A search for renewal was done in publications for the years 1961 (part 1), 1961 (part 2), 1962 (part 1) and 1962 (part 2). There were no listings for the title Radio Stars. There's no evidence of renewal for the magazine.
Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (70 years p.m.a.), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties.