| 摘要 |
PURPOSE:To constitute can electronic tuning radio receiver at low cost by supplying a bias voltage of every band to parallel-connected varactor diodes for the band switching of a radio receiver which is tuned by a series resonance circuit. CONSTITUTION:When a long wave reception band LW and a middle wave reception band MW are switched to select the MW, a transistor (TR)Q1 is turned on to short-circuit a coil L2. Further, when the band MW is selected, a bias voltage is applied to a terminal MW+ and applied to a varactor diode D2 connected in parallel to a varactor diode D1 through a variable resistor RV1, diode D3, and resistance R3. When the LW is selected, the TRQ1 is turned off to connect coils L1 and L2 in series, and a voltage is applied to a terminal LW+ and further applied to the D2 through a variable resistance RV2, diode D4, and resistance R3. |
