A system and method effectively combines communications of the base stations of multiple wireless systems on the same antenna structure. In one implementation, a wireless system combiner serves as an interface between base stations of first and second wireless systems ("first base station" and "second base station") and a shared antenna to substantially eliminate spurious noise from the first base station at frequencies allocated to the second base station and prevent transmit power from the first base station from feeding into the reception circuitry of the second base station in a shared antenna configuration. The combiner includes a first combiner filter between a duplexer of the first base station and a common connection point and a second combiner filter between a duplexer of the second base station and the common connection point. The first combiner filter filters out spurious noise generated by first base station transmitter at frequencies outside the frequency band allocated to the first base station, for example using a high Q value band-pass or band-reject filter. The second combiner filters out signal power at frequencies outside the second base station receive band to prevent transmit signal power of the first base station from feeding into the second base station's receiver circuitry, thereby preventing intermodulation.