Thoughts on DRM and HD Radio
We have entered the era of digital radio broadcasting, and engineers
will face many daunting but interesting challenges as HD Radio is
rolled out, especially on the medium-wave side. There are several
obvious issues, which include antenna bandwidth, nighttime operation
and the somewhat less obvious issue of protecting the digital signals
that are not systematically protected on the adjacent channels.
The timing is right to consider if there are other methods that
would give broadcasters additional tools for their conversion to
AM or medium-wave broadcasting has always been an extremely
important and powerful broadcast medium. It is a universal technology
available worldwide. Surely that point was a big factor for USA Digital
Radio when, on Jan. 24, 2000, the company agreed to work with the
Digital Radio Mondiale (DRM) consortium to develop a universal, world
standard for digital radio. Because no production-line receivers for
digital radio exist at this time, it is difficult to determine the true
compatibility of these two systems. Both are part of the ITU digital
broadcast specification BS 1514-1. HD Radio is referred to as
“double sideband IBOC.” Technically, the two systems
utilize OFDM modulation techniques with some form of QUAM modulation.
Until recently, both used AAC audio coding; Ibiquity now uses the PAC
algorithm. Other than the requirement to license two audio coding
algorithms, building a universal receiver for use anywhere in the world
should not be an issue.
The point is that there is no good reason why American broadcasters
should not have the ability to use either of the two digital methods
described in the single ITU 1514-1 specification. This would not be a
“marketplace decision” as it was with AM stereo, primarily
because there has already been effort put into making the two systems
part of one standard. DRM is has already been authorized by the FCC for
use (at least experimental) on the short-wave bands.
DRM is the International standard for digital radio below 30MHz
according IEC specification 62272-1. It is non-proprietary and
license-free. DRM offers scalable bandwidth, varying degrees of
ruggedness vs. quality and is optimized to deal with sky-wave
transmission. DRM also permits multiple programs (up to four) as
opposed to HD Radio, which offers a single channel. DRM can support
synchronous transmission so that a network of low-power boosters could
replace large transmitter sites. There are DRM synchronous systems now
Ignoring the additional features of DRM, why muddy the waters now?
Some good reasons are that a DRM approach could easily solve the night
operation issue and be more compatible to narrow-band antennas. DRM can
operate in a bandwidth as small as 4.5kHz or be expanded to carry more
data and programs to a full 20kHz wide channel. This possibility plus
the ability to choose one of two different levels of QUAM and from one
of three audio compression schemes make it possible to optimize the
signal from a very FM-like stereo signal to one optimized for speech
and possibly very poor propagation or for multiple programs. This is
not a one-time choice, but something that could be changed according to
day part. Similar to the HD Radio approach, DRM can fall back to
analog, but unlike HD Radio it sends a flag that can use any AM or FM
frequency as analog backup. An alternate frequency flag can send
receivers to another digital channel as well.
Because of the scalability of the DRM technology it can fit into our
crowded broadcast spectrum and remain relatively protected as well. The
best way for a station to accomplish this would be to convert the
analog operation from dual sideband (DSB) operation to vestigial
sideband (VSB) operation. One sideband would carry a full-bandwidth
10kHz analog signal while the other sideband would carry a 2kHz analog
signal, leaving 8kHz for the digital signal. This would fit entirely
within the existing NRSC channel. More bandwidth would be possible if
overlap into the second-adjacent channel was allowed, as is the case
with HD Radio operation. In many cases, a wide-band day mode and
narrow-band night mode could be used. Not only would this solve night
operation issues but also it would be accomplished in almost
one-quarter of the bandwidth that we are now contemplating.
If the FCC were to slightly broaden its initial ruling and permit
digital broadcasting in accordance with ITU BS 1514-1, broadcasters
would have another valuable tool for the transition to digital, at
least on the medium-wave band. Those who feel they can best benefit
from HD Radio can also continue to perfect that component of the
specification. It is very important that as we move forward that the
medium-wave band remains a universal medium worldwide.
New York, NY
Dear John Battison:
I enjoyed your [RF Engineering, January 2003] article. It
brought back memories of my early ham radio days. Back in 1947, I
bought a two-meter transceiver kit from Allied Radio. This transceiver
used a 6N4 tube as a super reg. receiver and used the same tube as a
modulated oscillator/power amp on two meters. The audio section relied
on a 7C5.
Because I lived on a farm in Northeastern Montana, and I was afraid
of causing interference to another station — even though our
closest neighbor was 2.5 miles away — I built a lecher wire
system to measure my transmitter frequency. I later replaced the lecher
with a Murdo Silver absorbtion frequency meter.
The lecher system is almost a forgotten art. Your article reminded
me that there are many practices that at one time were common
knowledge, but have faded from current memory. For example, I recently
had an experience where I needed to install an inverse feedback ladder
in our vintage 10kW AM broadcast transmitter. I had to dig through
several resources until I found a reference that I could apply.
