If there is a revolution in media, it’s a local revolution, one led by the internet, and it’s dramatically changing how media is bought and sold in local markets and who gets what share of those ad dollars.

Businesses that could never afford to advertise before are doing so now, and the choices of how to deliver their message have considerably broadened. It used to be the old triumvirate: newspaper, TV, radio. And maybe there was a local alternative weekly.

Now there are those as well as well as local cable and a raft of internet sites, some but not all attached to traditional media outlets.

By all rights, local radio ought to be getting a hefty share of those ad dollars, considering how long it’s been around and the legions of well-connected local sales people it has already on the ground.

But it’s not. In the grab for local online ad dollars, radio is struggling.

Since 2004 local online advertising has grown from $2.1 billion to more than $13 billion, according to Borrell and Associates, which tracks local media spending. Of that figure, pureplay internet sites are getting about 50 percent, while newspapers are taking another 25 percent. TV stations are getting close to 10 percent.

Radio is getting what’s left, only 1.6 percent. By contrast, traditional radio grabs more than 7 percent of the share of local ad dollars.

There’s an upside to those numbers, as the Radio Advertising Bureau notes in its year-end 2009 report. Radio has seen its digital revenue increase in seven of the last eight quarters, and rather smartly. It’s grown by nearly 66 percent since first-quarter 2008.

But the question remains, why isn’t radio getting more?

There’s not just one answer. Part of it has to do with radio coming late to the game. But it’s also done a poor job of seeing the potential of online and then selling the value of advertising on station web sites to customers.

In part radio’s slow start was due to a reluctance of station owners to begin streaming audio. Though a logical brand extension, there were concerns about bandwidth costs as well as music licensing fees and union issues involving digital rights of the talent.

But a bigger issue appears to have been the reluctance of radio stations to step beyond their core competence, which is selling advertising for radio content that goes out over the airwaves.

“Getting digital dollars is not our core competency. We are experts at selling radio,” observes Lance Richard, vice president of digital sales for Entercom Communications.

No surprise then that radio sellers have been slow to learn the new digital language. Borrell reports that of the 17,000 local radio sellers in the U.S., just over 1,000 have had digital sales training. In comparison, 15,000 of the 30,000 local newspaper sales reps have received digital training.

One effect of that lack of training, seen in other media as well, was to undervalue online as a means of connecting with consumers, in effect giving it away as part of a larger deal.

“We’ve been using digital as added value to get larger shares of radio dollars,” says Richard. “We never established value for our digital inventory.”

Another challenge has been for salesmen to get their minds around the idea of talking not about the technology but how that technology can better serve the advertiser, to talk the language of marketing.

Clients don’t really care about the technology.

“What clients want to know is how you are going to help them sell that car or haircut,” says Richard. “When we come in with an integrated solution, that’s when their eyes light up.”

All this is beginning to change. More and more, radio companies are coming to see the revenue upside of digital, and they are investing time and resources into building up the digital end of the business and selling integrated ad packages.

The challenge now is catching up. Local online was a wild west show a couple of years ago, driving by huge yearly increases in ad spending. But those days are over. There’s far less growth and more salesmen on the ground. Local businesses are also a lot shrewder about internet advertising. That makes them harder sells.