26 



BELL SYSTEM TECHNICAL JOURNAL 



where n = 1,2, 3. — etc., L is the length of the beam and V the driving 

 potential. 



In this method there is less disturbance from gas focusing and space 

 charge if the filament current is made as low as will give a still visible 

 spot with the magnetic focusing. 



MAY \a '" 1935 



• AMPLIFICATION RATIO 15 I PERIOD 0937-0942 G.M.T. 



"AMPLIFICATION flATIO 10 PERIOD 0943-0948 &.M.T, 



3 AMPLIFICATION RATIO 5 I PERIOD 0949-0954 GMT 



Fig. 36 — Azimuthal distribution of atmospherics.-' 



From the beginning the cathode ray oscillograph was recognized as 

 a tool of great promise. Its use w^as limited, however, by the diffi- 

 culties of maintaining a constant degree of vacuum and of providing a 

 suitable source of high voltage, as well as by the general bulk and 

 clumsiness of the apparatus. We have seen that in the nearly thirty- 

 five years since the first invention of the tube, many improvements 

 have been made both in the structure of the tube and in the methods 



■'nVatson Watt and Herd, Jl. L E. E., 64, p. 611, 1926. 



