a control line 15 carries a control signal from fm receiver 12 to variable inductor 13 to shift the resonant frequency of the series resonant circuit i e the center frequency of the passband in accordance with the tuning voltage developed in the receiver for controlling the mixing oscillator not shown thus bandpass filter 11 may exhibit a variable attenuation versus frequency curve as shown in fig2 a resonant characteristic curve 16 is exhibited by the filter at a first value of the tuning control signal whereby the center of the passband coincides with the rf signal of interest which is desired to be mixed to the if frequency of the receiver when other signals are tuned in other values of the tuning control signal shift the resonant characteristic as shown at curves 17 19 as shown by all the characteristic curves however a large amount of attenuation is provided in the am frequency band by the series resonant circuit since it is not practical to construct resonant circuits wherein the resonant frequency is variable over a wide enough range to include the am and fm frequency band the prior art receiver shown in fig1 prevents am signals received by the antenna from reaching the receiver therefore am signals cannot be received in receiver 12 unless a separate signal path is provided for am signals the.