Astra Digital Radio (ADR) was a system used bySES fordigital radio transmissions on the earlyAstra satellites, using the audio subcarrier frequencies of analogue television channels. It was introduced in 1995. As of February 2008, there were still 51 stations transmitting in this format. ADR ceased on 30 April 2012 when analogue broadcasts onAstra 19.2°E ended.
The format used one mono audio subcarrier, which was normally allocated to an additional audio track or radio station, or one channel of a stereo audio track/station. The carrier was digitally modulated and carried a 192 kbit/s, 48 kHz sampledMPEG-1 Layer II (MP2) encoded signal. 9.6 kbit/s was available for data.
Special receivers were required to listen to ADR stations, although some combined analogue/digital satellite boxes and later standard analogue boxes were equipped to decode it.
ADR was succeeded byDVB-S, with which it is incompatible, despite both being transmitted using MP2 and generally at the same bitrates. As a result, when the final analogue switch-off on the Astra 1 satellites occurred, ADR became obsolete.
The majority of the channels to have been broadcast using ADR were in theGerman language.[1] Because of this, the system can in a way be seen to have replaced the GermanDigitales Satellitenradio system, dating from the 1980s, which used an entire satellite transponder to carry 16NICAM[2] encoded radio stations, and which closed in 1999.
