monitored by a single shore station. The data 

 are interpreted, scaled, and plotted on graphs 

 at the station for processing at the Hydro- 

 graphic Office. 



9-54 Equipment Needed To Operate the 

 Roberts Radio Current Meter. — In addition to 

 the current meter itself, the following listed 

 accessory equipment is necessary (fig. 9-6). 



Figure 9-6. Buoy-operated Roberts radio current 

 meter. 



1. A Roberts buoy, which is designed to 

 permit a minimum resistance to surface wave 

 action, is constructed to house the power 

 supply transmitter and sequence switch, and is 

 fitted with an antenna and identification lights. 



2. A suitable anchor, usually a 150-pound 

 Danforth type, with ^ie-inch chain or ^-iiich 

 wire rope, depending upon the requirements 

 of the area. 



3. Wire rope, %2-inch diameter of 7 x 7 

 stranded stainless steel with nylon covering, 

 to suspend the meters and electrical cable from 

 the buoy. The nylon covering is necessary to 

 provide minimum magnetic resistance to the 

 meter mechanism. 



4. A compact transmitter, such as Rixon 

 Model 161, capable of transmitting the meter 

 signals over a 15- to 20-mile range from the 

 anchored buoy. 



5. A sequence switch designed to facilitate 

 multiple meter operation from one buoy. 



The switch serves as a selector for three meters 

 suspended from the buoy, giving identification 

 signals and permitting a transmission period 

 for each. 



6. A whip antenna of stainless steel, 96 inches 

 long, fitted with an insulator and supporting bar. 



7. A battery power supply for the system. 



8. A monitoring radio receiver to receive the 

 band width of the crystals used at various meter 

 stations and locations. A National HRO-50 

 has been found satisfactory. 



9. A crystal-controlled oscillator, at the 

 monitor, to permit accurate pinpointing of the 

 desired frequency. 



10. A chronograph, electrically driven or 

 spring wound, depending upon types available. 



11. A break-circuit chronometer, 6 volts. 



12. A relay box, specially constructed, con- 

 taining essentially 2 relays of 1,000 and 10,000 

 ohms. The 1,000-ohm relay serves to isolate 

 the chronometer from the higher powered 

 chronograph circuit whereas the 10,000-ohm 

 relay transposes the audio signal from the re- 

 ceiver to a DC pulse which is supplied to the 

 chronograph to produce graphic representation 

 of current speed and direction. 



9-55 Equipment Check List and Spare 

 Parts Needed for Operation of the Roberts 

 Radio Current Meter. — In addition to the 

 equipment listed in the preceding paragraph, 

 the following check list of necessary equipment 

 and spares for the operation of 10 meters and 

 6 buoys is given. 



1. Hanger, meter, brass (included in meter 

 case) — 10 sets. 



2. Cable, electric, 2 conductor stranded, 

 Tirex 16 Jr. or Navy DCOP-2— 2,000 feet. 



3. Oil, instrument, Esso formula 1191 — 10 

 gallons. 



4. Bearings, impeller, lignum vitae, spares — 

 10 sets. 



5. Parts, meter, spares, in kit — 10 sets. 



6. Tools, tweezers, jeweler's screwdrivers, 

 pins, etc. — 2 sets. 



7. Volt-Ohm-Milliameter, Triplett Model 

 630—2 each. 



8. Electron tubes, spare, as required by 

 various instruction and operating manuals 

 listed in section 10-55 below. 



9. Relays, spare, Sigma 5R lOOOS and 5R 

 10,0008—5 each. 



10. Crystal, RF, selected frequencies — 24 

 each. 



11. Rubber, sponge, for shock mounting in- 

 struments, sheets 36 x 24 x 2 inches — 5 sheets. 



12. Batteries, dry, 1.5-V fil. and light, 

 Burgess 20F or Eveready 740, 32 batteries per 

 set — 15 sets. 



H. O. 607 



97 



