Read the original FCC document on these links:
30 days after publication in the Federal Register, IBOC digital radio ("HD Radio") will cease to be something authorized through Special Temporary Authority and become a normal part of American radio. The biggest difference listeners (and especially DXers) will notice is that AM stations will be allowed to operate their HD signals at night.
The highlights, as the Commission puts them:
A few notes of my own:
Going back to the international considerations...
Canadian commenter Barry McLarnon quotes an article in the US-Canada agreement that states: "
“Classes of emission other than A3E, for instance to accommodate stereophonic systems, could also be used on condition that the energy level outside the necessary bandwidth does not exceed that normally expected in A3E....”
McLarnon argues that the IBOC digital carriers extend the station's bandwith to approximately 28KHz, far outside that necessary and normally expected from an A3E (regular analog AM) signal. He also notes that an identical clause exists in the US-Mexico agreement.
Editorial comment: Barry is 100% right.
Editorial comment: But since when does the U.S. government listen to any other country when there's money to be made?