REFLEX OSCILLATORS 463 



The first part of this paper attempts to give a broad exposition of the 

 theory of the reflex oscillator. This theoretical material provides a back- 

 ground for understanding particular problems arising in reflex oscillator 

 design and operation. The second part of the paper describes a number 

 of typical tubes designed at the Bell Telephone Laboratories and endeavors 

 to show the relation between theory and practice. 



The theoretical work is presented first because reflex oscillators vary so 

 widely in construction that theoretical results serve better than experi- 

 mental results as a basis for generalization about their properties. While 

 the reflex oscillator is simple in the sense that some sort of theory about it 

 can be worked out, in practice there are many phenomena which are not 

 included in such a theory. This leaves one in some doubt as to how well 

 any simplified theory should apply. Multiple transits of electrons, different 

 drift times for different electron paths and space charge in the repeller 

 region are some factors not ordinarily taken into account which, neverthe- 

 less, can be quite important. There are other effects which are difficult to 

 evaluate, such as distribution of current density in the beam, loss of elec- 

 trons on grids or on the edges of apertures and dynamic focusing. If we 

 could provide a theory including all such known effects, we would have a 

 tremendous number of more or less adjustable constants, and it would not 

 be hard to fit a large body of data to such a theory, correct or incorrect. 



At present it appears that the theory of reflex oscillators is important in 

 that it gives a semi-quantitative insight into the behavior of reflex oscilla- 

 tors and a guide to their design. The extent to which the present theory 

 or an extended theory will fit actual data in all respects remains to be seen. 



The writers thus regard the theory presented here as a guide in evaluating 

 the capabilities of reflex oscillators, in designing such oscillators and in 

 understanding the properties of such tubes as are described in the second 

 part of this paper, rather than as an accurate quantitative tool. Therefore, 

 the exposition consists of a description of the theory of the reflex oscillator 

 and some simple calculations concerning it, with the more complicated 

 mathematical work relegated to a series of chapters called appendices. 

 It is hoped that this so organizes the mathematical work as to make it 

 assimilable and useful, and at the same time enables the casual reader to 

 obtain a clear idea of the scope of the theory. 



I. Introduction 



An idealized reflex oscillator is shown schematically in Fig. 1. It has, 



of course, a resonant circuit or "resonator."^ This may consist of a pair of 



grids forming the "capacitance" of the circuit and a single turn toroidal 



1 For a discussion of resonators, see Appendix I. It is suggested that the reader consult 

 this before continuing with the main work in order to obtain an understanding of the circuit 

 philosophy used and a knowledge of the symliols employed. 



