HD Raio is a secondary digital signal added to AM and FM radio stations. With this technology, local radio broadcasters can provide listeners with more audio content through FM multicasting, higher quality sound and new data services, while remaining in their traditional places on the radio dial. HD Radio broadcasts are available today to more than 83% of Americans subscription-free. As with traditional AM, FM and TV broadcasting, HD Radio programming is free and supported either by commercial advertising or public broadcasting. Therefore, HD Radio is considered an attractive alternative to satellite radio, which charges a fee for its use.