of the XXIst century
the end of the XXth century we entered into the Information Age, and
we were the witnesses of the widespread of digital technologies like
the computer, the CD, the GSM, the DVD, the MP3 and other digital
packet. Suddenly the radio of our parents looked old-fashioned.
Imagine : it was made in the last century, Hi!
a similar way, and as surprising it was, in September 1996 the Digital
Radio Mondiale, DRM for short, emerged from an informal meeting in Paris
(F), between some of the large international broadcasters and broadcasting
equipment manufacturers. These
included representatives from Radio France Internationale, TéléDiffusion
de France, Deutsche Welle, Voice of America, and Thomcast.
meeting, a consensus emerged that unless something was done, the days of
national and international broadcasting in the AM bands below 30 MHz were
DRM Consortium formed in 1998 when a small group of pioneering
broadcasters and manufacturers joined forces to create a universal,
digital system, DRM, for the AM broadcasting bands in HF, this wide band
of frequencies including short waves, medium waves and long waves. Since
then, DRM has expanded into an international consortium of more than 70
broadcasters, manufacturers, network operators, research institutions,
broadcasting unions and regulatory bodies,
with members represent more than 25 nations. Today DRM’s membership is
rich in its diversity, with members live in countries as varied as
Australia, China, Ecuador, Finland, France, Germany, India, Japan,
Luxembourg, Nigeria, Spain,
Tunisia, the U.S.A. or the United Kingdom.
not a registered trademark. This is a standard entered into force as
of January 30, 2003. At this time the International Electrotechnical
Committee (IEC) gave DRM its highest stamp of approval, the
International Standard : IEC 62272-1, following the DRM specifications
PAS 62272-1 approved in 2002.
DRM antennas at
Junglinster, LX. 600 kW on 234 kHz and 70 kW on 6095 kHz
in 2002 DRM received endorsement by the ITU for all three
broadcasting bands (SW, MW and LW) below 30 MHz. The new ITU
Recommendation BS1514-1 states that DRM is an ITU-R Recommendation
for all the broadcasting bands spanning 150 kHz to 30 MHz. No other
digital radio system has received such broad recommendation and for
all three bands by the ITU.
the European Telecommunications Standards Institute (ETSI) published
a Technical Specification of the DRM system in September 2001. The
document is called ETSI TS 101 980 V1.1.1 (2001-09) and define the
DRM system specifications.
new standard does not mean that DRM is reserved to broadcasters and
fixed services. On the contrary ! This standard means that DRM is
non-proprietary, with the ability to use existing frequencies
and bandwidth across the world, and
therefore interest much the radio amateur community.
DRM signal fit in a bandwidth of about 10 kHz (against about 3 kHz
for SSB phone), although there is a
wide version that spreads over 20 kHz and a narrowband version 5 kHz
wide, the wider offering the best audio fidelity.
DRM uses the COFDM
(Coded Orthogonal Frequency Division Multiplex) modulation. The
signal is modulated on a great numbers of carriers (max. 460) thanks
to the FDM technique. This allow an emitter to avoid problems with
the differents paths that a wave can follow to reach a receptor.
Additionally DRM can integrate data and text. To code the audio
signal DRM use several systems : MPEG4 AAC when there is a mix of
speech and musical content and MPEG4 CELP when the signal contents
only a speach without musical content. DRM
is in fact an application of DAB. This
concept is used in the DVB standard (Digital Video Broadcasting)
amateurs also use digital audio and video !
broadcasters, hams actively participate in experiments
developing the use of digital voice and video over ham techniques, and
ARRL in particular has created a Digital
Voice Working Group in that purpose.
digital transmission have many advantages of analog
transmission : the reception is error free, noise-free and
the listener can potentially receive simultaneously audio,
voice and data. There is only one drawback, the bandwidth
occupies 10 kHz or more vs. 3 kHz for SSB phone.
