63 STAT.] MULTILATERAITELECOMIUITJNICATIONS-OCT. 2 , 1947 (Chaetw I art. I RR) (66-71) 66 Coefficient of Directivity of an Antenna: The coeffi- cient of directivity of an antenna " in a given direction is the ratio, expressed in decibels, of the square of the field intensity radiated in this direction to the mean of the squares of the field intensity radiated in all directions in space, where the fields are measured at a distance sufficiently great. Directivity Diagram of an Antenna: 67 a) The directivity diagram of an antenna is the graphical representation of the gain of this an- tenna in the different directions of space. 68 b) The horizontal directivity diagram of an antenna is the representation of the gain in the different directions of a horizontal plane or, if necessary, in the different directions of a plane slightly in- clined to the horizontal. 69 Harmful Interference: Any radiation or any induc- tion which endangers the functioning of a radionavigation service or of a safety service 2) or obstructs or repeatedly in- terrupts a radio service operating in accordance with these Regulations. Section V. Systems and Equipment 70 Instrument Landing System: A system of radionavi- gation, intended to facilitate aircraft in landing, which pro- vides lateral and vertical guidance including indications of distance from the optimum point of landing. 71 Racon: A radionavigation system transmitting, automatically or in response to a predetermined received sig- nal, a pulsed radio signal with specific characteristics. 66.1 ) When not specified otherwise the figure expressing the coefficient of directivity refers to that in the direction of the main beam. When it is not necessary to take into account antenna and earth losses the coefficient of directivity as defined above is 2.16 decibels higher than the gain of the antenna as defined in 65. 69.1 2) Any radio service, the operation of which is directly related, whether permanently or temporarily, to the safety of human life and the safe- guarding of property, shall be considered as a safety service. 81939 0-52-PT. l---20 1595
�
