It is difficult for the operators to maintain good signal coverage for the tourism regions, mining districts or villages in the mountain area, due to the obstacles and surroundings. Building base stations to provide coverage isn’t the best solution since the population is low in the mountain area. In this kind of environment, the Frequency Shift Repeater is good coverage choice, it can efficiently provide coverage to the mountain area with a reasonable cost. They comprise of donor unit and remote unit, link antennas, coverage antenna, coupler, and RF coaxial cables and jumpers. The donor unit captures the base stations signal via direct coupler close to base stations, then converts it from the working frequency to the link frequency, and transmits the amplified signal to the remote unit that will reconvert the signal to the working frequency and provide the signal to the areas where network coverage is inadequate. And the mobile signal is also amplified and retransmitted to the base station via the opposite direction. It is suitable for both cellular network and critical communication network such as TETRA/IDEN/PMR.