HD Radio right now is broadcast over existing radio channels, both AM and FM. It is not truly on-channel, as the IBOC (in band on channel) acronym would suggest, but on the two adjacent channels. This both causes interference to and receives interference from neighboring stations, especially in crowded metropolitan areas. The full-digital is designed to have the signal only on the assigned channel, but it will be roughly a decade before that could happen. Receiver penetration is simply too low, which would cut off the vast majority of listeners from stations if done too soon. That would be suicide.
So, where will we be in a decade? Given the extremely rapid progress of things like streaming audio and iPod-type devices, it's safe to assume that personal multi-function devices will be the norm. These will replace cell phones, iPods and PDAs, plus other functions like GPS and navigational accessories. WiFi will be universal in most metropolitan and suburban areas, corresponding to cell coverage. You'd have to get pretty far into the boondocks to be out of range. Potential satellite augmentation may even fill those gaps. Global coverage will be expected.
Such a versatile pocket accessory will no doubt include audio capability, both live and stored. Bandwidth will be more than enough for video, and certainly 5.1 or 7.1 surround audio at flawless fidelity. What consumers want is the electronic equivalent of the Swiss Army Knife, and they want it for lunch money.
Consumers will have the choice of spending maybe $100 on a single-function, very limited program source HD Radio with a small coverage footprint. Or, probably less than that on a pocket device which gives them essentially unlimited program choices, and about any other function from email to car navigation with nearly global coverage. Sounds like a no-brainer to me..
Here are some points..
1. HD Radio has very limited geographic coverage. As of this writing (May 2007) there is no night AM HD Radio.
2. Receivers for HD Radio are not selling, nor are manufacturers enthused about it. GM has adopted a wait and see attitude on including them in new cars.
3. Program choices are limited to one on AM, and two or three on FM. Multiple choices come at a cost of lessened fidelity due to bandwidth sharing.
4. Streaming audio has none of these limits. Program channels are limited only by the resources and imagination of the content provider. Coverage soon will be similar to that of cell phones.
5. WiFi-type iPods will sell because they do everything, not just play radio. Quantity sales will keep prices rock bottom.
As I've said, I have advised my clients to look past HD Radio and spend time and effort on streaming audio. I have also encouraged things like video and 5.1 audio archiving. The future is there, not on terrestrial bandaids. Technology becomes obsolete. Buggy whips are still made, but are hardly mainstream. Vinyl records, Betamax and 8-track tapes all had their day, but are past. They still have a small and dedicated fan base, but hardly enough to support a major industry. HD Radio and broadcasting as it is structured today will join them before too long. Content is King, the delivery is secondary - as long as it's convenient to the masses. That delivery will be via a practical and fun device that does many things, and does them all well. It will not be a single function overpriced radio.