C138 SAFETY OF LIFE AT SEA 



(d) As far as is practicable, the direction-finding apparatus shall be sc 

 located that as little interference as possible from mechanical or other noisej 

 will be caused to the efficient determination of bearings. 



(e) As far as is practicable, the direction-finding aerial system shall be 

 erected in such a manner that the efficient determination of bearings willj 

 be hindered as little as possible by the close proximity of other aerials^ 

 derricks, wire halyards or other large metal objects. 



(/) An efficient two-way means of calling and voice communication shal 

 be provided between the direction-finder and the bridge. 



(g) All direction-finders shall be calibrated to the satisfaction of the 

 Administration on first installation. The calibration shall be verified by 

 check bearings or by a further calibration whenever any changes are made 

 in the position of any aerials or of any structures on deck which might 

 affect appreciably the accuracy of the direction-finder. The calibration 

 particulars shall be checked at yearly intervals, or as near thereto as possible. 

 A record shall be kept of the calibrations and of any checks made of their 

 accuracy. 



Regulation 12 



Radiotelegraph Installation for Fitting in Motor Lifeboats 



(a) The radiotelegraph installation required by Regulation 14 of 

 Chapter III shall include a transmitter, a receiver and a source of energy. It 

 shall be so designed that it can be used in an emergency by an unskilled 

 person. 



(b) The transmitter shall be capable of transmitting on the radiotelegraph 

 distress frequency using a class of emission assigned by the Radio Regula- 

 tions for that frequency. The transmitter shall also be capable of trans- 

 mitting on the frequency, and of using a class of emission, assigned by the 

 Radio Regulations for use by survival craft in the bands between 

 4,000 kc/s and 27,500 kc/s. 



(c) The transmitter shall, if modulated emission is prescribed by the 

 Radio Regulations, have a depth of modulation of not less than 70 per cent, 

 and a note frequency between 450 and 1,350 cycles per second. 



(d) In addition to a key for manual transmissions, the transmitter shall 

 be fitted with an automatic keying device for the transmission of the radio- 

 telegraph alarm and distress signals. 



(e) On the radiotelegraph distress frequency the transmitter shall have 

 a minimum normal range (as specified in paragraph (.?) of Regulation 9 of 

 this Chapter) of 25 miles using the fixed aeriaL* 



• In the absence of a measurement of the field strength, it may be assumed that this range 

 will be obtained if the product of the height of the aerial above the water line and the aerial 

 current (R.M.S. value) is 10 metre-amperes. 



Ch. 4 



