| 摘要 |
PURPOSE:To obtain a wide tuning frequency range by forming integrally an antenna and a radio main body and using an antenna tuning circuit as an electronic tuning system using a variable capacity diode, and also, storing an optimum voltage applied said diode at every receiving frequency. CONSTITUTION:A signal processing circuit part extending from a tuning coil 3 to a mixer 14 is coupled directly to an antenna 1. A PLL circuit 19 generates successively a frequency fRF to be received and injects it to a primary coil 31. In this case, the circuit 19 applies a control voltage to a variable capacity diode 51 so that the relation of a local oscillation frequency (fosc) and the frequency fRF, and an IF frequency fIF becomes fosc-fIF=fRF. A control part 22 switches an RF switch 8 in accordance with a receiving band, varies a tuning frequency by applying the control voltage to a variable capacity diode 6 through a memory EPROM 4 with regard to each of the frequency fRF, and said control voltage at the time when the output of a mixer 14 becomes the maximum value is stored in the ROM 4. In such a way, the control voltage for giving optimum tuning in accordance with all the frequencies fRF is stored in the ROM 4.
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