Unlike other radio stations of similar format, the Los Angeles Jack FM playlist runs a fairly focused playlist of popular classic rock and Alternative Rock tracks. Currently, the station has no air staff save for Tami Heide with her "Jacktivities" (events and whatever announcements deemed worthy by "jack"). Unlike most other stations in this format, the call sign no longer includes any form of the word "Jack," opting instead to hold over calls from a previous format. This is similar to its FM sister station in New York, WCBS-FM, which had maintained its WCBS calls during its run as "Jack FM."
Although Jack proclaims that the station is run "in a dumpy little building in beautiful downtown Culver City", KCBS-FM is actually at the intersection of Venice Boulevard and Fairfax Avenue in Los Angeles, about ½ mile north of Culver City. The station's transmitter is based on Mount Wilson.
The station signed on March 30, 1948, as KNX-FM. KNX-FM was a simulcast of sister station KNX until the mid-1960s. The radio station, along with other CBS-owned FM radio stations aired a beautiful music format branded as "The Young Sound".
On August 25, 1983, long after other CBS-owned radio stations moved on to other formats, KNX-FM adopted a Top 40 music format - again similar to the other CBS Radio stations branded as "Hitradio 93 KKHR". A change of the heritage KNX-FM call letters followed to KKHR. KKHR was not a traditional Top 40 music format of the time as the playlist was more stringent 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 likely due to its lackluster ratings caused by listeners migrating to KOST-FM to get their mellow music fix. 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 PM, following a day-long stunt with a ticking clock during songs and an announcement from vice president/GM of KNX-FM, Charlie Seraphin, an oldies music format was introduced and the heritage KNX-FM call letters were dropped yet again 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. DJ's on KODJ were The Real Don Steele, Charlie Tuna, Rich Fields, and Machine Gun Kelly. In response to KODJ's debut, KRTH gradually reduced and eventually faded out the amount of newer songs from the playlist, focused mainly on the 1960s decade of oldies with only a selected number of top songs from the late 1950s, and brought in Bill Drake as consultant while featuring all new jingles by the Johnny Mann Singers thus receiving 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 call letters, KCBS-FM as part of an re-imaging marking campaign to bring in both more and 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 1950's 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 classic hits, and branded itself as "Arrow 93FM, All Rock and Roll Oldies". Arrow 93FM focused its new oldies format on the late 1960s and the entire 1970's 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. Arrow 93FM kept the KCBS-FM call letters, but would only quickly identify its call letters once at the top of the hour per FCC station identification requirements. The format would later evolve towards classic rock of the late 1960s, 1970's, and early 1980's 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 their 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 hits format was dropped in favor of its present music format 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 played 70's and 80's hits from pop, rock, and alternative genres, despite the fact that these were usually not played on the same station at the time they were originally hits. Jack was also unusual in that it eschewed DJs, and had a much larger playlist than the typical "oldies" or classic rock radio station.
The Los Angeles incarnation of Jack includes much more modern rock 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 60s to late 80s, 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. It is also the longest-serving of all of CBS' Jack stations.
Though the station has no DJs and is automated, they will occasionally respond to current events, such as playing all Michael Jackson following his death, or spinning a celebratory tune or two following a local sports victory.
The "voice" of Jack FM is indeed a real person named Howard Cogan. His quips that air 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 voiceover artist for other "Jack FM" stations around the country.
In addition to the main Jack FM format on HD-1, 93.1 HD-2 broadcasts CBS Sports Radio. Former sister station KFWB (980) was broadcasting on its HD-3 signal, but due to that station's divestiture to a trust under the name Clark Radio, LLC, that signal is no longer available.