542 BELL SYSTEM. TECHNICAL JOURNAL 



. The total electronic tuning between half-power points at optimum load- 

 ing, 2(A/)i , can be expressed 



2(A/)j = (fye/M)(2AWo,o)/(ye/M). (10.15) 



We can obtain (2Aw/coo)/iye/M) from Fig. 16. 



If we assume a circuit consisting of a constant inductance L and a capaci- 

 tance, the characteristic admittance of the resonator is 



M = 1/coL = Itt/iPF (10.16) 



and 



2(A/)i = 27rWJ,'LyX2AW^o)/(ye/M) (10.17) 



and we have 



ye = /327o(2xAO/2Fo . (10.18) 



Here A^ is the total drift in cycles. 



A rough calculation estimates the resonator inductance of the 2K25 as 

 .30 X 10~ henries. Using the values previously assumed, /o = (.53)(.026), 

 Fo = 300, N = 7f , and the values of Gulyc^"^ and j\ previously assumed, 

 we can obtain electronic tuning. 



A curve for half power electronic tuning vs TF has been computed and is 

 shown in Fig. 55, together with experimental data for a 2K25. The experi- 

 mental data fall mostly above the computed curve. This could mean that 

 the inductance has been incorrectly computed or that the drift effectiveness 

 is increased over that for a linear drift field, possibly by the effects of space 

 charge. By choosing a value of the drift effectiveness factor other than 

 unity we could no doubt achieve a better fit of the electronic tuning data 

 and still, by readjusting Gg\ and Gs\ , fit the power data. This whole pro- 

 cedure is open to serious question. Further, it is very hard to measure such 

 factors as Ggx for a tube under operating conditions, with the grids heated by 

 bombardment. Indirect measurements involve many parameters at once, 

 and are suspect. Thus, Figs. 54 and 55 are presented merely to show a 

 qualitative correspondence between theory and experiment. 



XI. Noise Sidebands in Reflex Oscillations 



In considering power production, the electron flow in reflex oscillators 

 can be likened to a perfectly smooth flow of charge. However, the discrete 

 nature of the electrons, the cause of the familiar "shot noise" in electron 

 flow engenders the production of a small amount of r-f power in the neigh- 

 borhood of the oscillating frequency — "noise sidebands". Thus the energy 

 spectrum of a reflex oscillator consists of a very tall central spike, the power 

 output of the oscillator, and, superposed, a distribution of noise energy 

 having its highest value near the central spike. 



