An apparatus for indicating a direction of a radio transmission is described. The apparatus includes at least one vector detection device including two or more antennas and an attenuating material between at least one of the antennas and a source of a radio transmission. The attenuating material is arranged to vary an amount of attenuation with an angle of the source with respect to at least one of the antennas. The apparatus is configured to generate a signal indicating a direction of the radio transmission by comparing received signal strengths from the two or more antennas.