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BELL SYSTEM TECHNICAL JOURNAL 



remains centered as the range unit phase shifters are rotated thus causing 

 all of the signals (rather than the notch) to move across tlie screen. Range 

 measurement is made by rotating the range unit handcrank to place the 

 desired signal in the center of the range notch on the indicator. This 

 type of presentation has several advantages. It permits the full 100,000-yard 

 range to be viewed at all times so that new targets may be immediately 

 detected, and permits accurate viewing of the desired target in the expanded 



Fig. 27 — Mark 6 ik. 4 — Range presentation 



center of the sweep where best focus is obtained. For smooth range track- 

 ing it is only necessary for the operator to rotate the range unit hand crank 

 to keep the desired signal centered in the range notch. 



A block diagram of the range measuring system, together with the circuits 

 used to obtain the cathode ray indicator presentation described above, is 

 shown in Fig. 28. A base or reference oscillator generates a sine wave of 

 1.639 kc, one cycle of which corresponds to a radar range of 100,000 yards. 

 This wave, after amplification, is applied to a non-Hnear coil pulse gene- 

 rator' which generates short pulses (one positive and one negative pulse 



^ "Magnetic Generation of a group of Harmonics," E. Petersen, T. M. Manlev L R 

 Wrathall— August 1937, B. 5. r. 7., October 1937. 



