Yamaha B-2 said:
Vinyl Rules - We know that the horrible HD broadcast is 98kb, where redbook CD is 1,440kb. Even MP3 is better than HD radio, at 128kb. Not much of a comparison in info/fidelity there. We also know that the feed to and from the satellite is digital. Any idea what bit-rate it uses?
Have no argument with those who like satellite for its convenience. But for fidelity there is no replacement of high-quality FM on a good tuner with a decent antenna. As I am listening to at the moment.
Glenn,
For a peek at what NPR uses in their studios, click on:
http://www.npr.org/studios/studios.html It is interesting to note that many of their studios still have ISDN lines in place, and I believe I know why: The ISDN data rate, with a speed of only 112Kbps (the other 16Kbps is required for clocking and does not carry any signal) is a
guaranteed speed and will never vary in speed like a DSL line can vary - It is a direct delivery from the transmitter of the signal to the receiver of the signal and does not utilize indeterminate routing like the TCP/IP protocol used by the Internet and DSL. With indeterminate routing, you sometimes get indeterminate delivery (like when the Windows Media File you are viewing freezes for a second or two). This kind of delay is not acceptable to the broadcast world, so they keep their ISDN lines in place.
ISDN is more than adequate for voice transmissions and in the advertising world, it is quite common for the music that is used in TV and Radio commercials to be delivered to the production studio via an ISDN line. And ISDN lines are cheap compared to dedicated T-1 lines - In most places, the charge for an ISDN line is well under $100/month while a T-1 can cost as much as $2,000/month or more.
For some heavy technical reading on satellite broadcast stuff, click on:
http://tinyurl.com/y3eocz
To quote from this site, "16-QAM (quadrature amplitude modulation) digital satellite broadcast equipment and satellite communications (SATCOM) systems that double the spectral efficiency of currently operational satellite links is described. It is shown that with this field-proven system, data transmission at a rate of 90 Mb/s (two multiplexed DS-3 signals) is feasible in a transmission bandwidth of 30 MHz. Extensive operational satellite tests performed over the T-303 satellite of AT&T demonstrated a BER <10-10 and no errors for several days. The practical bandwidth efficiency of these SATCOM systems is 3 b/s/Hz, i.e. double the currently used 1.5 b/s/Hz QPSK (quadrature phase-shift keyed) systems. The doubling of the spectral efficiency is attained with advance modem (modulation-demodulation), adaptive equalization robust synchronization, high-power amplifier (HPA) linearization (predistortion), and low redundancy powerful forward-error-correction (FEC) subsystems.
The systems may make possible the conversion of currently operational analog FM links into bandwidth efficient digital systems. In one 30 MHz satellite transponder three to four digitized high quality TV signals could be broadcast, or two standard rate DS-3 signals time-division multiplexed with a DS-1 rate signal and additional auxiliary data streams" And this was published 17 years ago, in 1989.
And for a look at a commercial audio CODEC used by some FM stations, click on:
http://tinyurl.com/ympzas It is interesting that the stereo data stream is quoted as being 768Kbps. This does not exactly answer your question, but a radio station engineer would have to provide an exact answer. I can only assume that an FM station broadcasting a good digital satellite feed would be using something similar to this piece of equipment and running it at a high data rate.