A novel synchronization technique is described. In this method symbol timing is derived from the received data. This method of synchronization is highly suited to a communication path in which there are a number of modes of propagation, e.g. the HF channel. The operation of M-ary FSK (frequency shift keying) and PSK (phase shift keying) modems using the trellis coded modulation technique in conjunction with intrinsic synchronization is presented. HF trial test results are presented