| 摘要 |
PURPOSE:To prevent the receiver from being affected by noise at the reception of an intermediate wave by grounding apparently a whip antenna at the intermediate band. CONSTITUTION:When short waves SW1, SW2 are received with changeover switches S1-1, S1-2 placed in positions of terminals b, c, no voltage in terms of DC is applied to the movable terminal of the switches S1-1, S1-2. When a middle wave MW is received with the switches S1-1, S1-2 placed in the position of terminal (a), a +B voltage is applied to the movable terminal of the switch S1-2 through the path of resistor R3 coil L1 terminal (a). Further, a voltage is applied to a base of a switching transistor TRQ3 through the path of the movable terminal of the switch S1-2 resistor R5 and a collector-emitter of the TRQ3 is short-circuited apparently. Thus, the effect of the whip antenna 1 is lost and the effect of noise interference on the antenna 1 at the reception of MW is avoided. |
