RADIO RECEIVER

PURPOSE:To improve easily radio interference characteristics, by controlling automatically band characteristics of a ceramic filter for intermediate frequency, so that it becomes a narrow band and a wide band when a disturbing wave exists and when it does not exist, respectively. CONSTITUTION:When a disturbing wave, etc. do not exist, output amplitude of a wide band amplifier 10 connected from a part of a high-frequency amplifier 2 is small, rectifying voltage by a diode 11, which is inputted to the base is also small, therefore, a transistor 13 is not driven, and accordingly, the transistor 13 is in a cutoff state, the collector potential rises, and a transistor 16 becomes a conducting state. That is to say, a capacitor 18 is connected in parallel to a coupling capacitor 17 of a ceramic filter 5, and a band of intermediate frequency becomes a wide band. Subsequently, when a radio receiver receives a disturbing radio wave distant from a desired station, the output amplitude of the wide band amplifier 10 increases, the capacitor 18 is detached from the coupling capacitor 17, a passing band of the ceramic filter 5 becomes a narrow band, and the disturbing radio wave is eliminated.