RADIO / Men in the ironic mask: Robert Hanks celebrates New Year with U2, Christopher Hope, Oscar Wilde and Henry James

'NOW you haven't come all the way out here to watch TV, now have ya?' Bono cried: and you could spot immediately one of the problems of turning U2's 'Zoo TV' show into Zoo Radio (Radio 1, Friday): it's the wrong medium. 'Zoo TV' was, at least in part, meant as a satire on the video age - on the ways that television dominates people's minds, so that they confuse what is real with what they see on television - and radio can't help muffling that point. When one of the band says, 'The wonderful thing about TV is that wherever you are, whenever anything really important happens you can change channels,' there's less chance that the audience will suffer a frisson of self-recognition if they're not watching TV in the first place.

Still, that's the least of U2's problems. A much more serious obstacle to the band's satirical progress is the sense of irony they're supposed to have acquired. They've been sold a pup; what they've got - at least, what it feels like - is a carefully prepared impression of something ironic. They can do all the right gestures, make all the right noises (cue cliches about how the Gulf war was fought on video), but they don't have irony in the soul.

On the television version, recently shown on C4, a newscaster read computer-generated nonsense as if it was serious news. On radio, it felt as if the computer's spare capacity had been used, instead, to generate automatic paradoxes: 'Elvis is alive; we're dead,' Bono said. Somebody asked Larry Mullin: 'What's worst about rock 'n' roll?' Mullin answers: 'Excess.' 'What's best about rock 'n' roll?' 'Excess.'

There was no originality, no real fun here, and no ambiguity. For irony to work, you need some fleeting sense that the ironist isn't simply saying something different from what he means, but that he just might mean what he says; U2's clunkingly predictable one- liners left no room for doubt.

There wasn't much ambiguity, either, about The Gospel According to Tinkerbell (Radio 3, Friday), a talk by Christopher Hope about a visit to Euro Disneyland. Hope's gifts as a writer and as an observer of mores are unquestioned, but the job wasn't worthy of him. It's easy for a sensitive, cultured person to spot ironies crawling out of the woodwork in a theme park; the difficult thing would be to take it straight. So when Hope nodded to the strangeness of a place in France that tries to make you think you're in Mexico, or pointed out that in the films Mickey Mouse and Donald Duck were animals pretending to be people, whereas here real people pretended to be them - you wanted to say 'Yeah, yeah.'

Irony was used with more restraint, and to greater effect, in Nick McCarty's dramatisation of The Canterville Ghost (Radio 4, Thursday), Oscar Wilde's shortish story about an English ghost upset by the new American inhabitants of the stately home that he haunts. The temptation with Wilde (and writers can resist everything but temptation) is to shove in a stray epigram whenever you're stuck for a line - or when, as in this case, you need to pad out an insubstantial tale to fit a 90-minute slot. McCarty barely succumbed: 'We really have everything in common with America nowadays - except, of course, our language,' said Lord Canterville; otherwise, the time was used wisely in fleshing out Wilde's wraith, adding credible detail about his life and afterlife.

Edward Petherbridge played the spectre surprisingly straight, which was doubly effective: the central joke, that the Americans refuse to take him seriously, worked well when it seemed that he deserved better; and the glum persona made it easier to make the transition from mild farce into spiritual drama. The pure young American girl, Virginia, finds redemption for the ghost through her tears, in a sentimental-religious denouement that can be rather jarring. This version, produced by Hamish Wilson, managed the switch more easily than Wilde did, with the concentration on sin and forgiveness making it less Wilde than Greene.

The ending - pure child redeems wicked spirit - was neatly reversed by The Turn of the Screw (Radio 4, Friday), where wicked spirit corrupts pure child. It's not easy to preserve the ambiguity of James's tale in another medium - are the children haunted by real ghosts, or is it their protective governess who really oppresses them? Britten's opera ignored the problem, turning into a pretty straight contest of good and evil (largely, you guess, so that Peter Pears could play the ghostly Quint). John Tydeman's adaptation balanced expertly between the two; with Charlotte Attenborough's governess, hinting at hysterical depths, carrying the narrative. Here, at any rate, the medium matched the message.