A quantitative study of regeneration by inductive feed back

The use of inductive coupling between the tuned grid circuit and plate circuit of a radio-receiving circuit network employing an electron tube has been extensively used for the amplification of received signals since its discovery by K. H. Armstrong. Using simple alternating-current theory this paper shows that the amplification produced by this type of regeneration in an amplifying circuit network can be considered as being caused by a reduction in the resistance of the tuned circuit. The current amplification produced in the tuned circuit for any value of impressed radiofrequency signal is = Ri {R ~ a)-c^r2 where R x is the resistance of the tuned circuit, M is the mutual inductance which produces the feed back, n the voltage amplification factor of the tube , R2 the total resistance of the plate circuit, C 1 the capacity in the tuned circuit across which the tube is connected, a the reduction in resistance produced by the capacitive feed back through the tube. The voltage of the grid was assumed to be negative at all times. The above equation was completely confirmed by experiment. The current in the tuned circuit with and without regeneration was measured by means of an electrontube voltmeter which measured the drop of potential across the capacity C l in the tuned circuit. The reduction in resistance a caused by capacitive feed back was obtained experimentally by the resistance variation method. CONTENTS. Page,