We had a very interesting meeting this month. John Holt, Chief Engineer of WAMU(FM) put together a PowerPoint presentation which demonstrated some of the work performed to get IBOC working on WAMU. He then showed us some of the experimental work which was done in the area of the secondary data stream. Normally, the IBOC hybrid signal is approximately a 96 kilobit stream (There is capacity for an expanded 150 kilobit stream - the totally digital stream will ultimately be 300 kilobits).

Using an experimental license for the occasion, John organized a test which split the available 96 kb stream into 64 kb for the main audio channel, and 32 kb for secondary audio. For completeness, they used some D.A.V.I.D. equipment from the Manassas based company, which is capable of routing data along with audio (and even video if desired) to handle the Program Associated Data. They broadcast the main program audio on the main channel, and provided some news and miscellaneous programming (primarily talk) on the secondary channel.

They spent time during the tests driving several hundred miles in a car equiped with one of the IBOC-ready radios available from Crutchfield. While the digital signal tended to go away (due to the "cliff effect" sooner than the fringe analog signal became completely unlistenable, the general feeling was that the coverage was fairly indicative of the signal coverage area they would normally expect for their core listeners. Also, there was some hope that with other radios or other antenna arrangements, reception of the digital signal may reach further.

The results of the test left everyone involved rather optimistic as to the viability of the digital signal as well as the ability to handle multiple streams, whether audio or data.

One side issue which has not seen much press to date is the need to handle the Program Associated Data. For those who stream audio (particularly music) on the internet, you are probably aware of the need to provide additional data to identify song title and artist information, and even other data such as artist and album pictures, etc. This will probably become a major studio upgrade issue which will include the audio routing equipment in future studio designs. This may become an issue sooner than some are willing to think about it because the credit information will likely become a requirement.