So, is DAB just theoretical fiction? No. Digital compression has saved the day. Digital compression technology has made it possible to compress digital signals to allow transmission within a much smaller bandwidth. (You can read all about Digital Compression in my articles on MP3.) Digital compressions has made it possible to reduce the number of bits in a stereo signal from 1.5 million down to less than a quarter of a million per second, without any noticeable difference in perceived sound quality. This reduction in digital radio signal bits reduces the amount of bandwidth required by digital radio as a whole. And thus we have Digital Radio!
Here another problem creeps in. Which frequency and bandwidth to use in transmission of Digital Radio? The AM and FM bands are not practical for digital radio since these bands already crowded and also suffer from interference problems. And satellite transmission would be impossible unless you want a huge satellite-receiving dish perched on top of your house or car. As a solution Canadian research proposes the use of the L-Band. Researchers have proved that L-Band digital radio transmissions have none of the problems associated with AM and FM. In fact, L-band digital radio are compatible with both land based and satellite based transmission systems and can be designed to provide interference-free reception in moving cars and on personal portable radios. But it isn't as easy as it sounds. Unfortunately in the U.S.A. the L-band is consumed by licensed and aeronautical systems and is not available even for testing, let alone the establishment of a permanent set of frequencies within it for DAB. The proposed solution is to put DAB on the S-band. If this is done then it would mean that US DAB would be out of step with the rest of the world, presenting huge problems to the producers of broadcasting and receiving equipment.
