ADVISORY MINIMUM SPECIFICATIONS FOR MANUAL RADIO 

 DIRECTION FINDER EQUIPMENT; TYPE II 



General. — The intent of this minimum specification is to serve as a general 

 guide for use by parties interested in marine direction finding equipment for 

 small craft where personnel, space, and initial cost are important factors. 



Loop. — The loop should be small, watertight, arranged for either inside or 

 outside mounting, and be capable of being completely rotated around its 

 vertical axis. 



Indicator. — The indicator should be as simple as practicable and still give 

 accurate bearing information. The device should be capable of being read 

 to within 1° of circular arc. No mechanical compensation is required. 

 Provisions should be made to provide a calibration card located readily avail- 

 able to the operator. 



Receiver Circuits. — Tuned radio frequency or superhetrodyne capable of CW 

 or MCW reception. 



frequency. — 275 to 340 kc. 



Over-all Sensitivity. — The Complete unit including loop assembly should be 

 capable of developing an output of 6 milliwatts, with not more than 60 micro- 

 watts noise output, when the loop is rotated for maximum signal in a ground 

 wave field strength of 50 microvolts per meter. 



Cabinet. — The Cabinet size should be kept small, be spray-proof, and designed 

 in accordance with standard practice for shipboard electronic equipment. 



Power Requirements. — The equipment should be designed principally for battery 

 operation, with the use of converter equipment at the option of the user 

 desiring to use it on other power supplies. 



ADVISORY MINIMUM SPECIFICATIONS FOR AUTOMATIC RADIO DI- 

 RECTION FINDER EQUIPMENT 



NOTE. — Because exact engineering and operational requirements for marine 

 automatic direction finding equipment are not available, the United States 

 Coast Guard is not prepared to publish an advisory minimum specification 

 for such equipment at this time. Practical and eflBcient marine ADF equip- 

 ment has been developed for military use. When commercial automatic 

 direction finder equipment is developed for the maritime industry, or when 

 firm requirements for the equipment are established, advisory minimum 

 specifications will be published. 



The United States Coast Guard has converted and is operating for ADF 

 and manual direction finding equipment use 16 marine radiobeacon stations. 

 These stations provide continuous carrier toned keyed (CW signal emitted 

 when station MCW identification characteristic not being transmitted) 

 service. 



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