A communication system includes a hybrid fibre/coax distribution network. A head end generates a master clock signal and derives a head end RF clock signal locked in frequency to the master clock signal. A head end symbol clock signal is derived, locked in frequency to the master clock signal, and multiple strings of downstream digital data are converted to sequences of symbols at times determined by the symbol clock signal. The symbols are modulated onto multiple orthogonal carriers having frequencies determined by the RF clock signal. The modulated orthogonal downstream carriers are transmitted over the distribution network to remote locations.