Radio: The Summer Shows

Medallion Theater (Sat. 10 p.m., CBS-TV) is a potentially first-rate summer series that, so far, has had trouble getting off the ground. The first program was a painstaking, rather flat dramatization of an episode from Sinclair Lewis' Arrowsmith. Others have included The Man Who Liked Dickens, starring Claude Rains, a prettied-up version of Evelyn Waugh's story of a lost explorer held captive by an illiterate half-breed, and Mrs. Union Station, a farce starring June Havoc. The show may have better luck this week with Charles Ruggles in an adaptation of Richard Harding Davis' The Consul. The commercials plug a different Chrysler Corp. car each week.

First Person (Fri. 8:30 p.m., NBCTV) often uses the camera as one of its actors, and leans toward old-fashioned horror stories. Last week's show was a supernatural melodrama about a numbed victim and a reluctant murderer, but toward the end, the eerie quality dissolved into unexplained silliness. Sponsor: Gulf Oil.

21st Precinct (Tues. 9:30 p.m., CBS Radio) makes an effective half-hour of police drama (from Manhattan files), but loses a lot of sting from its resemblance to NBC's Dragnet (from Los Angeles iles). In its favor, the new show has Actors Everett Sloane and Joan Lorring and Director-Writer Stanley (Gangbusters) Niss, an expert at creating minor personalities. 21st Precinct captures the sounds and scenes of everyday police work; the characters are all underplayed, just like Dragnet (which pretty much originated that school of radio acting, and has lately begun underplaying its own underplaying). Unsponsored.