Digital stereo sound, NICAM-728, Methods for establishing NICAM quality of a TV transmission

In the NICAM-728 system two audio channels are sampled at 32 kHz and digitally coded with a resolution of 14 bits per sample. For transmission the samples are reduced by compression to 10 bits resolution and with a scale factor word carrying the compression ratio to the receiver is added. Transmission takes place by means of a differential quadrature phase shift principle, where a pair of bits is transmitted by shifting the phase `n×90°´ (n=0,1,2,3) of a subcarrier placed above the traditional mono sound carrier. The author discusses the aspects of adapting TV transmitters for NICAM-728 and highlights the difficulties expected and describes proper measuring equipment suitable for monitoring NICAM-728 transmission quality