Australian companies will pay millions, possibly billions, of dollars in coming years for a weightless, invisible asset discovered by physicists more than 120 years ago - radio waves, the Age wrote this week.

And this week’s switch to digital television in Mildura was the first step to freeing up a large slice of the radio-frequency spectrum and giving the government a chance to change the distribution of spectrum. But tension is building between telecommunications carriers and the television broadcasters that already occupy key parts of the spectrum.

Mobile broadband is the fastest-growing telecommunications product, and carriers are expected to pay hundreds of millions of dollars when the spectrum becomes available.

Another big cost to mobile phone carriers this year will be renewing their mobile spectrum licences. Negotiations over the price are still going, but Communications Minister Stephen Conroy said earlier this year the government would seek a fee that ''reflects the scarcity and value of this important public resource''.

Radio-frequency spectrum is a limited resource, and governments have the power to decide how much spectrum goes to television signals, to transportation, to mobile broadband, to defence, and to commerce.

The spectrum was discovered in the late 19th century when physicists found they could adjust the frequency of naturally occurring electromagnetic radiation waves to create signals.

In 1896, the first long-distance radio message was sent by Italian inventor Guglielmo Marconi and in 1903 the International Telecommunications Union held its first conference on wireless technology. The ITU is still the peak forum for co-ordinating radio-frequency spectrum allocation.

Australia's telecommunications companies at the moment have their eyes on two opportunities to grab more spectrum - the space used by analog television signals, and the 2.5 gigahertz spectrum used by television stations for live crosses and news feeds. The ITU has stipulated that every country use 2.5 GHz for the next generation of mobile technology, known as long-term evolution (LTE). Telstra can bid for this spectrum only if it completes a deal to transfer fixed-line customers to NBN Co's fibre network.

The 2.5 GHz spectrum can carry more information for short distances, which makes it perfect for metropolitan mobile broadband, while the spectrum now used by analog television, 600-800 megahertz, carries further and could be used by customers in rural areas.

But broadcasters are reluctant to move out of their 2.5 GHz allocation, while telecommunications companies are desperate for a decision so they can plan their LTE rollouts. Using the same frequency as in other countries would lower LTE handset and infrastructure costs.

It is up to the Australian Communications and Media Authority to decide which service the public needs most.

''Demand for mobile broadband is going through the roof,'' the chief executive of the Australian Mobile Telecommunications Association, Chris Althaus, said this week.

''New spectrum is going to be increasingly important to the industry to service demand, so there is going to be intense interest in the digital dividend.''

AMTA is funded by the mobile industry to represent their interests in Canberra. Althaus said that once the Communications Minister finalised allocations, it would set the industry up until 2020.

''Given the projections of growth for mobile broadband, there is no doubt that new spectrum is required,'' Althaus said. ''If there is suitable spectrum available that can be used more efficiently and effectively, then the mobile industry will almost certainly be interested in that.''

Conroy last week announced that 126 MHz of spectrum would become free from 694 to 820 MHz once all analog television signals were switched off, and this spectrum would be auctioned in late 2012. He emphasised how valuable the frequency was for super-fast mobile broadband services. The proceeds of the auction have been dubbed the ''digital dividend''.

But the free-to-air television industry argues that giving away its spectrum puts businesses under pressure from cable and internet television. The ABC warned that the money reaped from the digital dividend should not be given more weight than the public benefit of a broadcasting service.

''There is a very real risk that Australian free-to-air television will indeed be adversely affected, as its ability to deliver new technologies and services that meet audience expectations will be hampered by a lack of spectrum,'' the ABC's submission to ACMA said.

Last week's announcement was a win for the telecommunications sector over broadcasters, and ACMA must soon decide what happens to the 2.5 GHz spectrum.

Ericsson Australia's Kursten Leins said the telecommunications industry needed certainty to grow. Operators needed to know years before they launched a service what type of equipment would work on the frequency and how much data they could transmit, he said.

By 2020 voice calls would be a fraction of the information transmitted over the spectrum allocated to mobile broadband, and media companies and developers were likely to bid for spectrum to provide yet-to-be-invented services, Leins said.

One indication of how much carriers would be willing to pay for spectrum is ACMA's March 2001 auction for spectrum for 3G services - that auction raised $1.17 billion