The station was launched on December 26, 1979 as DXRK by then-Mayor Pedro "Oloy" N. Roa, through his company P.N. Roa Broadcasting System. The station was then called 99.9 RK, bearing the slogan "The Rhythm of the City". Its format was more of contemporary hit radio. On December 27, 1979, 99.9 RK it had its first broadcast and it operates 24 hours a day, 7 days a week. On February 3, 1997, 99.9 RK limited its broadcast from 8:00 AM to 12:00 MN. 99.9 RK ceased broadcasting on December 31, 2002 after 23 years of broadcasting.
Acquired back then by Baycomms Broadcasting Corporation, DXRK changed its callsign to DXBD and began its test broadcast on January 27, 2003. On February 24, 2003, it was relaunched as 99.9 Bay Radio Cagayan de Oro. The station signed on at 5:00 AM. The format of the station was mass-based. It initially operates from 5:00 AM to 12:00 MN. At that time, its studios and transmitter were located at J.R. Borja St. In 2008, its callsign was reverted to its original callsign, DXRK. From March 2, 2009 to March 28, 2010, Bay Radio began broadcasting 24 hours a day except on Mondays where it signs off at 12:00 MN to 5:00 AM. From April 5 to December 18, 2010, Bay Radio began broadcasting 24 hours a day, 7 days a week. After 7 years of broadcasting, 99.9 Bay Radio signed off for the last time on December 25, 2010 in Christmas Day with the last program of Foreign Saturday Nights and the last song "Already Gone" by Kelly Clarkson. Since the next day, 99.9 FM was left dormant. During that time, the station was sold to Hypersonic Broadcasting Center, and its studios moved to its present location at 2nd floor, SBS Building, C.M. Recto Ave. and transmitter moved to its present location at Osmeña St.
Magnum Radio era: 2011–present
On February 1, 2011, after being on hiatus for more than a month, 99.9 FM returned on air as a test broadcast. On February 28, 2011, 99.9 FM was relaunched as Magnum Radio and changed its call letters to DXMR. It initially operated daily from 4:00 AM to 12:00 MN. Under the new management, the station flipped its format to a hybrid of news/talk and music, similar to 89.5 Brigada News FM General Santos. On October 1, 2012, Magnum Radio began broadcasting 24 hours a day, except on Mondays where it signs off at 12:00 MN to 4:00 AM. Since the 2011 relaunch, Magnum Radio has been ranked as the overall #1 FM station in Cagayan de Oro, according to the KBP-Radio Research Council Kantar Media Radio Surveys.
