64 



HYDROGRAPHIC MANUAL 



Figure 16. — A. Raydist phasemeter. B. Brush re- 

 corder. C. Digital printer. 



system is also available and can be used in 

 launches over a limited distance estimated 

 to be about 35 miles. Two whip antennas 

 may be used, or if duplexing techniques are 

 used only one antenna will be required. The 

 two systems are compatible, that is, any sta- 

 tion in the portable system can be substituted 

 for a like station in the D.M. system. 



Two survey vessels can be served by one 

 pair of ground stations. The limitation on 

 multiple use has not been determined ; how- 

 ever, it may be possible for 3 or 4 mobile 

 stations to operate successfully in conjunc- 

 tion with one pair of ground stations. Mobile 

 stations should not operate simultaneously 

 at distances less than 14. mile from each 

 other. 



3-52 Installation at Red ground station. — 



Two transmitters and a dual receiver are 

 required at the Red station (Fig. 17). One 

 transmitter emits a distance-measuring sig- 

 nal on a frequency which is 200 cycles less 



than half the frequency of the mobile station 

 transmitter. The second transmitter pro- 

 vides a carrier frequency for relaying in- 

 formation. 



The antenna system at the station depends 

 on the range at which the system is to be 

 used. When the 10-watt system is used, or 

 if the 100-watt system is limited to a maxi- 

 mum range of about 50 miles, 35-foot whip 

 antennas may be used. A radial ground 

 plane is required at each antenna having a 

 radius approximately equal to the antenna 

 height. 



When maximum distance is desired, three 

 100-foot tower antennas with 100-foot rad- 

 ial ground planes must be used. If duplexing 

 techniques are used, only two towers are 

 required. As a general rule, duplexing of 

 antennas at any station will reduce signal 

 strength and effective range of the system. 

 The antennas at ground stations should al- 

 ways be approximately 250 feet apart. At 

 the Red station one antenna is required to 

 transmit the C-W signal, one to transmit the 

 carrier frequency signal and one to receive 

 the distance measuring signals. When the 

 antennas are duplexed the latter antenna is 

 placed atop the C-W antenna. The three 

 towers are set up in a straight line with 

 antennas involved in distance-measuring be- 

 ing symmetrical with respect to the point or 

 station from which distances are measured, 

 and the carrier frequency at the center tower 

 over the station. The three-tower system 

 requires that a correction be applied to the 

 Green station distances as described in 3-56. 

 This correction is avoided when duplexed 

 antennas are used and they are placed over 

 the station. 



3-53 Installation at the Green station. — 



One receiver and one transmitter are re- 

 quired at the Green station. Two 100-foot 

 tower antennas with ground planes are re- 

 quired for maximum range. The antenna 

 which receives the distance-measuring sig- 

 nals should be placed on the marked station 

 from which distances are measured. The sec- 

 ond antenna should be about 250 feet dis- 

 tant and is used for transmitting the carrier 



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