Response of RF Tuned Circuits in Television Tuners at Frequencies FAR from Resonance

Abstract

If the bandwidth of an RF tuned circuit is satisfactory at a few decibels down, it is often assumed that its attenuation continues to increase progressively with further departures from the resonant frequency. That this is not the case for many practical resonant circuits is demonstrated by measurements of the performance of the RF input tuned circuits of several television receivers. Typical variations from simple resonant circuit response are shown to be such as to make the receivers vulnerable to interference from strong signals on freqencies far from the wanted channel. It is suggested that, by giving more attention to the selectivity at frequencies away from resonance, designers will have the possibility of reducing the susceptibility of receivers to certain types of interference.