Editing Subcarrier (section)

==Datacasting==
[[File:OFDMA subcarriers.png|500px|thumb|Subcarries in the [[OFDMA]] scheme]]
The [[Radio Data System|RDS]]/[[RBDS]] subcarrier (57&nbsp;kHz) allows FM radios to display what station they are on, pick another frequency on the same network or with the same format, scroll brief messages like station slogans, news, weather, or traffic—even activate pagers or remote billboards.  It can also broadcast [[Emergency Alert System|EAS]] messages, and has a station "[[radio format|format]]" name ALERT to automatically trigger radios to tune in for emergency info, even if a [[CD]] is playing.  While it never really caught on in [[North America]], [[Europe]]an stations frequently rely on this system.<ref>The radio station [[Heart West Midlands|Heart FM]] used this service to cause people's radio sets to switch over to adverts for commercial vehicles during the morning and evening rush hours</ref> An upgraded version is built into [[digital radio]].

[[xRDS]] is a system with which broadcasters can multiply the speed of data transmission in the FM channel by using further normal RDS subcarriers, shifted into the higher frequencies of the FM multiplex. The extra RDS subcarriers are placed in the upper empty part of the multiplex spectrum and carry the extra data payload. xRDS has no fixed frequencies for the additional 57 kHz carriers.

Until 2012, [[MSN Direct]] used subcarriers to transmit traffic, gas prices, movie times, [[weather]] and other information to [[GPS]] navigation devices, [[wristwatch]]es, and other devices. Many of the subcarriers were from stations owned by [[Clear Channel Communications|Clear Channel]]. The technology was known as [[DirectBand]].

[[FMeXtra]] on FM uses dozens of small [[COFDM]] subcarriers to transmit digital radio  in a fully [[in-band on-channel]] manner.  Removing other analog subcarriers (such as stereo) increases either the audio quality or channels available, the latter making it possible to send non-audio [[metadata]] along with it, such as album covers, song lyrics, artist info, concert data, and more.