I found this further info. What do you think they are talking about when they say "specific channel authorisations"?
Echostar III transmits all transponders used by Dish and Sky Angel.
Transponders 2, 4, 5 - 8, 10, 12 - 14, 16, 18, 20, 22 are being used by Dish.
Transponders 26 - 31 are being leased by Dish from Sky Angel
Transponders 25 and 32 are being used by Sky Angel.
Failures. It can now operate 20 transponders but due to design and licensing limitations is using only 16 of 19 FCC authorized frequencies.
Transponders: During January 2004, a TWTA pair on EchoStar III failed, resulting in a loss of service on one of EchoStar's licensed transponders. Including the seven TWTA pairs that malfunctioned in prior years, these anomalies have resulted in the failure of a total of 16 TWTAs on the satellite to date. While originally designed to operate a maximum of 32 transponders at any given time, the satellite was equipped with a total of 44 TWTAs to provide redundancy. EchoStar III can now operate a maximum of 28 transponders. Because of redundancy switching limitations and the specific channel authorisations, currently it can only operate on 17 of the 19 frequencies at 61.5 degrees West authorised by the U.S. Federal Communications Commission.