ac- 

 complished by the shore station or the survey 

 vessel, depending upon facilities. If the initial 

 work can be carried out ashore, and the final 

 check made on the vessel before the buoy is 

 planted, much valuable time can be saved. 

 The buoy complete with meters is now ready 

 for the plant. 



9-58 Planting the Roberts Buoy.— At the 

 current meter station the buoy is lowered into 

 the water from the survey vessel. Caution 

 should be exercised when carrying out the plant 

 to prevent entangling the meters and support- 

 ing cables. The three types of plants most 

 commonly used, depending on the placement 

 of the ship's gear, are as follows: 



1. Bow Plant — Boom and winch forward. 

 The vessel approaches the station with the 

 current, lowers the meters and then the buoy 

 over the bow. It then backs down slowly and 

 drops the buoy anchor. 



2. Fantml Plant — Boom and winch aft. The 

 meter station is approached with the vessel 

 heading into the current. Lower the meters and 

 then the buoy from the quarter; then proceed 

 ahead slowly and drop the buoy anchor. 



3. Stationary Plant—Bovf or fantail. The 

 vessel lays to at the meter station. Plant the 

 buoy from the weather side of the vessel. Allow 

 the ship to drift away from the buoy and drop 

 the buoy anchor. 



9-59 Inspection and Servicing During Op- 

 eration. — Once the buoy is planted and in opera- 

 tion, it should operate independently for the 

 duration of the station. Each meter station 

 should operate normally for approximately 15 

 days on 1 supply of batteries. Inspection and 

 servicing of the station is made every 100 hours. 

 Should the meters show evidence of marine 

 fouling, they must be cleaned. In areas of silty 

 water, the impeller lignum-vitae bearings must 

 be inspected for evidence of scoring and replaced 

 if necessary. 



9-60 Operation of the Instrument and Re- 

 cording the Data. — After the buoy plant, fur- 

 ther observations will be taken from the ship 

 or shore monitor station. Fifteen meters, rep- 

 resenting 5 operating buoys, can be monitored at 

 a single receiver, although the normal load is 

 usually 9 meters operating from 3 buoys, with 

 1 meter held in reserve. A crystal-controlled 

 oscillator duplicating the crystals at each meter 

 station is provided at the receiver. This serves 

 to pinpoint the operating frequency for maxi- 

 mum accuracy. Once the receiver has been 

 tuned to the required frequency, the observer 



H. O. 607 



is ready to record the data in the Record of 

 Current Observations for Roberts Radio Cur- 

 rent Meter, PRNC-NHO-1505. Recording time 

 is usually 1 minute per meter for each station, 

 with observations bemg taken at half-hour inter- 

 vals. The signals produced by the meters are 

 transmitted to the receiver which converts the 

 audio signals to electrical impulses, routes them 

 through a relay box, and records them on a tape 

 chronograph. The break-circuit chronometer 

 introduces a time signal, enabling the velocity to 

 be interpreted correctly. A diagrammatic sketch 

 of the receiving station is shown at top of figure 

 9-7. If the signals produced are too far below 



CHRONOMETER 



TEST OSCILLATOR 



CHRONOGRAPH 



A SHORE 



CHRONOMETER 



: 



CHRONOGRAPH 



B SHIP 



Figure 9-7. Diagramn\atic sketch of the receiving 

 station, 

 (a) Using station. (6) Using di- 

 rect contact. 



the noise level to be recorded automatically, 

 but are distinguishable audibly by loudspeaker 

 or earphone, automatic recording is then 

 switched off by the controls provided. The 

 chronometer continues operation, and the ob- 

 server produces hand-controlled signals by key 



99 



