The situation highlights what insiders say has been a mounting problem in the industry: a lack of any type of infrastructure for supporting talented up-and-comers.

“The top talk-radio hosts are not replaceable; it would be like trying to replace a best friend,” said Kraig Kitchin, the former president and COO of Premiere Radio Networks and founder of management firm Sound Mind.

“It’s hard to duplicate a unique personality,” added Michael Harrison of Talkers magazine, an industry trade paper that boasts 10,000 subscribers who pay $75 a year.

Sirius XM says that talk is so popular among its 20 million subscribers that it has added several niche stations through the years, like OutQ for gays and lesbians, the Catholic Channel, the Doctor Channel and Book Radio.

Still, in the world of spoken-word radio, there are just a handful of superstars, the big dog being Rush Limbaugh, who attracts more than 15 million different listeners a week, according to Talkers. He’s followed by Sean Hannity (14 million), Glenn Beck (10 million), Mark Levin and Michael Savage (8.5 million apiece) and Dave Ramsey and Schlessinger (8 million each).

“After those seven, who are on 600 stations apiece, you’ve got 25 people you can rank next,” quipped Al Peterson, publisher and president of NTS MediaOnline.

Talk’s rising audience has been a bright spot in an industry dealing with an advertising recession and competition from the rise of digital music. Revenue in the radio industry fell for four consecutive years until recovering with a 6% gain during the first half of this year to $8.24 billion, according to the Radio Advertising Bureau.

Arbitron crowned the category of “news/talk/information” America’s No. 1 format in its most recent “Radio Today” report, which says that — in no small part because of a historic presidential election that had newbies tuning into talk — the genre garnered 12.6% of the radio audience. That’s up from 10.7% two years earlier and one-tenth of a percentage point ahead of the runner-up, country music.

At 2,634, news/talk/information also leads all 57 categories in terms of station count. Harrison estimates that about 100 million Americans listen to some form of talk radio, be it political, sports, finance, medical, relationship, comedy or what have you.

But insiders say that if talk is to continue its roll, it needs to identify and groom hosts who can attract Limbaugh-size audiences at reasonable salaries while learning not to skimp on the marketing of as-yet-unproven talkers.

It used to be that talkers would hone their craft during weekends and off-hours and in small markets, then work their way up. But cost-saving measures have led to filling those hours with syndicated shows.

“This is exactly the right time to promote new talent because nobody else is,” said David Katz, a former agent for Phil Hendrie, Tom Leykis and Jay Thomas who’s now CEO of the Elvis Duran Group, the company behind Duran’s syndicated radio show.

“There is no clear next generation, and that is very sad for the industry. Radio has a chip on its shoulder because it’s treated like a bastard industry in the shadow of film and TV. The only way to lift it is to celebrate the talent.”

Just don’t celebrate it too much, counter other insiders who prefer to remain anonymous — otherwise, you might create more aberrations like Limbaugh and Stern, who command such massive salaries that there’s little left over for partners to claim as profit.

Limbaugh earns an estimated $58.5 million annually, amounting to almost $4 a listener, and Sirius XM pays Stern and company $100 million each year, of which Stern gets 80%. Lesser but still popular talk-radio talent earn a lucrative but far more modest 10 cents-$1 a listener.

Like all performing arts, breaking into talk radio never was a matter of simply earning a degree from the Columbia School of Broadcasting and mailing out tapes to perspective employers, notes host Michael Medved. Today’s stars arrived in myriad ways.

Stephanie Miller, for example, is one of the nation’s most popular liberals in political talk, which is dominated by conservatives (the Top 10 talkers all lean right). Miller was a theater major at USC and got her radio start as a wacky music DJ before she had much interest in politics. Asked how one might break into the industry these days, she quipped: “There’s no more room for you, kids. Good luck.”

Medved, a Top 10 host with nearly 4 million listeners, got into radio after appearing on numerous shows to promote his books. He substituted for Limbaugh for the first time in 1993, got his own show in Seattle three years later and went national the year after that.

“To be successful, you have to be emphatic, intriguing and engaging without being unduly repetitive,” Medved said. “The challenge is keeping it fresh. If there are listeners saying, ‘I got it already. I’ve heard you talk about this for five days,’ then you’re risking your audience.”

Added ESPN and ESPN Radio’s Scott Van Pelt: “I was a guy on TV who thought, ‘How hard can this be?’ “But it’s so difficult to flush out topics and come up with opinions the audience hasn’t already heard.”

Said Andrew Breitbart, the conservative new-media mogul who substitutes for several national hosts: “Anyone who thinks doing three hours of radio is easy is insane. The first time I did it, I had a panic attack.”

That talk is so difficult to do well is all the more reason for the industry to support something akin to a talk-radio farm club. That it hasn’t is surprising given the financial potential.

Peterson of NTS MediaOnline (the NTS stands for news, talk, sports), is attempting to rectify that with his three-day Talk Media Conference & Talk Show Boot Camp that begins Tuesday in Marina del Rey, Calif. Headline speakers are Beck and Ramsey.

