In Columbus, Ohio, PD Ric Knight has parted ways with Wilks Broadcasting-owned country WHOK-FM (95.5) "The Hawk" & WNKK-FM (107.1). No replacement has been named ... Pittsburgh's non-commercial WESA-FM (90.5) adds Paul Guggenheimer from South Dakota Public Radio for middays, and will host "Essential Pittsburgh," their weekday talk show ... Washington, DC's WTOP-FM (103.5) will lose sports contributor and former Washington Redskins star John Riggins, who will be doing more work on TV's Outdoor Channel ... Also in the Nation's Capital, former Georgetown University coach John Thompson announced he's ending his radio show on Red Zebra's WTEM-AM "ESPN" (980) in February ... Larry McKay is leaving Melbourne, Florida's CHR WAOA-FM (107.1) after about 18 months ... Envision Radio Networks adds rhythmic KVEG-FM (97.5) as an affiliate of Clairissa Jenkins' Phone Checks.