58 OCEAN ELECTRONIC NAVIGATIONAL AIDS 



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. 

 Bsam width: 



Horizontal — 2° maximum at half -power points. 



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

 target on the horizon during a roll of +7y2°. To accomplish this 

 the antenna may be stabilized or have a vertical beam width of 15° 

 at half-power points. 

 Mounting: 

 Navy Standard Flange (16 V^ 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 with the specified transmitter and modulator characteristics. 

 In the event a higher speed of rotation is desired, peak power and 

 other characteristics of the modulator and transmitter should be 

 raised sufficiently to compensate for a decreased return due to fewer 

 "hits" per revolution of the antenna. Control on main on-off switch. 

 Antenna reversing switch may be provided for sector scan. 

 Side lobes: 

 At least 25 decibels down. 



VIII. Transmitter. — 



Frequency recommended — 3 centimeter band, 9320 to 9430. 

 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 3 decibels one way. 

 Peak power — 15 kilowatts 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. — 



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



Over-all gain — 120 decibels minimum. 



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



Over-all noise above KTA — 15 decibels maximum. 



Features: 



Automatic frequency control; fast time constant; sensitivity time 



control or equivalent circuits to minimize interference from sea 



return and adverse meteorological conditions. 



X. Power Requirements. — 



The equipment shall be designed to take power from a source of 115 volts, 

 60 cycles per second, single phase with a regulation of ±10 volts and ±2 

 cycles per second. In the case of direct-current equipped ships and ships 

 with poor regulation, auxiliary power equipment will be necessary. 

 XL Operator Controls. — 

 On-off switch (all power) . 

 Bearing cursor knob. 

 Range marker knob. 

 Continuous gain control. 



Limited intensity control ; focus to be essentially independent of intensity. 

 Range selector (positive range scale indicator) . 



STC, FTC selector switch for varying degrees of any or all (sea return 

 and interference suppressor) . 



