I found this very interesting regarding HD radio.
On Thursday the 22nd of March, 2007 the Federal Communications Commission
approved all facets of digital broadcasting in the USA. In particular, AM
stations will soon be authorized to begin 24/7 use of their first adjacent
frequencies for digital sidebands.
What this does is open the door to significant interference to all AM
stations. A 50kw clear channel station can run a digital transmitter at
far
more power than would be authorized for any conventional station in that
location on those two adjacent frequencies. It will be interesting from a
rather perverse sense to see what happens at night..
I have had two HD Radios, and found that the digital signals are very
fragile, and cover about half the radius (1/4 the area) of a good analog
signal. Electrical noise from many sources like car ignition, light
dimmers
and bad wiring can easily disrupt things.
The programming is the real draw to a station, and HD Radio on AM will
provide no change at all. A talk show in digital "high quality" is still a
talk show. In the 35+ years I've been a broadcast engineer, I have seen a
small handful of complaints about audio quality. These have always been
when
there is some correctable flaw, like a hum. Quality is not the issue and
never has been.
I saw an interesting comment. Name and location deleted to protect the
writer:
"The latest e mail from xxxxxx in xxxxxx said that the reason the big boys
in the big markets are so pro IBOC is because they like the hash as it
wipes
out distant signals getting into their market. There is no way to stop
skip,
but if the IBOC hash wipes the signal out, then the locals will have to
listen to their local station. Kind of like legal jamming. Considering
that,
then even if the public does not buy the radios, keeping the IBOC signal
might be worth their while."
Jamming is illegal in many ways. If some entity has manipulated this
process
to allow it, then appropriate action should be taken to shut it off.
One possible result is many smaller non-IBOC stations refusing to drop
power
at night in an attempt to keep their current coverage area. Or, installing
bigger transmitters to outright cheat to keep the coverage radius they had
pre-IBOC. That would make a very interesting case, should it ever go to
court. Two wrongs don't make a right, but when one of the wrongs is
legalized, all bets are off.
Shouldn't the digital sideband powers be calculated by the same rules as
used for analog signals? Just plopping in a new signal on a frequency
without any regard for it's interfering effects is a recipe for chaos. No
new station could be allocated today without a full allocation study. Why
are these new digital allocations exempt? In effect, they are really two
new
stations in themselves.
What if there are unequal powers allocated for the upper and lower
sidebands? For technical reasons, IBOC requires the two sidebands to be of
equal strength to minimize interference to the analog signal. Didn't they
see all this in the formulation stage? Or did they simply decide to ignore
the obvious and forge ahead, oblivious?
There are some stations that have directional arrays that may never be
able
to be compliant with the specs for IBOC transmission. As a result, they
will
not be able to run it. Is it fair that some can and some cannot be
digital?
If digital-only operations are mandated, will these stations be forced to
go
dark? Is that fair to their communities? It would seem that many small
town
stations cannot afford the license nor the technical upgrades. Again, if
digital is mandated, do these small towns simply lose their station, even
if
it is the only one? That seems grossly unfair.
Customers are staying away from these radios. Market penetration is very
much below the radar. They hope to sell two million HD Radios by the year
2010. That's about how many iPods sell in a month.
Many years ago WLW had a project for HiFi radio. They made sure their
transmitting plant was flat out to +/- 20KHz. There were receivers in that
time that were up to that task as well. I would dearly love to hear that
setup today, and compare it to the HD signal.
Instead of inventing this intrusive technology, they could have spent
their
efforts on DSP-based receivers to minimize impulse noise and other
interference. A good DSP decoder can null out a coherent tone such as a
10KHz heterodyne without a negative effect on the audio. It could also
compare the upper and lower sidebands to determine what would give the
better sound. It could narrow the bandwidth to the most efficient point
for
best reception. And, the DSP decoder could look over a wide swath of
spectrum to detect wideband noise and remove it. The technology is there,
but they chose to ignore it.
Heck, if they could get such a good analog signal decades ago, what
happened? What if a station today decided to use the mask designed for
IBOC
and implement a wideband analog signal? Would it be legal? How would that
sound compared to the HD version,. assuming a good wideband receiver could
be found? What if it even sounds better than HD Radio?
One of the significant problems of AM these days is the ****elding effects
of
newer steel and concrete building construction. AM simply doesn't
penetrate.
Why did they think that overlaying a digital signal on the same band would
penetrate these buildings any better?
