Originally the FCC required stations to broadcast the same material on analog and digital channels. Because the range of the digital transmissions were predicted to not cover the entire service area of a station's analog service, it was mandated that receivers soft switch back to the analog service when the digital service became erratic. That is why it is necessary to time sync the two streams so, as the soft transition blends from digital to analog, the transition would be transparent to the listener.
The article points out that if there is as little as a fraction of a millisecond of error in the sync process, notches in the recovered audio spectrum would appear during the blending of the two signals. If that error was 1 millisecond, article author observed notches at 500 Hz, 1500 Hz, etc. This is due to the phase of those frequencies being 180 degrees out of phase with a 1 millisecond delay. I have been away from developments in this area recently. You obviously have an advantage on me in that you have an HD receiver. WHYY-FM and WETA-FM are both public radio stations. Maybe FCC has given them authority to run separate programs in order to raise more public funding and offload the need for government subsidy. I wonder if any commercial stations have separate programs? --- [EMAIL PROTECTED] wrote: > Huh? The FCC requires identical programming on digital and analog? > Here > in Philadelphia, I listen to classical music on the HD radio from > WHYY-HD, > while listening to talk on WHYY-FM. In Washington, DC, WAMU-FM is > regular NPR > news/talk/features, while one of their HD channels is strictly > bluegrass > music. Am I misunderstanding what you're saying, Joe? > No. Sounds like the predicted transition is already happening at least for public radio stations. It would be enlightening to know if you hear anything other than simulcasting on the primary digital channel and the analog channel on any commercial stations. Joe __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com _______________________________________________ Swprograms mailing list [email protected] http://montreal.kotalampi.com/mailman/listinfo/swprograms To unsubscribe: Send an E-mail to [EMAIL PROTECTED], or visit the URL shown above.
