Saying he wants to reinvigorate radio on Cape Cod, longtime Boston radio personality John Garabedian has bought three rock ’n’ roll stations, including the once-popular PIXY 103. “I’m bored. It’s time to do something new,” said Garabedian, who is well known from his days at WBCN-FM (104.1), WMEX-AM (1510), and as host of the nationally syndicated “Open House Party” show. “I want to make these stations the most listened to on Cape Cod.” Garabedian, who splits his time between Southborough, Falmouth, and Cabot, Vt., bought WPXC-FM – known as PIXY 103 – and WFRQ-FM (101.1), and WFQR-FM (93.5.), and plans to upgrade all three signals. PIXY 103, which began broadcasting a mix of hits and classic rock in 1987, was previously owned by Nassau Broadcasting. But the company declared bankruptcy last year and its stations were sold at auction.