| 摘要 |
PURPOSE:To make the reception frequency band equal to each other by connecting plural preset variable resistors having a sufficiently small residual resistance in parallel via a semi-fixed variable resistor of a comparatively large resistance from a main variable resistor having a comparatively large residual resistance. CONSTITUTION:A DC voltage is supplied to an oscillation circuit comprising a coil 1 and a varactor diode (VC) via a resistor 3 and a changeover switch (SW) 7. The SW 7 is thrown to a contact (a), a main variable resistor (MVC4) is adjusted to obtain a position from which a maximum and a minimum voltage are applied to the VC 2. Comparatively large residual resistances 4a, 4b are connected to the MVC 4. Then the SW 7 is thrown to a contact (b), a preset variable resistor (PV) 5 having a small residual resistance is adjusted to generate a maximum voltage, and a semi-fixed variable resistor 8 having a comparatively large resistance is adjusted to produce the same maximum voltage as that for the MVC 4. Then the PV 5 and the semi-fixed variable resistor 9 are used to obtain a minimum voltage equal to that of the MVC 4. The similar adjustment is applied to the PV 6. Thus, the width of the reception frequency band is arranged.
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