| 摘要 |
PURPOSE:To ensure the characteristic against one signal disturbance represented in image disturbance and to improve the disturbance characteristic at AM high input signal by connecting a resistor for attenuating AM signal so as to be connected in parallel with an AM tuning coil. CONSTITUTION:In throwing a changeover switch 15 to the position of contact (b) in case of the attenuation of an AM signal in the AM reception state, the resistor 14 for attenuating AM signal is connected in parallel with the AM tuning coil 12, the tuning output Q of the coil 12 is decreased and the AM signal is attenuated. Since an FM tuning capacitor 10 constituting a part of a tuning capacitance of an AM tuning circuit 8 is connected through a resistor 13 for attenuating FM signal, there is a shift in AM tuning frequencies, but the shift is included within a practical tuning range by decreasing the Q of the circuit 8 and it is not necessary to readjust an antenna tuning trimmer. The antenna input attenuator where no antenna tuning frequency is changed is obtained with less number of components and the disturbing characteristic at high input signal is improved without deteriorating one-signal disturbing characteristic represented in the image disturbance.
|
