3. EQUIPMENT AND INSTRUMENTS 



65 



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Red Station 



Green Station 



PHOTO BT HASIINGS HATDIST 



Figure 17. — Raydist Red and Green shore station equipment. 



frequency. Whip antennas may be used as 

 in 3-52, or the antennas may be duplexed. 



3-54 Power sources. — Electric power 

 for operation of ground stations, approxi- 

 matly 3 kilowatts, may be obtained from 

 commercial sources, 115-120 volt — 60 cps, or 

 from portable generators at the stations. If 

 commercial sources are used, it is advisable 

 to have a portable generator at each station 

 ready for emergency use in event of a power 

 failure. 



3-55 Range and accuracy of Raydist. — 

 The maximum range at which the D.M. Ray- 

 dist can be used satisfactorily for control 

 of hydrography has not been determined 

 through experience. Strong signals from the 

 Green station have been received at a dis- 

 tance of 225 nautical miles. At the same 

 time signals from the Red station, which 

 was 175 miles distant, were not usable. In 

 this instance the antennas at the Red station 

 were duplexed and signals were not as strong 

 as they were with the three-tower system. 



Raydist signals are subject to interference 

 by skywaves at night if the strength of the 

 skywave signal is greater than that of the 

 groundwave. Skywave contamination may 

 be expected at distances greater than 100 

 miles. This applies to the distance between 

 ground stations as well as the distance of 

 the mobile station from either ground sta- 



tion. Atmospheric conditions will also affect 

 Raydist. Electrical storms near any station 

 or between stations and rain static at any 

 station will frequently affect the lane count. 

 Strong radio communication signals close to 

 a frequency used in the system may interfere 

 with its operation, especially if some sky- 

 wave contamination is present. 



Interference with Raydist signals has the 

 effect of causing the phasemeter dials to 

 show a gain or loss of lanes. These will also 

 show on the brush recorder tape. By keep- 

 ing a close watch on the tape it is possible 

 to detect the gains or losses. The observed 

 values can be corrected accordingly. Gains 

 or losses will be in whole lanes, not frac- 

 tions of a lane. Skywave interference will 

 cause the phasemeter dials to oscillate 

 through an arc which increases with the 

 strength of the wave. A continuous strong 

 skywave signal will cause such erratic opera- 

 tion that it will be impossible to keep track 

 of the lane count and the sounding line 

 must be broken. 



Raydist distance measurements are accu- 

 rate to a few tenths of a lane and accuracy 

 does not deteriorate with distance so long 

 as usable signals can be received. Errors 

 in distance measurements remain constant 

 at any distance except as noted in 3-56. The 

 system does not provide a method of lane 



