"In-band on-channel (IBOC) is a method of transmitting digital radio and analog radio broadcast signals simultaneously on the same frequency.
By utilizing additional digital subcarriers or sidebands, (?) digital information is "piggybacked" on a normal AM or FM analog signal, thus avoiding any complicated extra frequency allocation issues. However, by putting extra RF energy beyond the edge of the station's normally-defined channel, interference with adjacent channel stations is increased when using digital sidebands....." from wikipedia These fellows here in the USA are doing it wrong! "... by putting extra RF energy beyond the edge of the station's normally-defined channel, interference with adjacent channel stations is increased when using digital sidebands..." Thats a no no under accepted practice terms. Widebanded ... If the extra energy is in the region of the channel edge or beyond as in extended sidebands then this method is not at all ideal on AM. For FM use however it is ok. This method is as I understand made for patented uses. So it is the selling of a patent. On the other hand the use of DRM as a digital mode confines all of the signal into a channel and is more efficient and does not lend to adjacent channel bleed over. My USA folk are not wanting to follow with using DRM which is the only possible currently successful concept for digital mode operation of AM without messing up the band. So IBOC is just someone trying to foster a patented HD system off on the public. And monopolizing the HD market. That method of use (IBOC) would be laughed at I think by people in the field of software defined radio. It would make the Mediumwave Band a mess. And it is in use here. However they have found out that they have to take it off the airwaves at night. Maybe it will die out. DRM sounds like the better choice for HD uses.
