I remember when AM 1150 switched to all-sports in '97...before that, it was a simulcast of KIIS-FM, and even before that for a brief time, if I remember correctly...it ran its own lineup of music while complementing 102.7.
In the two weeks or so before the official launch, 1150 ran a recorded loop with Vic "the Brick" Jacobs announcing the new sports format. Part of the day, they also simulcast Dallas-Fort Worth's KLIF-AM...they were carrying the Dallas Mavericks games at the time, so on 1150, if the Mavericks were at home, we got to hear the first half-hour of each game.
This wasn't too long after the failure of KMAX-FM 107.1, who tried an a sports format for a couple of years (circa 1994-1996)...they had the Joe McDonnell-Doug Krikorian show, the Sports Gods (Dave Smith and Joey Haim, maybe the funniest and raunchiest sports-talk program of all time), Pete Rose's syndicated talk show, North Dame football, San Francisco 49ers, a back-up outlet for the Clippers (their flagship at the time was KGIL 1260), and it was also were J.T. The Brick got his first radio gig (just mere months after winning Jim Rome's Smackoff). Their biggest problem, among other things, was their signal strength beyond Downtown L.A. was piss-poor. At the time, I lived near the Crenshaw District of south Los Angeles, and I had to adjust the antenna towards the north (the station was based in Pasadena, but not sure where the transmitter was) just to get a decent signal. Also, XTRA Sports 690 was really making inroads into Los Angeles and Orange Counties, plus having a very solid lineup: Steve Mason & John Ireland, Jim Rome, The Loose Cannons (Steve Hartman & the late Chet Forte, later replaced by Bill Werndl), and Hacksaw Hamilton. 690 pretty much inherited the Sportsradio 710 audience they changed formats.