get a quality voice signal data rate must be of at least
3600 bits/sec or higher. The modulation uses sophisticated
formats like orthogonal frequency-division multiplexing
(OFDM) with multiple subcarriers modulated at low bit rate
using phase-shift keying (PSK), quadrature amplitude
modulation (QAM), etc. This modulation is combined with
error detection and correction, so much techniques necessary
to transmit signals in a dispersive media as HF. The main
advantage is to be able to transmit on HF digital
information at a rate that can reach 5400 bits/sec.
less known due to its young age, the Digital
Amateur Radio Television (DATV) is the digital evolution of
SSTV. It will be on board the European Columbus module of
ISS from 2007 in framework of ARISS activities.
to now broadcasters use several standards, DAB (Digital Audio
Broadcasting) using the Eureka-17
standard for FM broadcastings and Ibiquity IBOC (In-Band On-Channel)
for AM broadcastings, recently activated by WOR Radio in New York.
Both standards are used worldwide but DRM
appears as the only one standard recognized internationally for HF
will progressively replace classic AM broadcastings, and will become
the "digital AM". Indeed, this new standard offers a
higher listening quality : RFI, noises and fading practically
check : DRM
to DRM !
samples of two speeches (UK and F), a sound and a
demonstration broadcasted by DRM stations on shortwaves (.MP3
of 443 KB, 378 KB, 1.4 MB and 1 MB).
quality of signals can be modulated depending of the information to
transmit, i.e. the language of the transmission for a speech.
Without being equivalent to an audio CD, DRM offers the same
listening comfort and quality as FM. We can quasi speak of HiFi
the FM band is limited between 88 - 108 MHz and is heavily occupied
by more broadcasters than there are channels available. For ITU
authorities, assigning bandplans worldwide is became a true
challenge when they must satisfy requests from all services
involved. In this context, DRM
is an interesting alternative. According
the consortium, DRM will revitalize the AM broadcasting bands below
30 MHz in markets worldwide. In parallel the regulation has to
evolve to take in account this new broadcasting mode.
emitters working in short, medium and long waves count by thousands
as Klingenfuss could
confirm, and these companies invest much money in their installation
to ensure the best coverage over their country or abroad. Hopefully
DRM allow the reuse of these installations with some
the listener, DRM consortium insists to the fact that
receivers have to be at low cost to attract customers, the reception
quality must be improved without change to existing listening habits
(same frequencies, same listening conditions - fixed, portable and
mobile radio - and same listening environment - indoors, in
cities, in the country...), receivers must yield low energy
must be easy to use and tuning, programmes various and taking
the full capabilities of new digital features.
flat-top waveform of a DRM broadcast from Deutsche Welle radio recorded
with Merlin's Communications software provided by DRMRX.
advantage for the manufacturer is that DRM increases
the longevity of AM technology while opening new opportunities.
This new technology also increases the market potential for
transmitting and receiver systems. And last but not least, it
optimises return on investment and other financial
time, DRM estimates that people will replace about 2.5 billion
receivers with digital AM receivers !
last for the broadcaster DRM ensures the continuing use
of existing transmission systems and a more efficient use of
existing frequency planning as well as a better control of
coverage area and short-term flexibility.
Of course the
broadcaster will provide a better audio quality for listeners,
wherever they live, and will probably see an increasing of his
audience interest, resulting from audio quality improvement
and additional services. In fact all active participation in
the development of DRM gives the opportunity to contribute to
the implementation of "digital AM" radio.
the ambitious project of its conceptors, DRM offers the opportunity
to broadcast textual messages like does RDS in FM. It will also
automatically switch of frequencies to help users to continuously
listening to a program whatever the propagation conditions. At last,
DRM will support transmissions in mono, dual mono or stereo. This is
already the second generation of DRM, which first products were
available at Christmas 2003.
will allow to answer to the increasing demand from all services
working in HF. But it has also to take into account a time of
transition for all classic AM users. It is out of question to take
new channels in a spectrum already widely saturated.
