| 摘要 |
PURPOSE:To make it possible to execute the automatic tuning easily and inexpensively, by counting a tuning point detecting output in the vicinity of the tuning point of each broadcasting radio wave by the divider, and stopping a DC detecting output which is applied to the electric charging and discharging circuit for controlling the local oscillator, in case a fixed dividing ratio output has been generated. CONSTITUTION:The numerical value (for instance, ''3'' in case of channel 3) corresponding to the channel of a desired rank is set to the divider 12 by the channel selection switch 14. Subsequently, FF13 is set by operating the start switch 15, at the same time the reset switch 18 is closed, the electric discharging circuit 17 discharges the voltage of the voltage holding device 20 through the addition point 19, and the initial voltage is set to the varactor 3. When the switch 18 is closed after a fixed time has passed, the voltage supplied to the varactor rises gradually, and the frequency is gradually swept, as well. In this state, a pulse corresponding to number of the broadcasting station is supplied to the divider 12 through the inverter 11, and when it conforms with the numerical value which has been set to the divider 12 in advance, a reset output R is sent out and the sweep is stopped. |
