Walton donated the station, then KFIF, in 1967 so that he could buy then-KTAN at 580, which had a fulltime license. KTAN went off the air May 1 of that year; KFIF planned to move - and change its call letters to KIKX - on May 15 but didn't actually appear to do so until June 10. KFIF/KIKX took over KTAN's former studios. KFIF's Top 40 format also made the move to KIKX. KTAN had broadcast "cosmpolitan music for adults". There's no indication when the university actually started operating 1550 but it would have been after June 10 since Walton continued to broadcast on 1550 until finally ready to switch over. The university added FM outlets somewhat later.
Due to the terrain in parts of Tucson - the northern "foothills" where FM signals go to die - it's possible that the university sees the AM station as a fill-in service. But I've not seen any explanation by Arizona Public Media.
And now a twist that just reinforces the need to preserve broadcast history.
There's no history card for 580 and the listing of actions on fccdata.org indicates that the current station at 580 was considered a new station in 1982. Going back through newspaper archives, a fuller story appears. The license was designated for hearing in 1975 over multiple issues, including a hoax presented as a news broadcast in 1974 claiming a KIKX DJ had been kidnapped, with the result that listeners started calling the Tucson police department about it. Shortly thereafter, Walton reportedly fired the employees who had been involved in the hoax. In October 1976, an FCC ALJ revoked KIKX's license. The station appealed, continuing in operation and switching to a country format in 1977. The full commission denied the appeal in May 1980. Court appeals ensured, but after an adverse appeals court ruling in July 1982, even with one judge dissenting by stating the FCC had overreacted, the station abruptly shut down on July 17 and turned in its license. By then, the station had been in the ratings basement for some time. It was estimated that the appeals cost $250,000.