|City||Los Angeles, California|
|Broadcast area||Greater Los Angeles Area|
|Frequency||93.1 MHz (HD Radio)|
|Branding||93.1 Jack FM|
|Slogan||Playing What We Want|
|Subchannels||HD2: KFRG simulcast "93.1 HD2 K-FROG" (Country)|
HD3: CBS Sports Radio
(Entercom License, LLC)
|KAMP-FM, KFRG, KNX, KROQ-FM, KRTH, KTWV, KXFG|
First air date
|March 30, 1948 (as KNX-FM)|
Former call signs
|KNX-FM (1948-1983 and 1986-1989)|
Call sign meaning
|K Columbia Broadcasting System (former legal name of CBS, the station's former owner)|
|HAAT||1,074 meters (3,524 ft)|
KCBS-FM (93.1 FM, "Jack FM") is a radio station in Los Angeles, California, serving Greater Los Angeles on 93.1 MHz and owned by Entercom. KCBS-FM airs an adult hits music format branded as "93.1 Jack FM".
Unlike other radio stations airing the Jack FM format, KCBS-FM runs a fairly focused playlist of popular classic rock and alternative rock tracks. Currently, the station has no air staff except for Crystal Z with her "Jacktivities" (events and whatever announcements deemed worthy by "Jack") and Howard Cogan supplying prerecorded quips and remarks between songs. Unlike most other stations in this format, the call sign does not include any form of the word "Jack," opting instead to hold over the call letters from a previous format, including the station's former corporate identity. This is similar to its sister station in New York City, which maintained its WCBS-FM call letters during its two-year run as "Jack FM" from 2005 to 2007.
Although Jack proclaims that the station is run "in a dumpy little building in Culver City", studios and offices for KCBS-FM are actually at the intersection of Venice Boulevard and Fairfax Avenue in Los Angeles, about half a mile north of Culver City. The station's transmitter is based on Mount Wilson.
On March 30, 1948, the station signed on as KNX-FM. KNX-FM was a simulcast of its AM sister station KNX until the mid-1960s. The station, along with other CBS-owned FM radio stations, aired a beautiful music format branded as "The Young Sound".
In 1971, KNX-FM switched to a mellow rock music format, featuring artists heard on other rock stations but choosing softer selections than heard on rivals KLOS and KMET. (A group of volunteers launched an internet stream recreating the KNX format of the 1971-1983 era in 2019.) 
On August 25, 1983, KNX-FM adopted a Top 40 music format, similar to the other CBS Radio FM stations - and branded as "Hitradio 93 KKHR". The heritage KNX-FM call sign was switched to KKHR. KKHR was not a traditional Top 40 music format of the time as the playlist was more stringently limited to 30 songs. The original KKHR disc jockey staff consisted of Lou Simon, Dave Donovan (whose real name is Joe Cipriano), Chris Lance, Todd Parker (replaced by Jack Armstrong several months later), and Mark Hanson.
In 1986, the Top 40 format ran its course on 93.1 due to its lackluster ratings. The mellow rock music format and heritage KNX-FM call letters were returned under the new branding "Quality Rock".
KNX-FM struggled with low listener ratings, and wasn't able to re-capture its original audience. On March 2, 1989, at 12:00 p.m., following a day-long stunt with a ticking clock during songs and an announcement from vice president and general manager Charlie Seraphin, an oldies music format was introduced and the heritage KNX-FM callsign was dropped yet again, this time in favor of KODJ to complement the change in branding to "Oldies 93.1". KODJ competed with crosstown rival KRTH, which later came under common CBS Radio ownership when ownership limits were relaxed by the FCC. KODJ focused more on the 1950s and the early 1960s era of oldies music than rival KRTH. DJs on KODJ were The Real Don Steele, Charlie Tuna, Rich Fields, Machine Gun Kelly and Jeff Serr. In response to KODJ's debut, KRTH gradually reduced and eventually faded out the amount of newer songs from its playlist, focused mainly on the 1960s decade of oldies with a selected number of top songs from the late 1950s. In addition, KRTH brought in Bill Drake as consultant while featuring all new jingles by the Johnny Mann Singers, which helped it reach higher ratings. The Real Don Steele left KCBS-FM in mid-1992 to join KRTH. Charlie Tuna the morning host at KODJ/KCBS-FM from 1989-1993 would later work at KRTH from 2008-2014.
