14 



OCEAN ELECTRONIC NAVIGATIONAL AIDS 



operating the Loran transmitter and similar timing piilses for other secondary 

 station functions. 



Some idea of the high degree of precision of the Loran timer equipments 

 may be illustrated by the fact that a pocket watch of comparable accuracy 

 would run for a period of over 9^/2 years before it would lose or gain a single 

 second of time. 



A third item of equipment which is of fundamental importance in a trans- 

 mitting station is the Loran switch gear. This is constructed as a separate 

 physical unit and contains the necessary switching equipment to permit the 

 operator to place different units of the station equipment in use by properly 

 connecting them to the other units. The switch gear chassis also houses the 

 "attenuator" unit, an electronic switch which effectively disconnects the 



Figure 1-12. — Loran station — men on watch at the timing equipment. 



receiver unit each time the local transmitter sends out a signal. It is neces- 

 sary to do this to prevent the receiver from being damaged by the strong 

 signal that is generated in the vicinity of the station's own transmitting 

 antenna. During the interval when the local transmitter is not sending out 

 a signal, the "attenuator" reconnects the receiver to permit the operator to 

 receive the signal from the distant station. 



In order to provide reliable Loran service even in the case of minor failures 

 of equipment it is the established practice in equipping Loran stations to 

 provide duplicate units of all of the major items. In this manner an equip- 

 ment failure causes only a momentary pause in the service, since the stand-by 

 equipment can usually be placed in service in less than a minute's time. 



Figures 1-10, 1-11, and 1-12 illustrate transmitting station equipment and 

 installation layout plan. 



LORAN SYSTEM DESCRIPTION 



(Note. — The technical aspects of the Loran system are described in this 

 section for purposes of completeness, to be used for the information of persons 

 who may have occasion to study Loran in some detail. The material pre- 



