|City of license||St. Louis Park, Minnesota|
|Broadcast area||Minneapolis-St. Paul|
|Branding||104.1 Jack FM|
|Slogan||"Playing What We Want"|
104.1 HD-2 Adult contemporary
|First air date||1962 (as KRSI-FM)|
|Format||Commercial; Adult Hits|
|Callsign meaning||K Z JacK|
|Former callsigns||KRSI-FM (1962-1973)
|Sister stations||KMNB, WCCO
part of CBS Corp. cluster with TV station WCCO-TV
KZJK (104.1 FM) is a radio station broadcasting the adult hits "Jack FM" format in the Minneapolis-St. Paul region of Minnesota. The station is owned by CBS Corporation through the radio subsidiary CBS Radio.
Currently, the station's main transmitter is rated at 89,000 watts effective radiated power and is located on KMSP-TV's tower in the suburb of Shoreview, with the city of license in the suburb of St. Louis Park. An auxiliary transmission facility is located atop the IDS Center in downtown Minneapolis.
The 104.1 MHz frequency in the Twin Cities area signed on in 1962. For much of its early history, the station was KRSI-FM, paired with a sister AM station with the same call letters. The two stations simulcast with each other on and off through much of their existence, and finally separated when the AM station was sold separately in 2005.
Until the mid-1990s, the station was hampered by a badly located tower. Although they were licensed to the west Minneapolis suburb of St. Louis Park, the tower was located far east of the Twin Cities, in Somerset, Wisconsin. The result was a spotty signal in parts of the metropolitan area, and it would be many years until this situation was rectified.
Partly due to signal limitations and impatient management, the 104.1 FM frequency went through many format changes throughout its history.
KRSI-FM to KFMX and back 
From February 1968 until 1973, KRSI-FM played Top 40 hits and oldies as "Request Radio", simulcasting with their AM sister station. This was by far the most successful format for both stations, and in Spring 1969, they were the #3 station in the market, behind WCCO and WDGY.
The two stations moved away from oldies and more toward current pop music in 1971. In March 1973 950 AM became the first affiliate of Drake-Chenault’s automated “Great American Country” format, as both stations moved from their location in St. Louis Park to new facilities in Eden Prairie (which today is still home to 950 AM). The FM station broadcast in stereo for the first time and continued with a rock/Top 40 hybrid format, soon changing its call letters to KFMX.
KFMX FM went through a succession of different formats and transitions throughout the rest of the decade. For a brief time, they played freeform rock, going up against KQRS-FM. They began playing disco music at night in 1978, soon adopting the format full-time and becoming "Disco 104". By this time, the AM station was playing rock/Top 40 as "Musicradio I-95" (featuring a great deal of New Wave music). KFMX gave up disco in February 1980 as the fad faded in popularity, and both stations switched to an adult standards/"Music of Your Life" simulcast, with KFMX becoming KRSI-FM once again.
In 1981, the FM station switched to country music, as "K-JO Country", adopting the KJJO call letters. They were up against much competition from market leader WDGY, low-rated KTCR and soon, KEEY. KJJO was never very competitive as a country station. In September 1983, after playing "Old Time Rock and Roll" by Bob Seger for 48 hours straight, they launched a new format, "Twenty Years of Rock and Roll" as classic hits "K-JO 104".
KJJO's ratings improved with their classic hits format, but the station was still was not making much of an impact in the market. In 1986, KJJO transformed yet again and introduced a hard rock format, to go head-to-head with the classic rock-leaning KQRS-FM. They kept the KJJO call letters, and dubbed themselves "Hot Rockin' 104" (later "Rock 104"). At its peak, the hard rock format pushed KJJO into the top 10 in the local Arbitron ratings. KJJO was not very consistent with the harder format, though, as they went back and forth between heavy metal and mainstream album-oriented rock. In 1987 they picked up the syndicated heavy metal Z-Rock radio network affiliation for their AM sister station.
Modern Rock KJ104 
By 1990, as heavy metal started to fade in popularity, KJJO, by now a mainstream rock station, began adding more alternative rock songs to the playlist. Eventually, KJJO ditched the heavy metal and mainstream rock altogether and became a full-fledged modern rock station. At first, they called themselves "104FM", but eventually picked up the moniker "KJ104".
