18 BELL SYSTEM TECHNICAL JOURNAL 



of about ±200 yards was then considered very usable in surface target 

 fire control. The target azimuth could also be determined to a precision 

 of one or two degrees by rapidly swinging the antenna back and forth and 

 observing the point which gave a maximum echo signal. This angular 

 information was hardly good enough for fire control use. The equipment 

 was also of some use against low flying aircraft as a means of getting better 

 range data for fire control. Minor equipment difficulties were not entirely 

 solved; in particular the doorknob triodes in the transmitter had a very 

 short life under the high voltage pulse operating conditions. They had, of 

 course, been designed originally for CW communication use and strenuous 

 development effort to make them more suitable for the intermittent high 

 power radar use had not been very successful. 



The Mark 1 Radar 



In spite of the obvious unsolved development problems the Navy im- 

 mediately ordered 10 equipments, similar to the CXAS, for use in the 

 Fleet. These were first called the FA Radio Ranging Equipment but the 

 designation was later changed to Radar Mark 1. Several changes were 

 made to better adapt the equipment for installation aboard ship, the princi- 

 pal one being a servo driven antenna pedestal of the amplidyne type which 

 was furnished by the General Electric Company. The servo system elim- 

 inated the antenna drive shaft problem while retaining control from a 

 handwheel on the control desk. The desk was also modified to provide 

 dials reading both relative and true azimuth bearing, the latter being ob- 

 tained by interconnection with the ships gyro compass system. 



The first Mark 1 Radar was shipped by the Western Electric Company 

 in June 1941 and installation on the USS Wichita was completed at the 

 Brooklyn Navy Yard early in July 1941. This was the first fire control 

 radar in our Fleet and the first of many thousands of radars of all types 

 which the Western Electric Company was destined to build for the Navy 

 in the following four years. 



The Mark 2 Radar 



While the ten Mark 1 radars were being built, development work was 

 proceeding at top speed on major improvements designed to increase per- 

 formance, eliminate operating troubles, and to make this new device fit 

 better into the existing Hre control situation aboard ship. The older opti- 

 cal devices were neatl}- integrated into a S}-stem, many features of which 

 were automatic. For exami^le, the gyro stabilized telescopes and optical 

 range finder were assembled into a compact rotating armored box called a 

 director, located high on the ship. Target data from the director was sent 



