REFLEX OSCILLATORS 



557 



greater capacitance of a gap with fine grids, so that a larger electronic tuning 

 range is obtained than with an open gap. The successful low voltage 

 operation of the 707A established a precedent which was followed in all the 

 succeeding reflex oscillators designed for radar purposes at the Bell Tele- 



:707 



Fig. 61. — A narrow tuning range cavity for the W.E. 707-A of the t}'pe used in radar 

 systems. The inductance of the cavity can be adjusted by moving screws into it. This 

 view also shows the adjustable coupling loop. 



phone Laboratories. The 707A is required to provide a minimum power 

 output of 25 milliwatts and a half power electronic tuning of 20 megacycles 

 near 3700 megacycles. The power output and the electronic tuning are in 

 excess of this value over the range from 2500 megacycles to 3700 megacycles 

 in a repeller mode having 3f cycles of drift. 



