562 BELL SYSTEM TECHNICAL JOURNAL 



and external views of Figs. 63 and 67. On one side of the tube a strut extend- 

 ing from the base is attached to the repeller housing. This strut acts as a 

 rigid vertical support but provides a hinge for lateral motion. On the 

 oppos'te side the support is provided by a pair of steel strips. These are 

 clamped together where they are attached to the vacuum housing support 

 and also where they are attached to a short fixed strut near the base. A 

 nut is attached rigidly to the center of each strip. One nut has a right and 

 the other a left handed thread. A screw threaded right handed on one half 

 and left handed on the other half of its length turns in these nuts and drives 

 them apart. The mechanism is thus a toggle which, through the linkage 

 provided by the repeller housing, serves to move the grids relative to one 

 another and thus to provide tuning action. 



The 723A/B was originally designed for a relatively narrow band in the 

 vicinity of 9375 megacycles. It operates at a resonator voltage of 300 volts 

 and the beam current of a typical tube would be approximately 24 milliam- 

 peres. The design was based on the use of repeller voltage mode which 

 with the manufacturing tolerances lay between 130 and 185 volts at 9375 

 megacycles. It is difficult to establish with certainty the number cf cycles 

 of drift for this mode. Experimental data can be fitted by values of either 

 6| or 7f cycles and various uncertainties make the value calculated from 

 dimensions and observed voltages equally unreliable. This value is. how- 

 ever, of interest principally to the designer and of no particular mxoment in 

 application. The performance was specified for the output line cf the os- 

 cillator coupled to a f" x \\" wave guide so that the probe projected full 

 length into the guide through the wider wall and on the axis of the guide. 

 With a matched load coupled in one direction and a shorting piston ad- 

 justed for an optimum in the other the oscillator was required to deliver a 

 minimum of 20 milliwatts power output at a frequency of 9375 megacycles. 

 Under the same conditions the electronic tuning was required to be at 

 least 28 megacycles betw^een half power points. 



For reasons of continuity a more detailed description of the properties of 

 the 3 centimeter oscillator will be given in a later section. The 723A/B 

 oscillator served as the beating oscillator for all radar systems operating 

 in the 3 centimeter range until late in the war when the 2K25 supplanted 

 it. At the time that the 723A/B was developed the best techniques and 

 equipment available were employed. In retrospect these were somewhat 

 primitive and of course this resulted in a number of limitations of per- 

 formance. Since the tubes designed as beating oscillators commonly 

 served as signal generators in the development of ultra-high frequency 

 techniques and equipment the wartime designer of such oscillators usually 

 found himself in the position of lifting himself by his own bootstraps. In 

 spite of these limitations the later modifications of the 72v3A/B which led to 