DMR has decided temporary to allow emitters to work in both analog
and digital in the same channel, this is the "simulcast".
Depending the evolution of markets, DMR will progressively open all
the channel to digital transmissions, this is "multicast",
what will increase drastically the emissions quality, the numbers of
new services available and maybe to... multimedia.
your old HF receiver to DRM
please everybody the first digital receivers will have to support
both analog and digital broadcastings. But for our concern, it is
not necessary to sold our current AM radio to buy an "AM
digital" stamped DRM. Indeed, we can modify any recent analog
radio, including you old HF receiver, to make it compliant with DRM. The main modification consists
to widen the Intermediate Frequency (IF) bandwidth to about 20 kHz. Any commercial front-end with an
IF of 455 kHz or even 10.455 MHz should be usable by adding a 455 kHz
(or 10.455 MHz) to 12 kHz adaptor (assumed the receiver bandwidth is sufficient for a DRM
signal). This interface is called a downconverter.
that your receiver is upgraded, you need a decoding DRM software and
a computer. Today DRMRX
through the project "Dream" sells a
processing software under the GNU General Public License for 60 €
or $70. Due to the intensive FFTs computations requested to
synchronize the frequency, you need a
Pentium PC running at 500 MHz or faster equipped with a sound
card to process the digital signal. Documentation of receiver
modifications for DRM reception can be found on DRMRX website.
of the first receiver to use this hybrid technology is ICOM PCR-1000,
a pocket stereo shortwaves receiver able to receive AM, FM, USB, LSB
and CW modes. It comes with a serial and a BNC port to link it to a
computer running the DRM processing software (e.g. Dream
PCR). Decoding is automatically done
thanks to the optional DSP module. To work properly you have only to
set the ICOM receiver in USB mode via the DRM software, set the filter to 50 kHz and shift the receive frequency
12 kHz up. You must switch off the AGC and sometimes the attenuator,
the squelch and the optional DSP by pressing some buttons on the
graphic user interface (GUI) reproducing a typical DRM receiver
as displayed below.
WR-3000i GUI is a typical DRM software running on
a PC. This one is tuned on VHF bands. At right the
GUI of the WinRADIO card G303 tuned on 6095 kHz
where Radio Luxembourg expriments its first DRM
PCR software count among
competitors of WinRADIO.
time running, new manufacturers are involved in this technology and
their products are always appreciated. WinRADIO,
an Australian manufacturer, sells several radio cards like G-303i to install in a PCI slot
of your computer ($500). A DRM demodulator is currently programming
and soon available as a plug-in. This digital radio is able to
receive all frequencies between 9 kHz and 30 MHz in most modes
(AM, FM, USB, LSB, CW). Other DRM cards cover V/UHF and SHF frequencies up to... 4 GHz
if necessary !
manufacturers begin to sell DRM radio receivers to name Coding
Technologies, Mayah (DRM 201D), Ten-Tec
(RX-320D), and FhG
AOR Japan (AR7030).
in emission !
2005, FlexRadio Systems,
an US manufacturer, sells the first software defined transceiver
compatible with amateur modes (SSB, CW, AM, FM, RTTY, PSK) and DRM : SDR-1000. It works on both HF and VHF
bands with an output power of 100 W in HF and 50 W in VHF. It
looks like to a passive peripheral, a black box standing on your
desk totally controlled
by a software named PowerSDR, for now only accessible to computers running
Windows XP Home Edition with Service pack 2. It price starts at
$1375 (without PC, sound card, antenna, antenna tuner and
shuttle-pro controller. Fully operational with a computer and a
dipole or a vertical, it costs
encourages programmers to enhance the open-source code. The GDI is
written in C# (C-sharp) while the DSP is written in C (shared source with a Linux
version). The PowerSDR source code is available free from the
FlexRadio website's download page.
future is really digital !...