B. ALPINE PRECISION NAVIGATION SYSTEM MODEL 430 



1. GENERAL 



The Alpine Geophysical Associates Precision Radar Ranging Unit, 

 Remote Electrical Track Plotter, and X-band Radar Transponding Beacons were 

 developed for short-range precision navigation and ship -positioning problems. 

 This system utilizes, in conjunction with the standard shipboard radar trans- 

 mitter and modulator system the Model 430 precision timing and digital readout 

 equipment. The system is designed to operate with two or more fixed targets, 

 which may be prominent land features, buildings, or markers of known position. 

 Anchored reflector or transponder buoys may also be used. The precision 

 ranging unit is capable of providing accurately timed trigger pulses to the radar 

 transmitter and delay information to the radar PPI to provide for an expanded 

 display. The equipment provides ranging accuracies of ± 80 ft with 99% prob- 

 ability at all ranges to the maximum range of the equipment. 



2. DESCRIPTION 



a. Precision Ranging Unit 



The Alpine Model 428 Precision Radar Ranging Unit is operated in con- 

 junction with standard marine radar equipment such as the Decca D-11 series. 

 The Model 430 provides the precision timing required by utilizing a temperature- 

 controlled crystal oscillator with a frequency accuracy of 1 part in 10' . This 

 is divided down to the repetition rate of the radar by using a series of high- 

 stability multivibrator circuits and selection gates. 



The outputs of the Model 430 are: 



(1) A precision variable range marker fed to the radar display 



(2) A digitally controlled step delay generating 1-mile incre- 

 ments for triggering the radar display 



(3) A radar modulator trigger pulse 



(4) Crystal-controlled markers for internal system calibration. 



The Model 430 will function at ranges of standard radars from 0.75 

 mile to 50 miles. Its maximum accuracy is attained at the minimum ranges 

 indicated on most marine radar equipment. 



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