Thanks for the interesting information.
Just a minor point for clarification purposes. HD Radio (as trademarked by iBiquity) is a specific implementation of an in-band, on-channel (IBOC) digital radio technology. It has been approved by the FCC for use in digital AM and FM applications, but is not very widely used outside of North America.
iBiquity's official stance is that the "HD" does not stand for anything. Most HD Radio broadcasts carry less than "CD quality" audio, so they can hardly be classified as "high definition" or "high fidelity". The audio quality in most cases are about the same as what you'd expect out of a traditional analog FM broadcast.
At one point, the "HD" was said to mean "hybrid digital" since this signal was designed to co-exist with an active analog broadcast (analog and digital signals simultaneously carried on a single channel). However, the company no longer supports this definition.
I'm sure they are happy with the fact that many consumers will mistakenly take HD to mean "high definition" even though the audio quality does not really support such a classification. But I digress...
In other parts of the world, different digital radio broadcast standards are used. These include standards like
- S-DMB and T-DMB
All of these standards are bringing digital radio to more people all around the world. Together, with HD Radio, the hope is that there will be a growing awareness and demand for digital radio products and services.