Peterson expects 250 radio pros will attend the event, paying up to $400 apiece for all-access passes. That the event is expected to be well-attended and attract top-notch talent is a testament to the industry’s strength.

“Music is a nightmare in radio, but NTS hasn’t been immune,” Peterson said. “They’re not stand-alone channels. They’re part of a cluster that includes FM music stations. Executives will tell you that NTS is far more profitable than their music cluster mates, even though NTS is more expensive.”

Every talent deal is different, but morning-show host Duran offers a glimpse into how the model now works. Duran and his 10 or so sidekicks are heard on 34 stations nationwide. Depending on the size of the market, a station might pay $25,000 a year or 10 times that much to license the show. Then Duran’s company might take a minute of advertising an hour and the station would get the rest, typically 12-14 minutes.

His show is on four hours a day. If a station can sell an ad for an average of $500 per 30 seconds, the show will generate more than $6 million in annual revenue at that one station.

Insiders say only the top talkers can negotiate both a license fee and an advertising-revenue share. A station might have to surrender as much as 33% of its ad time, plus a hefty fee, if it expects to carry Limbaugh.

Some elite talkers — Hannity, for example — might opt for a big ad-share in markets where ratings are high because he follows Limbaugh, whereas he might take a hefty license fee and little or no ad-share in markets where he doesn’t follow Limbaugh.

Ad rates oftentimes are healthier in talk than in music because they are so effective, given that an audience tunes in to hear a trusted opinion, and that trust carries over to the commercials.

Mostly, national talent is culled from the best of the local talkers. Kitchin, the longtime radio executive, says that when a local host begins to garner an audience 30%-40% higher than is typical at the station, he knows the host could be ripe for the national spotlight.

Hendrie, whose comedy show involving fake guests is on 115 stations, says penny-pinching executives who lack vision is a problem, and that has led to boneheaded decisions like hiring rock stars, politicians and former police chiefs to host shows.

“Non-media doing radio is interesting but by and large doesn’t work,” he said. “We need professionals in our field, not David Lee Roth and Fred Thompson. Who’s next, Sarah Palin?”

Hendrie said former San Diego Mayor Roger Hedgecock is an exception who is doing fine talk radio. But even giving Bill O’Reilly a radio show was a mistake.

“He never touched Rush Limbaugh, and that’s what he set out to do,” Hendrie said. “O’Reilly’s great on TV, but on radio you need to ad-lib.”

Hendrie bemoans “a particular type of amateurism nowadays,” and even long-time radio executive Mel Karmazin, now CEO of Sirius XM, doesn’t impress him much. The company has lost more than $2 billion since its inception.

“Last I heard Karmazin was supposed to be this radio genius,” Hendrie said. “We need a new generation of executives.”

Asked whether he’d move his show to Sirius XM, Hendrie quips: “No. I like to get paid.”

Nowadays, radio talent can be plucked from the Internet. So far, though, it seems as if it’s going in the other direction, with established hosts adding online to their repertoire or, in some cases, going online-only. Adam Carolla is the most prominent example.

After CBS let him go last year, he delivered his online “State of the Radio Industry” rant, and his podcasting career was off and running. Sixteen months into it, he’s turning a profit, thanks to a couple of six-figure advertising deals and the more intangible benefit of pitching his upcoming book and his live appearances on his podcast.

“Advertising is a part of it, but it’s also a way to communicate and thus monetize,” Carolla said.

He puts out a 90-minute podcast five days a week that contains no more than four minutes of advertising. His audience downloads the free podcasts 1 million times a week.

“I’m not here to bash terrestrial radio,” Carolla said. “The bottom line is, they have overhead. We can do it all from my studio in Glendale for pennies on the dollar. I don’t know how they can compete.”

Carolla says his staff of about a dozen people have been working “on good faith,” but by year’s end he expects to give them a raise.

Asked to update his state-of-the-industry address, Carolla describes his appearance on a Denver morning show: “A congenial guy and gal did a lot of, ‘OK, it’s 27 minutes after the hour.’ And I said, ‘Who doesn’t have a clock? Seriously, it’s built right there into the alarm.’

“I sat there for an hour, and I was on the air for six minutes. I realized that I didn’t really talk about anything. More importantly, the hosts didn’t talk about anything.

“I get it. It’s 8:51 and Adam Carolla is with us, and they have the most traffic reports — they’re wasting our time!”

Are there any competitors out there Carolla likes? “I hate to sound like an asswipe, but I never listen to anyone’s podcast, including my own,” he said. “I’m not a computer guy.”

He’s in the majority, actually, not listening to podcasts, but that’s changing. The number of Americans who listen to radio online each week has doubled in five years to 43 million — or 17% of those more than age 12 — be it the Web-only variety or an online stream of a traditional station, according to a study this year from Arbitron/Edison Research.

Tammy Bruce is another host who ditched terrestrial radio, in her case after 16 years, so she could “go commando,” her term for online radio.

Bruce, though, shuns advertising and charges $5 a month for premium subscriptions. The first two hours of her show are free and the third is for subscribers, who also get access to an on-demand archive.

