The SCA (Subsidiary Communications Authority) was a sub-carrier quite a distance from the main carrier and was not detected by the standard FM receiver. The audio quality was very low. I think the maximum was only 8000 Hz or something relatively modest but worked well for speech.
The IBOC (In Band-On Channel) system is used for the HD-AM transmissions which simulcast analog and digital. There are problems. On Oct, some of the ABC Radio affiliates were shutting off their IBOC transmissions at night due to adjacent channel interference to other stations and they felt the performance was as good as they had initially thought. I don't think many consumers are buying the receivers so you also have a chicken and egg situation. IBOC is also used on FM (88 to 108 MHz), and I would expect it to work better than on the relatively narrow 10 kHz AM BCB. If you have been following the press on DRM, it has been somewhat unfavorable since the quality improvement is not always that good either due to multipath issues. It seems hard to believe, but there was some claims that Sangean will discontinue DRM for their SW receiver. I could not confirm this out from their web site, but I also could not find DRM SW receivers either. The DAB transmissions from satellite is quite good and gives you over 100 channels, but you do have to pay a subscription fee. 73, Rick, KV9U John Becker, WØJAB wrote: > This has been going on for over 25 years that I know of. > But I don't think it was digital. AM and FM radio had a > service for the blind that was a sub carrier. Sounds very > close to it. > > At 06:29 PM 11/12/2007, you wrote: > >> In the U.S. the FCC has approved a system called IBOC (In-Band On Channel) >> to add digitial audio to existing AM and FM stations. In broadcast radio, >> there isn't the luxury of unused channels that allow every station to have >> one analog and one digital transmitter. I haven't seen any terrestrial >> digital radio receivers in stores yet. >> > > > > Announce your digital presence via our Interactive Sked Page at > http://www.obriensweb.com/drsked/drsked.php > > Yahoo! Groups Links > > > > > > >
