hyperbolic isophase lines, but they do not indicate the pairs of lines to which the 

 readings are related. Thus, the geographic position of the receiving unit rela- 

 tive to the transmitting stations must be known at the start of the hydrographic 

 survey. Each successive half-wave interval must then be tabulated as the receiv- 

 ing station is moved relative to the pattern of the hyperbolic grid. Digital 

 counters mechanically coupled to the phase meters are provided for this purpose. 



4. SUMMARY 



a. Type of System 



(1) Cw phase-difference hyperbolic plot multi-user system. 



(2) Number of shore stations required: 



Alpha: 3 (3 transmitters and 2 receivers required) 

 Beta: 4 (4 transmitters and 1 receiver required) 



(3) Length of base line: 10 - 50 miles. 



(4) Operators required: at ground station and on board ship. 



(5) Transmitter frequency: 1. 75 - 2.5 mc (crystal-controlled, 

 adjustable). 



(6) Shore station power level: 300 watts. 



(7) Shore station transmitting antenna: one -quarter wave dipole. 



(8) Shore station receiving antenna: directional loop. 



(9) Shore station transmission: cw with no synchronization required. 



(10) Shipboard receiving antennas: one-quarter wave dipoles (2). 



(11) Mobile station readout: phase meters (2), red line and green 

 line. Also provisions for driving automatic track plotter, 

 tape punch, digital printer and distance -heading indicator. 



(12) Lane identification: digital counter follows movement from lane 

 to lane. Must be pre-set at known geographic position at the 

 start of survey. 



124 



artbur ZD.littlcJnr. 



