On Thu, 01 Mar 2007 05:35:31 -0800, Radiola wrote:
What is IBOC?

"In Band On Channel", aka "HD Radio". A system for transmitting a digital
radio signal "on the same frequency" as the analog signal.

Actually, the digital signal is transmitted in the adjacent channels - for
AM, two channels each side of the analog; for FM, one channel each side.

For example, in WSCR's case:
- Analog: 665-675KHz
- Lower Digital: 655.3-665.1KHz
- Upper Digital: 674.9-684.7KHz

It's not currently authorized for regular nighttime use on AM stations,
because of severe interference to skywave reception. Here in the States
they're still working on finding a way to allow nighttime use. (possibly
including simply deciding skywave reception is obsolete and accepting the
interference) It's looking like the Canadians have ruled out nighttime AM
IBOC altogether.