On its first day as owner of CBS Radio, Entercom Communications has blown up classic hits WJMK FM 104.3, replacing the six-year-old K-Hits brand with a new format of classic hip-hop and R&B.

At 11 a.m. Friday the company launched “The New 104.3 JAMS – Chicago’s #1 for Throwbacks,” geared to an ethnically diverse audience of millennials with rhythmic music of the ’90s and early ’00s. Core artists include Jay Z, Mary J. Blige, Notorious B.I.G., TLC, 2pac, Nelly, Beyoncé and Destiny’s Child, Eminem, Aaliyah, Fugees, and Kanye West.

The station will air initially without commercials or announcers. In the coming weeks it’s expected to change call letters to WBMX, evoking the legendary urban contemporary station that aired in Chicago from 1973 to 1988. (The call letters currently are being used by an Entercom station in Boston.)

”The expertise and energy that Entercom brings into Chicago coupled with our all-star programmers will bring incredible new life to this storied frequency,” said Jimmy deCastro, new senior vice president and market manager of Entercom Chicago. “We will be dancing in the hallways with you, Chicago.”

Greg Solk continues as operations manager and program director of WJMK as well as adult album alternative WXRT FM 93.1.

The sudden demise of K-Hits will cost the jobs of morning host Dave Fogel, midday host Brian Peck (who was hired only two weeks ago), afternoon host Jeffrey T. Mason and assistant program director Bob Lawson, in addition to a number of part-time staffers. A new lineup of on-air personalities will be unveiled in January.

In the latest Nielsen Audio survey, WJMK tied for 18th place with a 2.4 percent audience share. At its peak in August 2015, it ranked fourth with a 4.1 share.

But the format change has more to do with revenue than ratings, insiders said. By positioning 104.3 JAMS between iHeartRadio’s two urban powerhouses — the older skewing WVAZ FM 102.7 and the younger skewing WGCI FM 107.5 — Entercom hopes to capture a share of iHeart’s estimated $40 million in combined revenue. It also may cut into Crawford Broadcasting’s WSRB FM 106.3 and WPWX FM 92.3, among other stations.

Immediate beneficiaries appear to be Cumulus Media’s classic hits WLS FM 94.7 and Weigel Broadcasting’s soft rock/oldies 87.7 Me-TV FM, which just lost a direct competitor.

Targeting listeners between 25 and 54, 104.3 JAMS will be backed by an aggressive marketing campaign, including digital and social media, according to Entercom.

“The New JAMS will have a playlist that appeals to ethnically diverse millennials with a 35-44 sweet spot, centered musically in hip hop’s breakout era in the mid to late ’90s,” Entercom told advertisers Friday. “The Throwbacks format has been instantly successful in markets where hip-hop and R&B was hugely successful in the ’90s and early ’00s, and we believe that we will have that same success in Chicago.”

K-Hits debuted here in 2011 as WJMK’s replacement for the ill-fated Jack FM variety format. “K-Hits was one of five different radio stations playing some form of classic rock, classic hits or oldies,” the company acknowledged. “Chicago still loves ’70s and ’80s music, but between The Loop, The Drive, WLS FM, and Me-TV FM, there are a lot of places to hear ‘Don’t Stop Believin”,’ ‘Old Time Rock And Roll’ or ‘Take On Me’ and not a lot of listener loyalty to any one station.”

As expected, Entercom closed Friday on its $1.7 billion merger with CBS Radio, forming the nation’s second largest radio company with 244 stations in 47 markets (including 23 of the top 25). Along with its format change in Chicago, Entercom also flipped stations in New York and Dallas to alternative rock.

In Chicago, Entercom owns WJMK and WXRT as well as all-news WBBM AM 780/WCFS FM 105.9, sports/talk WSCR AM 670, Top 40 WBBM FM 96.3, and country WUSN FM 99.5.