Aids in the Design of Intermediate-Frequency Systems

A set of design curves has been developed by means of which the over-all selective performance of an intemediate-frequency amplifier may be predicted with the expenditure of little time or effort. The design chart is based on identical circuits, but with the appropriate conversions, variations in circuit Q can be accommodated readily by determination of the equivalent identical circuits. The design method permits a prediction of the allowable spacing between equal desired and undesired signals in the frequency spectrum to maintain the desired signal within 6 decibels of resonant output and the undesired signal at more than 60 decibels below resonant output, when variations in frequency due to such causes as modulation, drift, and setting are taken into account. Methods of arriving at a rapid approximation to the over-all curve, in those cases in which circuits of different coupling are cascaded, are discussed.