The Channel | 2003 | September

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south-west England) which provide daily DRM short wave
transmissions for a number of international broadcasters, and
the purchase and installation of a new 200kW Nautel MW
transmitter at the Orfordness medium wave site (on Britain’s
east coast), which provides several hours per day of DRM
transmissions into western Europe on 1296kHz. Work is also
continuing on the adaptation of a third 500kW Marconi short
wave transmitter at Rampisham. However this can only be the
early stage of what will be a long-term programme of investment
in transmitter conversion or provision and in the infrastructure,
which will be needed to support a fully integrated DRM
transmission system across sites spanning the world.
The introduction of a digital transmission system for international
broadcasting in theMWand SWbands has profound implications
not just for the transmitters and receivers but also for the
transmission chain and the monitoring and control of the
transmission chain. The introduction of a system which can
support audio quality close to FM mono on SW and FM stereo
on MW means that the quality of studio production needs to be
equivalent at least to that for FM and that distribution to the
transmitters must also reflect this. Otherwise listeners will not
fully benefit from the performance improvement, over analogue
transmission, of which the system is capable.
The introduction of the DRM system also provides the
opportunity to transmit a limited amount of data to the listener
along with the audio. This data can be associated with the
transmitted programme, such as an electronic programme guide
(EPG) carrying details on current and future programme content
together with transmission frequencies and schedules, or other
dissociated data, such as weather forecasts, for example. All of
this data must be assembled at the head-end and integrated into
the DRM multiplexes so that it is transmitted on the correct
transmitters at the right time. This is not something that has
previously been a characteristic of MW or SW broadcasting
and its introduction will require care and attention to detail if it
is to enhance, rather than detract from, the listeners’ experience.
Why the need?
Of course it could be asked why so much effort is going into
updating what to some might seem an old fashioned and outdated
technology. This can be answered by looking at the unique
properties of SW, MW and LW broadcasting which cannot all
be provided by competitors such as the Internet or a satellite
delivery system.
Firstly, transmissions in these bands can provide coverage over
large geographical areas at a relatively low capital outlay and
with low risk and high security. The transmissions can also be
received both within buildings on portable receivers and in
moving vehicles. Because both the transmission frequencies
used and the data rate transmitted are low, the power
requirements of the receivers can also be modest, leading to
useful battery lifetimes and therefore reasonable economy. The
transmitter plant can also be easily maintained as it is all
terrestrially based.
The cost of reaching listeners via radio transmission is largely
fixed and therefore the cost per listener declines the greater the
number of listeners. In many cases it will prove possible to
convert existing transmitters to carry DRM transmissions so
that the incremental cost of adding the capability, at least at the
introductory stage, is quite modest. Several hundreds of millions
of people in the world are accustomed to receiving news and
information via small low cost portable AM radio sets and the
number of such radio sets sold to date runs to well over one
billion. This means that there is a huge potential market for
receiver manufacturers to tap if they can produce DRM capable
receivers at an attractive price. If so the difference in quality
between the current analogue services and the DRM digital
services is immediately obvious to listeners and provides a big
incentive to trade up to a new DRM capable receiver.
Market forces
However, any strategic analysis needs to examine what might
prevent DRM succeeding in the market place and replacing the
current analogue AM transmission system. Certainly the price
of consumer receivers will be crucial but current work to develop
a first generation chip or chip set is well advanced and this
should lead to first consumer receivers appearing on the market
in late 2004 or early 2005 with costs declining as further
generations of chips lead to lower receiver prices. Also crucial
will be the number of DRM broadcast available on air to attract
listeners into making an investment ion a new receiver. It is
worth noting that both the number of broadcasters and the length
of transmissions are increasing and these should reach an
From left: the Nautel medium wave
transmitter at the Orfordness transmitting
station in England; high voltage power lines
- potential problems for AM broadcasting;
Peter Jackson
36 | the channel
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