SR wrote:
Yes, a friend told me that digital radio for the broadcast band am/fm
came out. And that WWOR (NYC) mentions it on their announcements.

Actually WOR; WWOR is the TV station formerly known as WOR-TV but no
longer related. WOR is one of the biggest proponents of digital AM
broadcasts.

Do you have to pay for reception?

You have to buy the radio, but there is no subscription fee. The radios
are still pretty expensive. That might (or might not) change someday.

Did they make the AM/FM bandwidth longer?

Wider, yes.

Digital AM occupies the two channels on each side of the one used for
the analog broadcasts. WOR is on 710KHz; their digital signal uses 690,
700, 720, and 730.

Digital FM uses the "guard bands" between stations. The signal doesn't
actually "spill out" of the station's existing channel, but on most
radios it will have the same effect as the station using the channel
either side of its analog channel. WNEW-FM's analog signal is on 102.7;
their digital signal will smother any stations on 102.5 and 102.9.

Are all stations moving on to it?

Probably not.

U.S. stations may choose to go digital at any time; they must notify the
FCC they've done so, but they don't need FCC permission in advance.

AM stations may not operate their digital transmitters at night.
(because WOR covers much of the eastern U.S. at night, their digital
signal on 700KHz would clobber WLW in Cincinnati; their other digital
sidebands would clobber other stations; and if WLW were to run digital
at night it would clobber WOR too.)

Clear Channel, the largest group owner of radio stations, has announced
a plan to convert 100 of their stations to digital each year. They own
something like 1,400 stations, so that's going to take awhile!

While you don't have to pay a subscription fee to *listen* to digital
radio, the stations must pay a technology licensing fee to *transmit*
it. I think between that fee and the cost of additional equipment, many
smaller stations will not bother with going digital.

Many observers don't think the digital radios will sell well enough to
make the service viable. We think digital AM/FM will go the way of AM
stereo.

Would we still be able to use our old analog radios?

At least for the time being, yes. Digital broadcasts are currently in
"hybrid mode", where the same station broadcasts both a digital signal,
and an analog signal compatible with existing radios.

The standard does allow for a digital-only mode which would not work
with existing radios. The theory is that someday, manufacturers will
stop selling analog radios. When all the analog radios have been
replaced, and everybody has only digital sets, the stations can switch
from hybrid to digital-only. The move would allow stations to offer
additional programs on the same frequency.

Given the number of people I know who routinely use 20, 30, and even
40-year-old radios, I don't think we'll see digital-only anytime soon!

And if new stations came on digital radio it in the future, would it be
heard on analog radio for those who do not have digital radio at home?

For the most part, the new digital system doesn't allow for new
stations. A digital station can only exist as adjunct to an analog
station. If a new analog station is not possible in a given location, a
new digital station is not possible. Since you mentioned WOR, I assume
you're in or near New York City; I can assure you there are no
frequencies available for new stations anywhere near there!

There is one qualification to that. The digital standard does allow a
single FM station to carry multiple programs on the same transmitter.
My understanding is that two programs are possible in hybrid mode;
presumably, more are possible in all-digital mode. WOR (being an AM
station) will never be able to carry additional programs, but WNEW-FM
could theoretically launch a new station on its digital signal. You
would *not* be able to receive this station on your analog radio.

I wonder if shortwave would be in digital in the future?

It already is, to some degree. The DRM (Digital Radio Mondiale) system
has been developed to allow digital broadcasts on shortwave and AM.
Unlike the "HD Radio" scheme, DRM cannot be broadcast on the same
frequency as the analog signal.

http://www.ibiquity.com/hdradio/ for more information on U.S. AM/FM
digital radio.
http://www.drm.org for more information on digital shortwave.

--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com