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?
thanks,
Mario.


"umarc" ha scritto nel messaggio
...
I finally got to hear HD Radio (a.k.a. IBOC) on several Boston FM's
Saturday night (but not any AM's since it was night). My observations:

1. HD Radio does not sound appreciably better than FM.

2. On some of the stations there was a "gritty" quality to the sound
reminiscent of an MP3 Internet stream. To be fair, this could have
been the result of cascading HD Radio with an STL or digital audio
storage system employing something like MPEG or apt-X compression,
and not something inherent in HD Radio itself.

3. HD Radio does not appear to extend a station's coverage. On the
fringe of one station's coverage, where it could be heard in analog
FM imperfectly, the HD Radio was generally not audible at all. We
estimated that the effective range of the HD Radio signal is 90 to
95 percent of that of the analog FM.

4. The Kenwood receiver seems to mute in digital mode if there is
another signal on an adjacent channel.

5. It also mutes in the presence of nearby FM transmitter sites.

6. In analog mode, the digital sidebands of a station running HD
Radio can be heard as white noise. It is not yet possible to
guess how much interference they may cause because only a few
stations are running HD Radio yet.

7. The scrolling text display some stations were running may be a
considerable distraction to drivers.

After hearing some glowing reviews, I was prepared to hear something
approaching the sound of a CD and to want to push to put it on
our stations. Instead, my friends and I were asking ourselves why
anyone would want to pay $75,000 for it.

However, I am still reserving judgment. One night of listening on
one radio isn't enough; I want to hear it on several different
radios on a wider variety of stations, under different reception
scenarios. I'm particularly interested in the effect of adjacent-channel
interference.


umar

"Mario dei Pintarei" writes:

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?

We don't have DAB because the National Association of Broadcasters
lobbied against it several years ago when they realized it would give
all stations in a market essentially the same coverage and possibly
allow new competitors into the game.

They do have DAB in Canada, but we have IBOC ("in-band, on-channel"),
or "HD Radio" as it has been recently rebranded. HD Radio allows a
station on the AM or FM bands to transmit a digital signal along with
the conventional analog signal. The catch is that the maximum bit
rate permitted by HD Radio is 96 kbps on the FM band and about 36 kbps
on AM. By comparison, DAB allows up to 256 kbps.


umar

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