During the station's modern rock run, the playlist became more and more adventurous. Over time, KJ104 garnered a lot of positive word of mouth in the Twin Cities area, though ratings were still mediocre. The station's manager complained in the local media that KJ104's listeners were not filling out the Arbitron ratings diaries, the results of which are used to measure a radio station's success.
Back to country as "Thunder 104.1" 
In the summer of 1992, KJJO publicly announced a pending switch back to country music, which was becoming very popular around the time, amid a large outcry from KJ104's dedicated fans. At 6 AM on September 8, after signing off the modern rock format by playing "It's the End of the World as We Know It (And I Feel Fine)" by R.E.M., "Thunder 104.1" debuted. As a country station, ratings went up slightly, but they could not compete with the established K102 and the soon-to-sign-on WBOB (BOB 100).
The two other country stations trounced Thunder 104.1, soon knocking them back down to the same level as the former KJ104. To set themselves apart from the heavy competition, they evolved into a classic country format, and ratings slightly improved. Meanwhile, several former KJ104 employees were working at bringing the much-missed modern rock format back to the local airwaves, which culminated with the debut of REV 105 in April 1994. A month prior to this, hard rocker KRXX (93.7 FM) became KEGE ("The Edge") and soon became the highest-rated modern rock station in the country, succeeding where KJJO, as KJ104, failed.
Station sold, more format changes 
The country fad died down by the mid-1990s, and with K102 and BOB 100 firmly establishing themselves, KJJO bowed out of the format and flipped to smooth jazz in April 1995, with the KJJO call letters finally retired and new calls KMJZ introduced. During this time, ownership transferred several times. Nationwide Communications bought both the AM and FM stations from the estate of its longtime owner Roy Park, then Nationwide was bought by Jacor, which spun the station off to Infinity Broadcasting (which later became part of CBS Radio).
In October 1998, the station changed format once again, to Modern AC as "104.1 The Point" with the WXPT call letters. They evolved into an '80s hits format by November 2000, and the station took the "Mix 104.1" moniker. While never a dominant station, Mix 104.1 was a modest ratings and financial success, as the station's transmitter woes were finally resolved by the move to KMSP-TV's antenna array in Shoreview, Minnesota, home to the transmission facilities of most of the area's big FM stations.
Jack FM 
On May 10, 2005, three weeks after the format change, the call letters were officially changed to KZJK.
104.1 Jack FM has a much bigger playlist than most radio stations. While many stations commonly have 200-400 songs in rotation, the Jack format is known for playlists with roughly 1,200 songs, reducing repetition.
The "Jack FM" "Happy Ending" Event at 5 PM on January 12, 2009 was announced frequently on the station over the few days leading up to the event. The last song played before the event was "The Last Song" by Edward Bear, a nod to both the "end" of Jack and the rumored name of the new station, The Bear.
The "Happy Ending" culminated as a promotional gimmick to advertise for Jack FM's hour-long commercial-free hour to air each weekday starting at about 5 PM Central Time.
It is also noted that unlike most adult hit stations that only play recurrents and recent oldies mixed in with classic hits, this station plays at least one current hit an hour to better compete with more current based competiters KTWN-FM and KDWB.
HD2 Station 
KZJK offered an HD2 subchannel that used to air a smooth jazz format, somewhat of a revival of the old KMJZ. Smooth jazz was also on 100.3 FM for several years as KJZI, prior to the station switching to talk as KTLK-FM in late 2005.
Due to the demise of sister station "102.9 Lite FM" on December 26, 2011, 104.1 HD2 flipped to adult contemporary on that same day, as Lite FM flipped to country music. 102.9 instead flipped on December 25 at 6:00 p.m., about 14 hours earlier than originally planned. The switch from smooth jazz to "Lite FM" also occurred at this time.
- 104.1 Jack FM KZJK official website
- Query the FCC's FM station database for KZJK
- Radio-Locator information on KZJK
- Query Arbitron's FM station database for KZJK
- Radiotapes.com Featuring historic airchecks of various formats heard in the past on 104.1 FM including KFMX-FM Disco, KJJO-FM, KRSI-FM along with other Twin Cities radio station airchecks dating back to 1924
- Rick Burnett's TwinCitiesRadioAirchecks.com More historical recording of 104.1 FM including KRSI and KFMX, and other Twin Cities radio stations.