60 OCEAN ELECTRONIC NAVIGATIONAL AIDS 



Resolution: 

 A properly designed Radar with pulse length and antenna beam 

 width as elsewhere prescribed in this specification brief should give a 

 range resolution of 100 yards and a bearing resolution of 4° on the 

 shortest sweep scale. 



V. Indication and Outvut Data — 

 Indicator: 



At least 7 inch PPI scope (plan position indicator) . 



Sweep linearity shall not deviate more than ±2 percent except that 

 the first and last 10 percent of the sweep may deviate by ±5 percent. 

 Range scales: 



Capable of being set as desired by purchaser within the following limits: 

 2-5 miles; 4-15 miles; 15-30 miles; a positive range scale indicator 

 is to be provided. 

 Range indicator: 



A variable range marker with a range of 500 yards to 30 miles, accuracy 

 ±2 percent or ±50 yards whichever is greater or a direct reading 

 range indicator. 

 Bearing indication: 



Stabilized PPI presentation (true bearing display), bearing cursor; 

 ship's head indicator; variable azimuth illumination. 



VI. Performance Indicator — 



Positive means should be provided to indicate whether or not the over-all 

 operation of the Radar is such that it may be relied upon to provide effective 

 anticollision and navigational information. 



VII. Antenna — 



Truncated parabola or equivalent. 

 Beam width: 



Horizontal — 4° at half power points. 



Vertical — Such as to prevent the transmitted beam from leaving a target 

 on the horizon during a roll of ±1^2% • To accomplish this the an- 

 tenna may be stabilized or have a vertical beam width of 15° at half 

 power points. 

 Mounting: 



Navy standard flange ilQVz inch bolting circle with eight i%6 inch holes 

 equally spaced, two opposite holes on center line). 

 Rotation: 



Continuous, 360° in azimuth, speed of rotation 6 to 15 revolutions per 

 minute; control on main on-oflf switch. Antenna reversing switch 

 may be provided to sector scan. 

 Side lobes: 



At least 25 decibels down. 



VIII. Transmitter — 



Frequency recommended — 10-centimeter band, 3000 to 3246 megacycles 

 (see par. XIV) . 



Radio frequency source — Magnetron. 



Modulator — Hydrogenthyratron, hard or soft tube, or equivalent. 



Main transmission line — the over- all attenuation from the radio fre- 

 quency source to the radiator must not be more than 1.5 decibels one 

 way. 



Peak power — 15 kilowatt minimum. 



Pulse repetition rate — Minimum 800 cycles per second. 



Pulse length — 0.5 microsecond maximum. 



Trigger — positive 10 to 50 volts (across high impedance), 



IX. Receiver — 



IP, RF, and video band pass — Optimum for pulse length chosen. 



Over-all gain — 120 decibels minimum. 



Video output — 2.5 volts ±0.5 volt (across 75 ohms). 



Over-all noise above KTAf — 15 decibels maximum. 



Features : 



Automatic frequency control; fast time constant; sensitivity time 

 control or equivalent circuits to give the operator optional control 

 over interference from sea return and adverse meteorological 

 conditions. 



