As Mitchell explains: “The NICAM equipment … in the basement of Broadcasting House was originally installed in the autumn of 1983. The circuit boards that made up the NICAM equipment were failing due to their age and the supply of spare circuit boards was running out. In addition, the faulty circuit boards were becoming difficult to repair because some of the components they use have become obsolete and can no longer be bought. So we looked to make a replacement.”
He continues: “…the new coder … replaces the 3 data combiners (which combine the RDS data with the transmitter control information), the 6-channel audio coder, the CRC inserter, the CRC checker, the 6-channel audio decoder and the 3 data splitters (which separate the RDS data and transmitter control information). It also includes the NICAM test waveform generator.”
Here’s a photo of the inside of the new NICAM codec box with the ZedBoard located in the center of the image:
Zynq-based BBC NICAM Audio Codec with ZedBoard in the center of the image
How well did the switchover work? It’s all in the title of Mitchell’s article. Nobody noticed. That’s the hallmark of a 100% successful replacement effort.