AUTOMATIC ADJUSTING DEVICE FOR ROD ANTENNA LENGTH OF AUTOMOBILE FM RADIO

摘要

PURPOSE:To exactly perform an automatic adjustment for the rod length of a rod antenna by fitting a frequency for that of an FM broadcast desired to listen, by interrupting an automatic adjusting operation at the time of moving a vehicle during the automatic adjusting operation, and restarting the operation after the vehicle stops. CONSTITUTION:A motor control circuit 8 starts the expanding operation of a rod antenna 1 by the turn on operation of the power source switch of an FM radio 3, or the channel selecting operation of a channel selection knob after the turn on operation of the power source switch at the staying time of the vehicle when no signal is outputted from a travel detector 7, and performs the automatic adjusting operation for a rod antenna length that stops the expanding operation of the rod antenna 1 by the output signal of a peak detector 5. And at the time of moving the vehicle, and outputting the signal from the travel detector 7 during the automatic adjusting operation, the automatic adjusting operation is interrupted, and the rod antenna 1 is expanded to the maximum length of the rod antenna 1, or to 1/4 of the average wavelength of the receiving area of the FM radio 3, and a driving motor 2 is controlled so as to restart an interrupted automatic adjusting operation, at the time of stopping the vehicle, and outputting no signal from the travel detector 7.