A target radio can be located and tracked by an array of anchor radios. The anchor radios are calibrated when each anchor radio transmits an anchor message that is received by the other anchor radios. The distance between anchor radios is known because their positions are known. The received signal strengths are dependent on distance and an attenuation value. The calibration operation uses the received signal strengths and known anchor radio locations to determine the attenuation values of the anchor radios. After calibration, a target radio transmission can be received by the anchor radios. Each anchor radio estimates the distance to the target. The distance estimates and the anchor locations can then be used to determine the target radio's location.