frequency. Automatic frequency control networks integral with the equipment 

 maintain reception which gives continuous positional information at velocities 

 up to about 80 knots. Less accuracy could be expected at hi^er velocities . 



After completing the acquisition each operator switches his unit to the 

 Measure Mode, where the internal program is used to range and display the data 

 automatically. No further operator attention or calibration is required, as the 

 measurement process is fully automatic. In the event of signal interruption the 

 measurement process automatically resumes when the signals are again available. 



d. Auxiliary Output 



An auxiliary data output is provided as a 20-line binary coded decimal 

 format which is compatible with standard data processing equipment. For in- 

 shore operation, a special design accessory plotter is available. This plotter 

 uses the two Interrogator ranges and converts them to an x-y plot for any pre- 

 set base line. Intermediate equipment is required for conversion of BCD to 

 an analog input to the plotter . 



e. Power Requirements 



The Autotape system is intended as a portable system. The Responders 

 are tripod-mounted and require 36 watts at 12 v dc . The two- range Interrogators 

 are table top-mounted and require 72 watts at 12 v dc. The radiated power out- 

 put of the Interrogator and Responder is approximately 200 mw. 



3. ACCURACY 



Two classes of error are inherent in the Autotape system, systematic 

 and random. 



a. Systematic Errors 



The systematic errors can be quite accurately determined and in 

 many cases eliminated. Errors due to variations in the propagation velocity of 

 rf energy and those due to reflection and refraction are in this group. 



An instrumental accuracy of 50 cm is achieved with omnidirectional 

 antennae at both the Interrogator and Responder sites at ranges out to 25 km, 

 provided line-of-sight transmission is maintained. The phase measurements 

 are converted directly to meters for an average index of refraction of 320N 



146 



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