John, I would love to see an article written by you about setting up
feedback ladders. I went through my library at home and found only two
books that gave information on feedback ladders for inverse feedback
systems. One was my college text book called Principles Of Radio
by Henry and Richardson from 1947. The other book, also from 1947, is
called The Eleventh Radio Handbook.
It seems to me that information on the feedback ladder's design is
about as far gone as the use of KC for kilocycle and MC for megacycles.
John, are we really that old?
Dale Heidner, W7NAV
KGVW and KCMM
I was reading an article about the waiver signed by Artemus Records
and the RIAA. We launched an Internet radio station playing independent
country music artists and only play those that we have waivers from.
Radionashville.us is new and offering air-play for the artists who
can't receive radio play anymore and unknown artist's who need a chance
to be heard. It has been a lot of work and no profit.
We are getting waivers from every artist or label that we play on
this site. It is the only way we can stay in business. As of now, we
have a few waivers from larger labels and many from small independent
labels. I hope that some day the major labels will be calling us
instead of us calling them.
It only makes sense that record labels would want their artist's
music to be played and have as much exposure as possible. Even though
we are a new Internet radio station, we expect thousands of listeners a
week. We also offer an online store to sell the product of the artists
who can't get shelf space anymore. I feel that this is the future of
the music business. Also, we are going to make CDs available for
download for a minimal fee.
If more labels would look at every site as being a potential store,
then album sales would increase and the industry would not be having so
many problems. Also, the major distribution companies will need to
drop-ship individual CDs and set up a policy for doing this with
Harry Martin's coverage of the latest SESAC rip-off [FCC
Update, February 2003] was well written as usual, and it brings out
yet another case of legalized plunder to the detriment of
SESAC, in my opinion, suffers from a major inferiority complex,
derived from its unwanted repertoire of music that most stations would
gladly never play if they could, but strangely, SESAC would never
supply a list of its material to stations, so that stations could avoid
the expense of the SESAC license.
Now, under “super-gouge” court rulings, SESAC becomes
the latest case of bandits without pistols wherein broadcasters are
left with no options other than taking the SESAC license. What's wrong
with this picture?
To me it's wholly un-American and extremely questionable as to the
merits of our illustrious legal system; the same system that brought
you the O.J. Simpson debacle.
William S. Cook
Beware of digital media
It is unfortunate that television and radio stations have not yet
banded together to demand their share of the proceeds of the billions
of promotional value that broadcasters have given to Hollywood over the
many years. I am glad to see and read someone speak out against the
greed and avarice of the performers and producers.
When are broadcasters going to unite and take a stand? Or do we
think that problems are just going to go away, or perhaps someone else
is going to take care of them for us?
For instance, consider the horrible Internet royalties and
burdensome reporting requirements that the composers, authors,
publishers, performers and record companies have skillfully thrust upon
every radio station desiring to better serve their listeners on the
In our case at WCPE, the Internet royalty rates are 255 times higher
per-capita than those for our public radio audience. I have been
fighting for our Internet listeners for two years now, trying to seek
fair and reasonable royalty terms. I've gotten to know a number of the
players face-to-face, and I assure you, there are big problems hiding
Both commercial and non-commercial broadcasters are still dozing off
at the wheel when it comes to the consequences of the Digital
Millennium Copyright Act (DMCA) and the fees and provisions that the
recording industry and their friends skillfully and quietly lobbied to
create this law.
Broadcasters may think that they are clear for the most part, but I
venture to say that if broadcasters don't fight this monster now at the
“Internet” level, there will be real trouble.
After digital AM and FM broadcasting takes hold and the audience
expects a digital signal from their favorite local station, one
small modification to the DMCA (likely to be hidden and attached to
some benign bill) will open Pandora's box. The record industry —
angry for all these years about not being able to collect the
performance royalties that they feel “cheated out of” from
broadcasters — will have their day and their way.
Take a good look at the DMCA and the statutory license requirements
and notice that only a few words prevent these harsh terms from being
thrust upon terrestrial digital broadcasting.
The special interest groups that lobbied for the DMCA will have
their efforts rewarded when radio stations have to pay an
“ephemeral royalty fee” for the RAM copy of performances in
the buffer of our digital STL receivers — not to mention our
digital transmitters and every single digital receiver tuned to
After all, it is called the Digital Millennium Copyright Act,
and we are talking about the future of digital broadcasting.
Back in the sixties, many broadcasters donated their little 3,000W
FM stations to their local college; they didn't see a future in FM
broadcasting. Let's not repeat that same mistake by ignoring the DMCA
and the future of Internet broadcasting.
Deborah S. Proctor
Wake Forest, NC
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