There is provided a channel card for extending the coverage area of a base station, which controls GPS reference signals provided to base station modems to extend the coverage area by up to four times a general base station coverage area. The channel card includes: a controller for generating control signals for extending the coverage area of the base station; a system clock distributor for dividing a GPS reference signal applied from a GPS clock receiver to generate a plurality of system clocks; a coverage area extending clock generator for converting the GPS reference signal supplied from the GPS clock receiver into a plurality of signals under the control of the controller, to generate clocks for extending the coverage area; a coverage area extending clock controller for selectively providing the plurality of coverage area extending clocks generated by the coverage area extending clock generator to first to fourth base station modems under the control of the controller; and the first to fourth base station modems which operate according to the coverage area controlling clocks provided by the extension clock controller and the system clocks generated by the system clock distributor, to handle calls established in a first area having the minimum coverage area to a fourth area having the maximum coverage area.