The station was launched on July 26, 1946 by Sarnia Broadcasting. In 1947, Sarnia Broadcasting Co. was granted a licence to operate an FM station at 97.5 MHz, which left the air sometime between 1948 and 1953 after being damaged from the Sarnia tornado. That station was never rebuilt. It was acquired by IWC Communications, a corporate precursor of Standard Broadcasting, in 1970, and went through a variety of sales to local owners until being acquired by its current owner, Blackburn Radio, in 1998. Blackburn also owns both of the city's other commercial radio stations, CFGX-FM and CHKS-FM.
CHOK-1-FM
In April 2007, CHOK AM applied to add an FM transmitter at Sarnia to broadcast at 103.3 MHz and simulcast the programming of CHOK 1070 AM, due to AM reception problems from metal and steel associated with the operations from petrochemical plants. Another company, Points Eagle Radio, had applied at the same time to use the 103.3 MHz frequency to broadcast Aboriginal programing. Points Eagle Radio was given approval by the CRTC to use the 103.3 FM frequency on August 7, 2007. On July 20, 2007 CHOK was given approval in part to broadcast at 100.9 MHz. On October 10, 2007 Blackburn Radio applied to use the frequency 103.9 MHz instead. On January 18, 2008 CHOK was given approval to use the 103.9 frequency with 200 watts power. CHOK began testing of its 103.9 FM transmitter atop the Kenwick Building in downtown Sarnia, on June 18, 2008. On the morning of July 23, 2008, CHOK signed on as Country 103.9 FM and would continue to simulcast its signal on 1070 AM. The station also has a low-power license-exempt repeater on 101.5 FM at the Sarnia Sports and Entertainment Centre. The 101.5 FM frequency is reserved for use by the CBC, should they choose to broadcast on that frequency in the future.
Format
On January 12, 2007 at 6AM, CHOK changed its format from news/talk and oldies, with the brand name Information Radio, to a country music format aimed at WSAQ's Canadian audience. On May 21, 2013, CHOK dropped its country format and changed its music to a gold-based adult contemporary music, with some country and classic hits mixed in. The service elements of the previous format remain in place, with hourly news reports and local talk programs. The music leans older and softer than the hot mainstream AC format of sister station CFGX-FM. Toronto Blue Jays games, which had been off the air since 2006, returned to the station, as did the Sarnia Sting. The format change came as WHLS in Port Huron updated its format from oldies to a classic hits mix. WHLS would later flip to alternative rock in 2015 as Rock 105.5, leaving CHOK the only remaining station in the market that still plays pre-1980s hits, as WGRT, WBTI and sister CFGX-FM have more modern AC formats. On December 26, 2019, CHOK dropped its gold-based adult contemporary format and changed its music back to country.
