a time division multiple access radio system conveying a quadrature phase shift keying modulated data signal is disclosed . in order to overcome multipath distortion and phase variation introduced by the radio channel , a synchronizing poriton of a tdma timeslot is transmitted in only one vector of the qpsk modulation . the system utilizes the one vector synchronizing portion to develop a channel profile estimate which is applied to the received message portion of the qpsk data signal to compensate for the multipath distortion and phase variation during one tdma timeslot .