FIRE-CONTROL RADARS IVR .V.Il'.lL VESSEL 19 



automatically by synchro data transmitters to the computer below decks, 

 wliich solved the fire control problem and likewise transmitted automatically 

 the correct information to the guns. For the new radar target locating 

 device to fit into the existing system it was necessary to make its angle 

 finding function operate more in the manner of the telescopes. Not only 

 was it desired to determine target angles more accurately but it was nec- 

 essar}' to track target position continuously and smoothly. Finally, to 

 take care of the anticipated need for rapidly changing back and forth during 

 an engagement from optical to radar data it became apparent that the 

 same operators should handle both jobs. Thus it was decided that the 

 system should provide the existing operators with oscilloscopes to sup- 

 plement their telescopes, and to arrange them so either could be used as 

 desired. Further to coordinate the data it became obvious that the radar 

 antenna should be connected with the optics in such a way that the two 

 were always pointed in the same direction. This would make it possible 

 to leave the existing data transmission system alone and would avoid any 

 break in data when changing from optics to radar or vice versa. For 

 example, if a visible target disappeared behind a fog bank the telescope 

 operator would simply move his head to look at his oscilloscope and data 

 would continue to flow smoothly to the computer and to the guns. 



Thus the engineers of the Navy decided the new radar device could be 

 fitted into the existing fire control system. Any other decision would 

 likely have required modification of many parts of the system, and would 

 have delayed the extensive use of fire control radar by a matter of years. 

 The Bell Telephone Laboratories were accordingly asked to modify and 

 improve the radar design to make possible the coordination of optics and 

 radar as just discussed. The new radar was to be called Mark 2 and was 

 to be similar to the Mark 1 but modified to provide continuous tracking in 

 azimuth with an accuracy of ±15 minutes of arc, and continuous tracking 

 in range with an accuracy of ±50 yards. Further, the operator's oscil- 

 loscopes and controls were to be put into small units that could be mounted 

 alongside of the telescopes in the director, and the antenna was to mount 

 on the director. These requirements demanded some important forward 

 steps in radar development which will be described in some detail. Before 

 Radar Mark 2 got into production a much higher powered transmitter was 

 developed and with this change the equipment was re-named Radar 

 Mark 3. 



The Mark 3 Rad.ar 



The general arrangement of apparatus for this radar differed from the 

 Mark 1 principally in the indicators, which were designed to mount in the 



