The Channel | 2003 | September

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attractive level by the time that the first receivers become
available. Broadcasters and transmission operators also have
advanced plans for making the investment in transmission plant
which will enable this progressive increase in broadcasting hours
in the years ahead. So it would seem that the wind is set fair for
a successful outcome. However plans being implemented by
electricity utility companies in some countries, in particular
Europe and the US, could ultimately lead to the ending of
broadcasting, or at least the ability to receive broadcasts, in
most of the AM bands in these countries.
Power lines cloud the future
A number of power utility companies in Europe and the U.S.A.
are proposing to use their existing cable distribution systems to
provide broadband Internet services to existing customers. They
propose to do this by providing a high-speed data connection
to the Internet at a point near to consumers’homes. They would
then provide a connection between this point and the consumer
by superimposing a high-level high speed data signal onto the
existing power distribution cabling, often at the local substation.
This distributed signal has a spectrum which continues up into
the SW bands. This provides the subscribers’ homes with a
permanent connection to the Internet.
Because the power cable is not designed as a communications
cable and has a high level signal (the mains supply) already on
it, it requires a high level signal to be superimposed if the data
signal is to be successfully retrieved, some distance away, at
the customer’s home. Also due to the poor communications
characteristic of power cables, particularly at higher frequencies
up towards 15 or 20 MHz (i.e. into the SW bands), there is a
considerable level of radiated signal close to the cable. There is
extensive signal radiation from the street cable, if not buried,
and from the domestic cable, which is used as the means of
Internet distribution to the connected PC(s).
As a consequence signals are radiated from these power
cables within the SW broadcast bands and other bands
such as the aeronautical and amateur radio bands) at a
level which can render reception close to the home and
inside the home of very poor or unusable quality. In other
words the system pollutes the radio frequency (RF)
spectrum to a level well above the normal background
level. Unfortunately, for the power company, operating
PLC/PLT systems at signal levels where this pollution does
not occur renders them incapable of providing satisfactory
Internet service.
However this pollution problem has so far not been sufficient
deterrent to change the minds of the utility companies. National
standards are already being set in some European countries,
which will allow these signals to cause significant pollution to
the SW RF spectrum. Nevertheless some of the power utilities
are even calling for these existing limits to be revised upwards,
as their systems do not yet work entirely reliably.
Within the European Union, the European Commission has
decided to call for submissions from experts in the field before
making a determination on whether these systems should benefit
from existing or more relaxed standards. Indeed the question is
being raised in the EC as to whether it is worth sacrificing
reception and use of the AM bands in order to allow the rollout
of PLC/PLT systems to increase competition and accelerate
European broadband Internet use. This in turn raises questions
as to the obligations of European Administrations under the
ITU to protect this spectrum. As all theseAdministrations have
agreed to abide by what is, in effect, a treaty on spectrum use it
would set a dangerous precedent if the EC were to overrule the
continued obligations for protecting the spectrum for which its
Member countries had signed up.
Notwithstanding the imminent danger posed by PLC
developments, all the pieces of the DRM jigsaw are in
place, or close to being in place, which should see the
successful introduction of DRM services to the mass
market. The expected availability of first consumer
receivers towards the end of 2004 will provide the real
test of whether DRM is a system destined to succeed and
keep alive broadcasting in the AM bands for another fifty
years. If so the future of the international transmission
business should be assured for companies like VT Merlin
Communications.
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