REFLEX OSCILLATORS 



573 



'not the plane of the grids of the oscillator but is instead a more accessible 

 reference plane external to the tube, in this instance the plane through the 

 wave guide perpendicular to its axis which includes the tube probe. It will 

 be observed that the sink margin in the case illustrated was equal to 5.5. 

 At the frequency at which this diagram was obtained, the minimum sink 

 margin permitted by the test specification is 2.5. The variation in this 

 margin results from a variety of causes. As shown in Section III the sink 

 margin is determined by the ratio of the total load conductance to the small 

 signal electronic conductance. The total load conductance consists of the 



U 0.734" >| 



. 1 M 



SECTION ON A-A 



Fig. 70. — A broad band coupling designed to connect the 2K25 to a 1" x §" wave guide 



conductance representing the resonator losses and the conductance arising 

 from the wave guide load transformed through the coupling system. Hence, 

 the coupled load will be subject to variations in the loop dimensions, the 

 characteristics of the couphng line and the transducer. The resonator loss 

 will differ from tube to tube because of the variation in the heating of the 

 grids and resonator by the electron stream, and there will be variations aris- 

 ing from other causes. The electronic conductance varies from tube to 

 tube primarily because of the spread in beam current and secondarily as a 

 result of such factors as variations in the modulation coefficient of the gaps, 

 non-uniformities in the drift space causing a spread in the transit time and 



