GOVERNMENTS hoping to earn a fast buck by switching off analogue television
transmitters and selling the frequencies to cellphone operators are in for a
shock. Even if viewers can be persuaded to switch to digital TV, the frequencies
released will be too widely spaced to be of practical use to cellphone and
wireless Internet companies, according to a report released by Britain鈥檚
Independent Television Commission.
To be viable, cellphones and future wireless Internet access devices will
need to be mass-produced. This means they must operate on a relatively narrow
band of frequencies to make their tuning circuits affordable. 鈥淭he released
frequencies will be peppered throughout the spectrum, so there will be nothing
to sell,鈥� warns Gary Tonge, the ITC鈥檚 director of engineering. 鈥淭his is a big
辫谤辞产濒别尘.鈥�
Digital terrestrial TV is taking off fast in Britain because viewers are
given free set-top receiver boxes if they subscribe to pay TV channels. Using
the digital TV format adopted in most countries outside the US, British digital
services are transmitted on channels lying between analogue stations.
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Last March, the ITC commissioned its transmitter operator NTL and a
technology consultancy, the Smith Group, to find out how digital services could
be extended to match analogue鈥檚 99.4 per cent coverage, and so allow analogue TV
to be switched off.
The NTL/Smith Group researchers developed seven scenarios鈥攐f
mind-bending complexity鈥攂ut none of them can deliver full digital coverage
without stealing frequencies from analogue TV. So there is no chance of
simultaneously broadcasting the same programmes from analogue and digital
transmitters while viewers switch to digital in their own time. Those still
using analogue by 2010鈥攁t least 10 per cent of the British
population鈥攚ill face an abrupt change as frequencies are removed from
under their noses.
Wireless communications companies want large blocks of frequencies which are
available across a whole country. A block 155 megahertz wide has been earmarked
internationally for third-generation mobile phone networks, and this is now
being auctioned by governments in Britain and elsewhere.
The prospects for liberating a similar-sized block in the UHF waveband now
used by TV look bleak. The channels released by switching off analogue TV are
only 8 megahertz wide. They are dotted across the spectrum, and differ widely
from area to area. The report says at least 10 of the 40 analogue TV channels
should be grouped into a contiguous block to aid mobile tuning鈥攂ut this
would involve an expensive TV retuning operation well before switch-off.
Mike Short of the British mobile phone firm Cellnet says: 鈥淚f there were only
a few scattered frequencies available I鈥檓 sure we could do something with them.
But it would cost more and be less efficient.鈥�
Short points out that Europe鈥檚 GSM cellphone system is a global success
because international agreement on frequency allocation allows 鈥渞oaming鈥�:
handsets from one country work in others. 鈥淭his means GSM handsets get better
and cheaper all the time,鈥� he says. So similar agreements on allocation of the
TV channels would be necessary.