You will never need to spend hours looking for your dog again. Tracker Radio offers the world's smallest, lightest and most portable RF tracking receivers. Tracker’s receivers are among the most technologically advanced dog tracking tracking collars on the market, offering reliability, flexibility and portability. The four antenna elements on the receiver fold down to make the receiver system no larger than the size of a flashlight for carrying in the field and storage.  How Dog Tracking Collars Work. Tracker Dog Tracking Systems are one of the few tracking collars with GPS, RF and hybrid configurations.