CONSIDERATIONS INVOLVED IN THE SELECTION AND 

 INSTALLATION OF A MERCHANT MARINE RADAR 



Two factors are most important in selecting a merchant marine Radar: 

 (1) the use to be made of the equipment, (2) the installation problem en- 

 countered on the ship to be equipped. Commercial Radars have been pur- 

 posely designed to be somewhat versatile and some compromises have been 

 necessary. Due, however, to the many factors involved in the design of any 

 Radar equipment, each type offers certain advantages. It is the purpose of 

 the advisory specifications to outline the characteristics considered desirable 

 for various commercial shipboard applications. The following paragraphs, 

 therefore, are intended to point out the considerations involved in the 

 selection and installation of a commercial-type Radar, and to indicate the 

 reasons for some of tlie requirements contained in the advisory specifications. 



RESOLUTION: Owing to the type of presentation on a PPI scope, resolu- 

 tion is divided into two components: resolution in range and resolution in 

 bearing. Resolution in range is the ability to distinguish between two targets 

 on the same bearing and closely spaced in range. (See fig. 4-2.) 



Resolution in bearing is the ability to distinguish between two targets at 

 the same range having slightly different bearings. (See fig. 4-3.) 



RANGE RESOLUTION 



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A PIPS ON SCOPE ARE BLENDED TOGETHER WHEN DISTANCE IN RANriF 

 BETWEEN SHIPS IS LESS THAN DESIGNED RESOLUtIoN FOR RANGE 



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PIPS ON SCOPE ARE TANGENT WHEN DISTANCE IN l?ANGE BETWEEN 

 SHIPS IS THE DESIGNED RESOLUTION FOR RANGE BtlwttN 



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42 



C. PIPS ON SCOPE ARE DISTINCT FOR EACH SHIP WHEN DISTANCE APART 

 IN RANGE IS GREATER THAN DESIGNED RESOLUTION FOR RANGE 



FiGDBB 4-2. — Range resolution. 



