FLUCTUATION NOISE IN VACUUM TUBES 



645 



Fig. 3 — Tube under test mounted in the shielding box 



;70 



m 150 



130 



120 



10 



100 1000 10,000 



FREQUENCY IN CYCLES PER SECOND 



SO.OOO 



Fig. 4 — Frequency characteristic of amplifier circuit. Curve A with no filter, Curve 

 B with low pass filter, and Curves C and D with band pass filters. 



