| 摘要 |
PURPOSE:To satisfactorily cover the entire width of an AM band without deteriorating the receiving sensitivity by adding an inductance circuit for correction of tracking correction which is controlled by a switching circuit working with the channel selection voltage to a parimary tuning circuit. CONSTITUTION:When the channel selection voltage Vt drops down to 4, 5V, a 1st switching circuit 8a is opened and a 1st additional coil 7a is connected in series to a tuning coil 3. When the voltage Vt drops down to 3V, a 2nd additional coil 7b is connected in series to the coil 3 and an inductance L2 is added. Thus the inductance of a primary circuit 1 is varied in steps in a range of low receiving frequencies. This fact is equal to a case where the varying rate of synthetic capacity has apparently big change in the range of low receiving frequencies. Thus the synthetic capacity characteristics are improved rectilinearly and smoothly in said range.
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