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Multiple-Tuned Circuits

Double hump resonance was obtained with higher-than-critical coupling in the circuit of Fig. 172. Frequency response with more humps is obtainable if there are more than two coupled loops. Such circuits are more difficult to tune and adjust than the circuit of Fig. 172 because of the reaction of each coupled loop on the others. Easier adjustment can be made with successive "stagger-tuned" band-pass amplifiers. Each amplifier stage is tuned to a slightly different frequency. Because of the isolation of the stages by the associated tubes, tuning one stage does not influence the tuning of another.

Frequency response similar to that of multiple-tuned coupled circuits may be obtained by iterative ladder filter sections. In other words, it does not matter whether the coupling is inductive or capaci-tive; the same shape of response is obtained from the same number of circuits tuned in the same manner. Since similar results are obtained from coupled circuits and filters, the choice between them may be made on the basis of convenience or cost. Considerable literature has accumulated concerning the design and adjustment of multiple-tuned circuits, and special techniques have been developed for tuning them.(1)

(1) See "Alignment and Adjustment of Synchronously Tuned Multiple Resonant Circuit Filters," by M. Dishal, Proc. I.R.E., 89, 1448 (November, 1951).

Last Update: 2011-02-17