When the FCC Rules allowed AM stations to transmit IBOC signals at night, concerns were raised about the potential interference that would result to all analog stations in AM band. In the end, there hasn't been the doom and gloom destruction of AM radio from nighttime IBOC use, and Radio magazine research has found mixed experiences relating to actual received interference.
Within days after Sept. 14, the day AM stations were allowed to transmit IBOC at night, Citadel Broadcasting Director of Corporate Engineering Martin Stabbert issued a memo to Citadel's AM IBOC stations that transmitted a signal at night. The memo instructed stations to cease nighttime transmissions because of interference issues. We talked to Stabbert about the memo and the interference problem to help set the record straight.