A better overall plan would have been to embrace streaming technology.
WiFi
access is exploding, and WiFi-enabled iPods will soon be introduced. An
iPod
can do many things and at less cost than most single-purpose HD Radios.
Streaming audio can have much better quality than even the best HD signal.
Instead of HD1 and HD2, it is possible to have unlimited streams. The
formats that can be streamed by a station are limited only by their
resources and imagination, not some technical limit of their transmission
medium. Reception of a stream is possible anywhere there's an internet
connection, not limited to the coverage radius of a single transmitter. It
literally is global. Power costs to run a stream are insignificant
compared
to a transmitter. No large towers, or arrays of towers are needed.
Streaming
is far more "green" than IBOC, if you care to look from that perspective.
In
terms of quality, variety and environment, HD Radio is obsolete right out
of
the box.
From a business angle, having the FCC mandate a proprietary system is
unprecedented. All previous systems for anything were all open source. The
technology to create a piece of equipment was there, every parameter. With
HD Radio, none of these parameters are public, at least not enough that
some
clever engineer could roll their own. This is very unfair, and smacks of a
monopoly. The whole HD Radio specifications should have been in the public
domain. Were someone to reverse engineer this method, no doubt they would
be
hauled before a judge and significantly fined. All because some company
has
convinced the federal government that it has the only way to do the job.
The
parallel would be if the government decided that to drive on the
interstate
you had to buy a new Buick.
Recently it was announced that there may be pay-to-listen encrypted HD
broadcasts. Could this be why they want the system proprietary? So nobody
can legally write a decoder to bypass their pay scheme?
In conclusion, I'll relate a conversation I had with someone who has an
extensive non-technical radio background. A local Clear Channel GM gave
this
person an HD Radio. It was tried, and shut off. Decoding the signal was
very
problematic even within the city grade contour of several stations. This
person related to me that HD Radio was a bad joke and a complete waste of
time. This was said without me even bringing up the subject. It seems to
be
a common "joe average" result when a non-radio person tries HD Radio. Too
much effort to get a signal. They want to turn it on and get flawless
audio,
just like their iPod. It doesn't happen, so they simply return the radio
for
a refund saying it "doesn't work".
Well, I have had a fair bit of feedback on this article. Here are some
samples.
* I agree 100% on this. The noise is horrible.
Reply: Unless everything is exactly right, that noise also intrudes onto
the
analog audio. Background hiss.
* Are you some sort of Luddite? Do you want radio to die? I cannot believe
you would attack radio when it is only tryeing (sic) to survive.
Reply: No, not a Luddite, at least not in most things. My objection is
entirely from them trying to force signals onto an inappropriate band. The
AM band is completely wrong for digital signals when overlaid onto the
existing analog content. There is insufficient station assigned bandwidth
to
do it right. There is way too much noise from too many sources. The night
propagation absolutely insures that interference from other stations will
be
a problem. This band does not get into modern concrete and steel
buildings.
Many of the existing facilities may never be able to be engineered for
sufficient bandwidth for the digital carriers. Finally, going all digital
will make a half billion (with a B) radios useless. This should have been
in
another frequency band. Period.
* Have you ever listened to HD Radio? Don't you think it is worth the
cost?
Reply: Yes, I have indeed listened extensively. I have bought two
different
radios out of my own pocket to check it out. The primary content on AM is
voice. The current analog receivers do sound muddy and sometimes
distorted.
However, I do clearly remember the great sounding radios such as Zenith
and
others built. I adapted a Belar RF amplifier once with a great linear
detector on the output. It sounded amazing! As do most of the modulation
monitors used. I would put the analog audio from one of those against the
AM
HD audio any day. Dymek-McKay also built some excellent HiFi type radios.
Given the relatively low digital audio rate of AM HD Radio, I think these
analog examples might even sound better. So, what's the advantage? Being
able to see Artist/Title info? Hardly worth it. In fact, I bet I could
figure a frequency ****ft keying method for existing analog stations to add
the Artist/Title and associated info.
* You will never work for my company.
Reply: Probably not. If your company cannot accept a critical view, then I
would not want to work there anyhow. I have stated on several occasions
that
my personal views in no way affect my work performance. If someone wanted
to
pay me to put AM HD Radio on, I would do my best to make it happen. So far
only one of my clients has any interest in HD. And the timeline for that
is
at least a year away.
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