A wireless signal repeater that cuts off output transmission when the repeater is receiving less than a threshold level of input signal strength (e.g., too low or nonexistent). When operated in the reverse link of a cellular wireless system, the repeater advantageously reduces transmission of noise toward a cellular base station when the repeater is receiving no (or insufficient) signal from the a mobile station. Similarly, when operated in the forward link direction of a cellular wireless system, the repeater advantageously reduces transmission of noise toward a mobile station when the repeater is receiving no (or insufficient) signal from a base station.