Abstract: A radio communication apparatus includes a power supply device which includes a solar battery connected to each of a plurality of communication channels via respective switches. A controller constantly monitors the voltage of the solar battery to turn on or off the switches stepwise, so that the number of active channels is reduced stepwise with the decrease in the capacity of the solar battery. The rate of decrease in the capacity of the solar battery is reduced to shorten the period of time during which communication is prevented, whereby operation is insured over a long period of time. Further, communication, (i.e., power consumption) is averaged to reduce the required capacity of the solar battery.