OCEAN ELECTRONIC NAVIGATIONAL AIDS 



39 



Figure 3-5. — X-band Ramark transmitter. 



the need for coded identification of a particular beacon arise, however, this 

 can eventually be accomplished without too much difficulty. 



It will be appreciated that any beacon for general use must be easily 

 utilized by the surface navigator, and also without appreciable, and prefer- 

 ably no, modification of the user's navigational Radar. This precludes the 

 adoption of any of the several existing responder-type systems which require 

 elaborate and expensive modification or auxiliary equipment before the 

 service may be utilized. 



RACON 



An example of the responder-type beacon is the RACON, which was used 

 extensively during the war by military aircraft. Briefly, beacons of this type 

 transmitted only when called, or interrogated, by coded pulses from the Radar 

 of the aircraft desiring the service of the beacon. When so interrogated, the 

 RACON would reply by sending out a set of coded pulses which would indicate 

 its bearing on the PPI scope of the aircraft's Radar. Also, responding bea- 

 cons of this type provide range as well as azimuth by permitting measure- 

 ment of the elapsed time between the triggering of the beacon and the arrival 

 of its response pulse at the aircraft. 



