At 5 p.m. Oct. 9, after the final notes of "Streetcorner Symphony" by Rob Thomas, the voice of Mike Missanelli came up on music station WNUW-FM (97.5).

The station, he proclaimed, was now "97.5 the Fanatic." Greater Media had decided to drop its underperforming adult-contemporary format known as Now 97.5 and instead simulcast on FM most of the programming from its similarly low-rated AM sports-talk station, 950 ESPN.

FM sports talk had arrived, a first in Philadelphia.

The format, with its crisp, clear FM sound, is lucrative because of its appeal to young and middle-aged men. Sports talk has been migrating in recent years to the FM band, especially in rabid sports towns.

From early reports, Greater Media's entry showed immediate ratings muscle, in addition to saving the cost of programming one of the stations.

In its first full ratings month, Arbitron ranked WPEN-FM seventh among its target of men ages 18 to 49, with an estimated weekly audience of 231,700. By comparison, the AM station was 11th with an audience of about 131,000 in September, its last full month with sports talk before the FM sign-on.

Few Philadelphia radio topics engender as much public debate as sports talk, so the question quickly arose: Does CBS-owned WIP-AM (610) - it has had a lock on sports talk in town for 20 years and is home to Angelo Cataldi, Glen Macnow, Anthony Gargano, and Howard Eskin - have anything to worry about with the new WPEN-FM (97.5)?

Andy Bloom, operations manager at WIP, says, "We don't even notice that they're there. It's like comparing the Reading Phillies with the Philadelphia Phillies."

WIP trumpeted its No. 1 finish among its own target, the slightly older group of men ages 25 to 54, for the fourth consecutive month.

And Cataldi, who is believed to be about to re-sign with WIP, typically draws more than triple the audience that the Fanatic does with ESPN's syndicated Mike & Mike show.

Still, the Greater Media stations are racking up impressive numbers later in the day.

The rise of the Fanatic has been driven largely by Missanelli, whose program from 2 to 7 p.m. was third in the time period in November among men 18 to 49 - and first if the AM and FM ratings are combined.

It was Missanelli's ratings on AM, especially among young men, that drove the decision to add the FM station, said Matt Nahigian, the WPEN program director.

For Missanelli, the competition with WIP seems personal. He had two tours of duty with WIP, including three years cohosting with Eskin, now his rival in afternoon drive time.

"WIP is a habit that takes a long time to break," said Missanelli, who was fired from WIP in 2006 over an altercation with a producer.

Missanelli started at 950 ESPN on April 1, 2008, with the stated goal of beating Eskin in the ratings. Paired now with Jon Marks, he first did that in April 2009.

"My show went to No. 1 after a year while battling a show that had a 20-year head start," Missanelli said.

Eskin's take: "What kind of music does 97.5 play?" he said, declining to engage or even mention Missanelli. "Seriously, WIP is the sports-talk leader in Philadelphia. We just focus on what we do to create exciting radio for our listeners."

Eskin's show, with Ike Reese as microphone mate of late, has been on a ratings rise of its own since May.

Radio analyst Joe Lenski says that rather than cannibalize WIP's audience, the Fanatic will draw much of its audience from FM listeners, not AM listeners.

Lenski, vice president of Edison Research in Somerville, N.J., used the analogy of stores in a mall. "It's as if they've opened a new store where other people are shopping," he said.

The Fanatic is getting younger listeners - "especially men who won't turn to the AM band," said Lenski. He based his assessment on a similar sign-on in Boston in the summer. "AM, what's that?" younger males told him in his research.

Lenski said that if he were programming WIP, he would be worried about the emergence of a competitor, but "but I wouldn't be desperate thinking that all my listeners are going to cross the street. But WIP is a longtime heritage station"; it broadcasts Flyers and 76ers games and has access to the Phillies and Eagles.

Despite Bloom's blasé confidence - and his dismissiveness about the Fanatic's FM sign-on - his company has been at the fore of the sports-talk-to-FM movement. Last year, CBS added the format to WXYT in Detroit and KRLD-FM in Dallas, and this summer flipped WBZ in Boston and WJFK in Washington.

Don't expect CBS executives in Philadelphia to put WIP on FM. They have firmly maintained that they would not change the formats of their FM music stations WYSP (94.1) and WOGL (98.1). CBS also owns news KYW-AM (1060) and talk WPHT-AM (1210).

For WPEN program director Nahigian, the decision to add FM was bittersweet. His wife, Joey Fortman, was among those laid off from her WNUW job that Friday afternoon when the station went to sports talk.

Greater Media, a privately held company, also owns WMMR (93.3), WBEN (95.7), and WMGK (102.9), all of which compete with CBS's WYSP.

The AM station at 950 had been through a series of formats (oldies, standards, oldies again) before settling on sports talk in August 2005. Greater Media acquired the 97.5 frequency in 2006, and saw middling ratings with every format: smooth jazz, light rock, and most recently adult contemporary.

The AM/FM dualcast gives Nahigian more options. "I can have Villanova basketball on AM, and on the FM I can have an all-Eagles show," he said.

The town seems big enough for more than one sports-talk station.

"In a market that is so sports-obsessed and blessed with interesting pro teams, both stations will be viable," said Tom Taylor, a respected trade observer with Radio-Info.com. "There will be partisans of each, and people who enjoy both."

Contact staff writer Michael Klein at 215-854-5514 or mklein@phillynews.com.