With no advertisers, “there’s no Gestapo to smother you,” she said, invoking the N-word controversy that engulfed Dr. Laura recently. “I’m free to talk about politics in a framework where I can’t be threatened.”

Bruce said her “aha moment” came shortly after Barack Obama was elected president. She played the theme song from the movie “Shaft” as she expressed her opinion that the country had been shafted, and an executive with her syndicator, Talk Radio Network, told her to knock it off.

“They thought it was racist,” she recalled. “Radio is a medium that requires bluntness. If I’m supposed to adjust my opinion, then I want to find a new venue.”

Bruce says she turns a profit “large enough to stay committed and to expand,” though she declined to say how many paying subscribers she has. That people pay to hear her is a testament to her perspective: She’s a gun-toting lesbian who describes herself as “a pro-choice feminist, independent conservative who strongly identifies with Tea Party patriots.”

Although starting an online radio program can cost nothing if you already own a computer, to do it right requires an investment. Two computers, broadcast software, a high-end microphone and a mixer will set you back at least $3,000, and a server can cost $100 a month. The big cost not usually considered, though, is media and personal-liability insurance; a good policy can run more than $20,000 a year.

Predating Carolla and Bruce — and almost everyone else — in online radio is Matt Alan, a longtime DJ on terrestrial radio and now a DJ on the Sirius XM ’70s channel.

During the 1990s, Alan created a radio show about cigars that aired Saturdays on regular radio, and he took it online a decade ago. Nowadays it’s called Outlaw Radio, and it’s a freewheeling discussion about politics, pop culture, cigars, booze, poker and anything else. It’s broadcast from an 1870s-style makeshift saloon built in Alan’s backyard in the San Fernando Valley that he calls the Lighten Up Lounge. Cigar and liquor brands are obvious sponsors.

Meat Loaf has gotten soused there, John Schneider snorted tequila and Alan threw Dan Haggerty’s son through a wall because he spoke inappropriately about his teenage daughter — all on live, online radio.

“We have no secrets here,” Alan said.

The eclectic guest list has included such legendary radio talent as Shadoe Stevens and Rick Dees along with celebrities from various walks of life including Peter Frampton, Lee Iacocca, Kato Kaelin and Buck Henry. Sometimes the guests will indulge a bit too much (they are in a bar, after all) and say things they wish they hadn’t said — things they’d never get away with on traditional radio.

Alan’s got 250,000 listeners for his live show each Saturday and various repeats each week, many of whom tune in via their in-car Internet connection. When that technology is widely adopted — probably inside of 10 years — “then all bets are off, and all those terrestrial radio stations are worth about a nickel,” Alan said.

Certainly, Alan, Bruce, Carolla — each in their 40s — and others online will fill some of the void left as some of today’s top talkers head for semi-retirement. Other young guns (relatively speaking) with the potential to be as big as a Schlessinger or Stern some day include:

— Andrew Wilkow: At 38, he fashions himself the “next generation of great talk radio.” Top-five talker Levin has indicated his agreement. Wilkow quit terrestrial radio four years ago to join Sirius XM.

— Mike Church: Also on Sirius XM, this 48-year-old Southern-rock conservative is sometimes mistakenly categorized a shock jock. A musician, he peppers his show with original parody songs, like “Obama,” a spoof on Toto’s “Rosanna,” and “Mr. Jefferson,” a spoof on Simon & Garfunkel’s “Mrs. Robinson.”

— Pete Dominick: The 34-year-old comedian is passionate about politics but fashions himself non-partisan (his positions are largely liberal, but don’t you dare “label” him). Dominick’s Sirius XM interview of Rick Sanchez resulted in CNN firing Sanchez.

— Bubba the Love Sponge: The 44-year-old shock jock was regularly scrutinized by the FCC while on regular radio. Today, he’s on a Sirius XM channel programmed by Stern.

— Dave Boze: This 38-year-old conservative talker worked himself up the ranks in Seattle until getting his own show. He has already proved his national chops by subbing for Medved.

— Tim Conway Jr.: Funny like his dad but more political, the 47-year-old mostly conservative host is heard in Los Angeles on KFI AM. Among his more popular regular bits is the politically incorrect “What the Hell Did Jesse Jackson Say?”

— Breitbart: This 41-year-old’s many online news sites provide fodder for talk radio, and he is a frequent sub for Savage, Dennis Miller and other national and local talkers. “If the right offer for my own show came along, I’d hug it like a teddy bear,” he told The Hollywood Reporter.

— Jim Rome: The 45-year-old sports aficionado can talk smack with the best of them, and his audience eats it up. He’s already a Top 25 host, according to Talkers, with potential to grow even more.

— Kim Komando: The 43-year-old computer expert is already in the Top 15, rare for a weekend-only show. Sometimes refering to herself as “America’s Digital Goddess,” she answers calls related to consumer electronics.

— Mancow Muller: The 44-year-old shock jock, mostly syndicated in smaller markets, had himself waterboarded on air and once blocked the Bay Bridge in the Bay Area to give a sidekick a haircut. He has become more mainstream and less slapstick over the years.