Mario dei Pintarei wrote:
Hi,
How does HD radio work? I'm an equipment designer (remote control
equipment) from Italy, we don't have it here. Never even heard about it! Is
it Digital? Modulation CODFM? what is the bandwith? Here in Italy we have
DAB... do you have that in the US?

I guess you could say "HD Radio" is the DAB system in the United States.
It is (very!) technically incompatible with the Eureka DAB system used
in Europe. http://www.ibiquity.com .

HD Radio is also known as "IBOC" - "In Band, On Channel". It places
digital carriers in the outer edges of the existing analog signal. (and
for MW IBOC, in the adjacent channels) It offers a "hybrid mode" in
which DAB and analog can be broadcast on the same frequency at the same
time.

All U.S. stations are currently allowed to begin DAB broadcasts at any
time, upon notifying the government. MW stations are only allowed to
broadcast DAB during the day, though nighttime authorization has been
requested. Very few stations are actually using DAB at this time - my
guess would be roughly 50 (most of them VHF/FM) throughout the country.

It is (IMHO) specifically designed to maintain the relative coverage
areas of different stations. (unlike, for example, the Eureka DAB in
Canada where all Montreal DAB stations have equal coverage, regardless
of the coverage of their associated analog stations)
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

Doug Smith W9WI had written:

| All U.S. stations are currently allowed to begin DAB broadcasts at any
| time, upon notifying the government. MW stations are only allowed to
| broadcast DAB during the day, though nighttime authorization has been
| requested. Very few stations are actually using DAB at this time - my
| guess would be roughly 50 (most of them VHF/FM) throughout the country.

In the San Francisco area, there are five, all FM:
KZBR, KOIT-FM, KDFC, KFOG, KSAN.

None observed on AM so far, but given that Susquehanna owns the latter
two stations listed above as well as KNBR(AM) and KTCT(AM), I think
it might be merely a matter of time.

Bonneville, the other owner represented above, only owns one San
Francisco AM, KOIT, which simulcasts the FM 100%. One suspects that
Bonneville is unlikely to invest too much into that signal (which is ND
fulltime).

On FM, the IBOC sideband noise that is generated is noticeable on a
receiver of any but the worst quality. The KSAN IBOC signal (licensed
frequency of 107.7 MHz) is blamed by some for blocking South Bay reception
of Monterey Bay-area station KPIG (107.5 MHz).

--
"You're about to see a great sunset if you're in the right place."
-- KCBS morning traffic anchor, 6.58 am, February 9, 2004