An array of solar batteries for use as the power source of unattended u.h.f. repeaters has recently been established at the top of Mt. Shinobu in Fukushima Prefecture. The equipment consists of two pairs of transmitter-receivers, each of which is partly transistorized. The entire equipment takes approximately 4.5 watts.The silicon solar batteries are used to convert solar energy directly into electrical energy to feed the equipment and simultaneously to charge a set of nickel-cadmium batteries in a floating circuit arrangement as a provision for unfavourable weather.After a series of careful investigations, it became clear that to keep the equipment operating during a long rainy season such as prevails in the Fukushima area, the total capacity of the solar batteries must be designed to be ten times the power actually consumed by the entire equipment. Consequently, the maximum output available from the solar batteries was designed to be about 70 watts. A total of 4320 units were connected to generate 6.5, 60 and 130 volts to supply the transistors, valve heaters and valve anodes respectively.The operating conditions and the reliability of the entire repeater system are discussed in the paper.