A system of generating tunable orbital angular momentum (OAM) radio beams and a method of measuring the OAM states are proposed and experimentally investigated. The OAM beams, which are generated by a uniform circular array, can be dynamically configured by controlling the digital signals in the baseband. A 2-D near-field scanning platform is built to measure the OAM states of the system. The platform can provide multiple feed ports for the transmitting array. Iteration is used to calibrate the amplitude and phase of each feed port. The experimental results demonstrate the feasibility of the proposed methods on generating and measuring tunable OAM beams.