The L3 Coaxial System: Amplifiers

THE L3 SYSTEM -- AMPLIFIERS 881 greater precision than we can economically control the individual. This is exactly the effect which modern methods of statistical quality control aim at achieving, and since the entire amplifier is merely the sum of its parts, quality control must start at the roots of the manufacturing process. In order to apply quality control intelligently, and to be sure that all important causes of gain variation are understood, it has been necessary to carry out, side by side with empirical laboratory work, a program of computing the insertion gain of the amplifier, starting with fundamental element values. These computatuions have also proven of value in obtaining satisfactory stability margins in the design of the low and high frequency cut-offs of the feedback loops, and in obtaining preliminary information on amplifier gain deviations for use in equalization planning. The severe gain and delay reproducibility objectives also have their effect 011 the mechanical design of the amplifier. At first sight the unit appears to be a lumped constant structure rather than one in which distributed effects would be of paramount importance. Usually the circuit designer in such a case is interested in the mechanical design only for reasons of neatness and economy, but when we look deeper we find that in the amplifier structure as a whole as well as in the case of certain components, the effects of distributed capacity and inductance could easily defeat our objectives if the mechanical design were not such as to assure precise control of element placement and wiring lengths.