| 摘要 |
PURPOSE:To reduce the number of parts and to obtain a good oscillation, by using a switching circuit for switching capacities as well as a switch for switching bands. CONSTITUTION:When a high band is received, a switch 5 for switching bands is turned on, and the connection point between tuning coils 3 and 4 is grounded, and therefore, capacitors 10 and 9 act as an output terminal capacity of an amplifying element 1. When a low band is received, the capacitor 10 acts for feedback because the switch 5 is turned off. Then, the value of the capacitor 10 is set to a proper value to obtain proper output terminal capacity and feedback capacity of the amplifying element 1 in each receiving band. Since the output terminal capacity and the feedback capacity of the amplifying element 1 are switched to optimum values for each receiving band without using a private switching circuit, a good local oscillating circuit with a small number of parts is obtained. |
