Balancing on a giant rubber ball in a broadcast studio and control room carved out of a cottage in Petaluma, Calif., Leo Laporte is an unlikely media mogul.

From that little town in California wine country, he runs his empire, a podcasting network, TWIT. For 30 hours each week, he and the other hosts on his network talk about technology — topics like the best e-book reader or how to get rid of a computer virus — for shows that he gives away online.

Nerdy, yes. Silly, no. TWIT gets its name from Laporte’s flagship podcast, “This Week in Tech,” which is downloaded by a quarter of a million people each week. He produces 22 other technology-focused podcasts that are downloaded 5 million times a month. He also streams video all day long that captures his podcasting and a weekend radio show on computers, “The Tech Guy,” that reaches 500,000 more people through 140 stations.

“I don’t want to be just a carbon copy of existing media,” said Laporte, who at 54 is just old enough to remember using carbon paper in typewriters to make duplicates.

Advertisers, especially technology companies, appreciate Laporte’s reach. Mark McCrery, chief executive of Podtrac, which is based in Washington, and measures podcast audiences and sells advertising, said TWIT’s advertising revenue doubled in each of the last two years and was expected to total $4 million to $5 million for 2010.

Starting at $40 per thousand listeners, TWIT’s ad rates are among the highest in American podcasting and are considerably higher than commercial broadcasting rates, which are typically $5 to $15 per thousand listeners.

Podcasting is an often overlooked corner of the media world. The term is derived from iPod, the Apple media player that can be used to listen to these radio-like programs as well as recorded music. The iTunes store from Apple, where about 75 percent of the audience for podcasts looks for fresh material, contains about 150,000 regular shows featuring has-been and up-and-coming comics and sex talk, as well as mainstream fare like NPR and CNN broadcasts. Edison Research estimates that a quarter of all Americans over the age of 12 have listened to or watched at least one. There are also video podcasts.

Laporte has shown there is a lot of life in podcasting. Doug Keith, president of Future Research Consulting in Philadelphia, which tracks media companies and publishers, said advertisers were drawn to the network because tech enthusiasts were keen on its content.

In July, Laporte spent three hours signing hundreds of autographs for members of the so-called TWIT army in Detroit. Some of his fans had him sign their iPads. No wonder then, that $20,000 a month in voluntary contributions comes in from the TWIT website, which has a series of “Tip Leo” buttons that set off recurring monthly contributions of $2, $5 and $10.

Laporte’s first great love was radio. In the late 1970s, he dropped out of Yale to pursue a radio career. He began talking about technology on the radio in 1990. In the dot-com boom of the late 1990s, he appeared on tech-focused television programs, including as an animated character on “The Site,” an MSNBC show devoted to the nascent Internet. Laporte played an espresso barista named Dev Null and wore a motion-capture suit to animate the character he voiced.

Many who listen to or watch his podcasts today remember him from such cable TV shows as “The Screen Savers” and “Call for Help.” And it was a round-table discussion by former staff members from “Screen Savers” that prompted Laporte to begin “This Week in Tech” in 2005. Laporte posted a recording of the discussion at a Macworld conference on his blog, not intending it to become a podcast. But it got so many hits, he started posting regularly.

Laporte, now with a full head of graying hair, has an encyclopedic command of digital technology, and he keeps the show, which consistently reaches the top 200 podcasts list at iTunes, lively with his ability to mimic voices and accents. He frequently does impressions of sitcom and cartoon characters to make a point about network-attached storage devices or bit rates.

“This Week in Tech,” a two-hour show, features journalists and industry insiders talking shop. Some who live in Silicon Valley or San Francisco drive up to Laporte’s cottage to join him for the Sunday afternoon recordings. Other far-flung participants connect through Skype. A contraption in the TWIT control room known as the Skyposaurus employs four computers to connect Skype video callers.

In the studio, Laporte’s eyes dart from one computer screen scrolling mile-a-minute chat-room banter to another where he searches Google for answers for guests and listeners, while mixing sound, switching video signals and moderating panel discussions.

But it is the hundreds of hard-core tech fans in the show’s chat rooms that make the podcasts work. They serve as Laporte’s researchers, fact checkers and Greek chorus.

“If an error is made, the chat room will be all over it,” said John Dvorak, a columnist for PC Magazine and a regular on “This Week in Tech.” “This is real-time fact checking. There’s nothing like it.”

During recordings of “This Week in Tech,” as many as 1,500 people are in chat rooms typing away at a furious pace.

Next year, the TWIT empire is expected to move into a larger building down the street from its current headquarters. Laporte plans to start a morning show this spring to compete with drive-time radio broadcasters.

“It’s not as if I had a plan for all this,” Laporte said. “It just kind of happened. It was almost as if we had this audience that was waiting for the medium to come along.”