sentences:  Ratings crashed to a 0.9 share in the summer of 1986 Arbitron, under the new call sign WKTH.In 1988, the station adopted Satellite Music Network's Z-Rock format, keeping the WKTH call letters.The station reverted to the WGRD calls in 1991, moving back to a simulcast of 97.9 FM's CHR format (which changed to Modern Rock in 1994).