IN four years, digital radio has spread across five Australian capital cities and almost tripled the number of radio stations available.
It has attracted an audience of 1.5 million listeners and appeared in more than one in 10 homes and 14,000 cars.
But Australia's regional centres and some capital cities are still missing out on the technology. Commercial radio's governing body says a $500 million investment is required to spread the broadcasts further.
A federal pre-election campaign is seeking a commitment from both sides of politics to make digital radio a national proposition. A minimum of 20,000 signatures is needed to put the proposal to the federal political parties.
But even the industry doesn't expect a financial commitment until 2015.
Digital radio broadcasts began in Australia in May 2009 after a long campaign.
First introduced in Perth, followed by Melbourne, Adelaide, Brisbane and Sydney, digital radio in DAB+ format offers clearer, CD-quality sound, consistent reception, and the ability for stations to send text and pictures with broadcasts. Song titles, weather forecasts and competition details now often show up on digital radio screens.
The technology also allows existing providers to broadcast more radio stations.
The ABC, for example, produces stations dedicated to jazz, country and independent acts, while new stations such as Smooth FM, Radar, NovaNation and Mix '90s have been created for the medium. But only residents in five of Australia's capital cities can tune into these broadcasts.
Canberra and Darwin listeners receive a limited number of stations as part of low-powered trials that began in 2010. Regional centres miss out.
Commercial Radio Australia chief executive Joan Warner says digital radio needs to be a national proposition for listeners and digital radio manufacturers to have confidence in the technology.
"We're working towards getting a policy commitment to roll it out nationally," she says. "We have a campaign on air in all regional areas, just letting listeners know that they're missing out.
"The campaign has only been on air for three weeks and we've already attracted more than 8500 signatures."
But Ms Warner admits a national financial commitment to digital radio is not a modest request. Introducing the technology to 95 regional centres is forecast to cost $500 million over 16 years.
The more than $30 million annual sum would go towards transmission towers, antennas and operational costs - half of which would pay for ABC and SBS broadcasts.
"Everyone is saying that digital radio has to be rolled out nationally, but the state of the Budget means that we're not expecting to see a commitment until the 2015 Budget," Ms Warner says. "What we really want from the Government or the Opposition is a publicly stated policy to roll this out."
In the meantime, the fourth anniversary of digital radio in Australia shows the technology has come a long way.
While the cheapest DAB+ radio cost $179 at its launch in 2009 and averaged $300, digital radios can now be purchased for less than $50.
Dick Smith audio category buyer Shay Stearnes says high demand and fierce competition in the market pummelled prices, but consumers are now proving they are willing to invest in high-quality digital radio receivers.
But Mr Stearnes says consumers need greater education on the benefits of digital radio and its footprint for the technology to become a best-seller.