What station was Clemens' first 20-K game on?

[Howard Glazer]

Dan Shaughnessy wrote a retrospective on Roger Clemens' April 29, 1986,
20-strikeout game in Saturday's Globe. In it, he mentions that the game
wasn't carried on "AM radio" (no call letters) because the Celtics had
priority and instead was carried on "FM" (again, no call letters). The
AM, I recall, was WRKO, but I have no idea which FM the game wound up
on. 

I remember occasional games being carried on 94.5 in the late '60s or
early '70s, and on 107.9 later on, but that was during 107.9's days as
WWEL, not as WXKS-FM. What FM was 'RKO's backup in the mid-'80s?

Howard