A broadcast auxiliary service (BAS) is any radio frequency system used by a radio station or TV station, which is not part of its direct broadcast to listeners or viewers. These are essentially internal-use backhaul channels not intended for actual reception by the public, but part of the airchain required to get those signals back to the broadcast studio from the field. usually to be integrated into a live production.
Examples include:
- studio/transmitter link (STL)
- transmitter/studio link (TSL)
- remote pickup unit (RPU)
- electronic news gathering (ENG)
Several of these bands exist, but the most frequently used band is the 2 GHz microwave BAS band for point-to-point transmission from mobile newsgathering units to mountaintop receivers.
Seven 12-MHz wide channels exist in the band. In North America, DVB-T, precisely the same modulation technique as European Broadcast, is used, using a constellation of QPSK, 16QAM, or 64QAM, enabling sufficient digital bandwidths at 6 MHz deviation for transmission of an MPEG transport stream at 10 or more megabits per second, producing three "lower", "center", and "upper" overlapping 6 MHz channels within each 12 MHz channel.
