AM Stations May Be Affected by USA HD Radio--CAB

http://www.broadcastermagazine.com/issues/ISArticle.asp?id=73219&issue=09042007

As of September 14, US AM radio broadcasters that have implemented HD Radio will be allowed to transmit their digital signals at night as well as in the daytime.

Canadian AM stations operating on frequencies that are first and second-adjacent to powerful US stations may experience increased levels of skywave interference after dark as a result of this recent FCC decision.