. The Bell System technical journal . g below cutoff, its exact value of bias being determined by thesetting of a potentiometer control. At the time that the grid signal ampli-tude exceeds this critical cut-off bias value, this tube conducts abruptly as 800 BELL SYSTEM TECHNICAL JOURNAL shown and an output pulse is produced whose position on a time scale isdetermined by the additive phase shift of the timing wave and the setting ofthe pulse selector potentiometer. By mechanically gearing the potentiom-eter and phase-shifting condenser, the final rotation of the control shaft willresult in an o
. The Bell System technical journal . g below cutoff, its exact value of bias being determined by thesetting of a potentiometer control. At the time that the grid signal ampli-tude exceeds this critical cut-off bias value, this tube conducts abruptly as 800 BELL SYSTEM TECHNICAL JOURNAL shown and an output pulse is produced whose position on a time scale isdetermined by the additive phase shift of the timing wave and the setting ofthe pulse selector potentiometer. By mechanically gearing the potentiom-eter and phase-shifting condenser, the final rotation of the control shaft willresult in an output pulse whose delay will increase uniformly and correspondto 2000 yards per revolution of the control. Further amplification is fur-nished in the output amplifier shown. Figure 67 illustrates the final equipment features of a phase-shifting typeof variable range unit as developed for naval vessel radar system will be observed that this unit is mechanically interchangeable with theliquid range unit shown in Fig. RELATIVE PHASEOF INPUT VOLTAGE ECCENTRICROTOR RINGSTATOR EQUIVALENTCIRCUIT Fig. 66.—Schematic outline of operation of phase shifter condenser. In this model, the parallel resonant timing wave oscillatory circuit ismaintained at a constant temperature by employing an electrically heatedoven. Measurements made on this design indicate that the range shifterror to be expected for a warm-up period of 6 minutes was .003% or 15yards at 45,000 yards range. After 6 minutes time, thermal equilibrium isreached and the total range error will be less than 20 yards at 45,000 yardsrange. The unit here illustrated has been universally employed in themajority of naval vessel fire-control radar systems of the past war and thesebasic circuit principles have served for range measurement in other apj^li-cations including precision radar bombing. Automatic Frequency Control and Atitomalir Gain \ Automatic Frequency Control The automatic frequency contr
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