The initial purported purpose of IBOC was greater fidelity. As FM triumphed over AM so was HD.... Well that lasted about five minutes. When the consultants got ahold of the idea they realized what everyone else already knew, but knew was a bad idea. PAY RADIO.
Each HD station has the option of brodcasting one clear signal or multiple inferior signals. Currently they broadcast one analog signal and one HD signal. These hybrids are supposed to be phased out and radioland go all-digital but the FCC keeps pushing back the deadline.
The multicast idea starts innocently enough. The first HD multicaster was WFAE 90.7 Charlotte, NC. As usual Public Radio paved the way. They experimented with up to 11! channels one day last April. There were only a few models of HD tuners at that tie and I am uncertain if there were ANY that were multicast-capable. The initial talk is about splitting talk programming and music programming into seperate channels, or to have channels of all local traffic information. It all seems so idealist at the time, stations would provide programming because they could, because they wanted to, because their listeners would like it. NPR promises 24 more multicasting outlets by the end of this year. [It's rumored that Phillys local 90.1 WRTI intends to split Their Jazz and Classical programming into two seperate channels eventually. ]
Then came the consultants. At the time of this writing WRAL, WUSN and WJMK all have second channels of differnt music content. The second channel in this case becomes a testing ground for new music, an outlet for a dropped format etc... but the big talk is that the other channel could be subscription only. Let me say that again SUBSCRIPTION ONLY!
Oy Vey. So the model is that people will pay for local radio. So it's kind of like satellite radio except there are ads, and it you cant receive it 30 miles away... Normally I give technology the benefit of the doubt. People like new toys, more bells and whistles, more pomp and flash but this does not wow me. The idea of paying for local FM channels of low quality audio does not grab me. If any of you find it compelling please let me know why because right now I do not get it.