KOST (103.5 FM) is a commercial radio station in Los Angeles, California. Owned by iHeartMedia, it broadcasts an adult contemporary radio format, switching to Christmas music for much of November and December. Its studios are co-located with its sister stations on West Olive Avenue in Burbank. KOST is the home of Ellen K, segments of whose morning show are syndicated to other iHeart AC stations on Saturday mornings. The transmitter is atop Mount Wilson alongside most L.A. based television and FM radio stations. Those FM stations, along with KOST, are considered "superpower" grandfathered stations, since their effective radiated power (ERP) greatly exceeds the level set by the Federal Communications Commission for Class B FM stations at their height on Mount Wilson. KOST broadcasts using HD Radio technology. The HD2 digital subchannel rebroadcasts co-owned talk radio station KFI 640 AM. The HD3 subchannel formerly carried the iHeart soft adult contemporary format, "The Breeze." The HD3 subchannel has since been turned off. History Early years On October 9, 1957, the station first signed on as KGLA. Noted radio programmer Gordon McLendon bought KGLA in the 1960s, changing the call letters in November 1966 to KADS. McLendon, with permission from the Federal Communications Commission, experimented with an all-advertisement format, hence the call sign choice. One of its features was that listeners could purchase their own commercials on KADS, not unlike classified advertising in a newspaper. FM radios were still not widely owned in the 1960s and the experimental format was not successful. Beautiful music In March 1968, the station adopted the KOST-FM call sign, along with a substantially all-music format (i.e., no news bulletins), which was unusual, if not unique, given then-prevailing license obligations to broadcast at least some news. The station aired a mostly-instrumental beautiful music format. In 1973, Cox Communications purchased KOST to pair with its newly-bought KFI (640 AM). KOST, with its call sign pronounced "coast" in a stage whisper, continued its easy listening format through the 1970s. This popular format was also heard on rivals KJOI (98.7 FM) and KBIG (104.3). In the early 1980s, KOST gradually added more vocals, and on November 15, 1982, the station switched to an adult contemporary format. Former Sacramento radio personality Bryan Simmons was KOST's first host when the station signed on with its new format. On February 3, 1986, Mark Wallengren and Kim Amidon made their debut as KOST's new morning hosts.