On July 12, 1991, at 2 p.m., KODJ changed to its present callsign, KCBS-FM as part of an re-imaging marking campaign to bring in new listeners believing the "CBS-FM" call letters had a more stronger association with the oldies format. These call letters had previously been used by two CBS-affiliated stations (now KSOL and KLLC) in San Francisco. KCBS-FM still kept the oldies format, but shifted its focus mainly to the 1960s decade of oldies with a lesser selection of 1950s oldies, and more early 1970's rock oldies to better compete with KRTH. Due to continued low ratings and KRTH holding the majority share of the oldies market, on September 10, 1993, at 3 p.m., KCBS-FM flipped to a classic rock/classic hits format, and branded itself as "Arrow 93FM, All Rock and Roll Oldies". "Arrow" focused its new oldies format on the late 1960s and the entire 1970s decade with an emphasis on only classic rock oldies that did not include pop, bubble gum, disco, or doo-wop music. The listener Arbitron ratings for KCBS-FM went from 18th to 3rd place by the end of 1993, making the new format an immediate success. The station kept the KCBS-FM call letters, but would only quickly identify its call sign once at the top of the hour per FCC station identification requirements. The format would later evolve towards classic rock of the late 1960s, 1970s, and early 1980s, and re-branded itself as "Arrow 93FM, All Rock & Roll Classics" in 1996.
Infinity Broadcasting (as CBS Radio was known at the time) won the licensing rights to brand its adult hits music formatted radio stations as "Jack FM". Many Infinity/CBS Radio stations adopted the adult hits format and "Jack-FM" branding which led to yet another format change for KCBS-FM. On March 17, 2005 (St. Patrick's Day), after an all-day stunt with music from U2 (as that band is from Ireland), the classic rock format was dropped in favor of adult hits, branded as "93-1 Jack-FM". The Jack format was a break from the heavily niched formats that had developed beginning in the 1970s. Jack was also unusual in that it employed no DJs, and had a much larger playlist than the typical classic hits or classic rock radio station.
The Los Angeles incarnation of Jack includes more modern rock titles than most Jack outlets, reflecting the local influence of KROQ during its alternative heyday. The station debuted with a blend of pop and rock from the late 1960s to late 1980s, with a sprinkling of newer, sometimes almost current, tunes. Eventually, the newer songs and pop songs were phased out in favor of mostly classic rock and classic alternative. KCBS-FM is the longest-serving of all of CBS' Jack stations.
Though the station has no DJs, KCBS-FM will occasionally respond to current events, such as playing all Michael Jackson songs following his death, or spinning a celebratory tune or two following a local sports victory.
The "voice" of Jack FM is a real person named Howard Cogan. His quips which are heard between songs are created by a team of writers. As Jack became popular, Cogan moved to Los Angeles to record his comments more easily. He is also the voice-over artist for other "Jack FM" stations around the country.
In October 2008, CBS Radio chose not to move the KCBS-FM call letters to its sister station 106.9 in San Francisco, after that station flipped from classic hits to an all-news simulcast of 740 KCBS. That station remains KFRC-FM, heritage calls in themselves.
On February 2, 2017, CBS Radio announced it would merge with Entercom. The merger was approved on November 9, 2017, and was consummated on the 17th. As part of the merger, the FM radio rights to the Los Angeles Rams of the National Football League were moved to KCBS from KSWD, which was sold off as part of the deal when it flipped to Contemporary Christian format as KKLQ on November 16, 2017.
In addition to the main Jack FM format on HD1, 93.1 HD-2 broadcasts CBS Sports Radio. Before KLSX switched from Talk to CHR in 2009, 93.1 HD2 carried a CHR format with the "AMP Radio" branding. Former sister station KFWB had been broadcasting on the KCBS-FM HD3 signal, but due to that station's sale, its signal is no longer heard on KCBS-FM. As of January 6, 2018, that signal began simulcasting KNX (AM), which moved over from KAMP. It has since carried KFRG/KXFG.