CANADA HAS NEVER really had a national theatre. Blame it on our tiny population scattered from sea to sea, the schism of having two official (and many unofficial) languages, or the decision to locate the national capital in Bytown; the fact remains that even if we could agree that we wanted a national theatre, it would be hard to imagine ever reaching consensus on where to put it. Yet where better to locate it than in the imagination? Radio, by virtue of being nowhere, can be everywhere at once, and the members of its audience are united by their isolation. Indeed, radio drama in this country was such a national theatre for several decades around the middle of this century, before live theatre prospered as a preferable forum for serious writing and television robbed radio of its audience. For 20 or 30 years, radio drama was out of fashion. I confess that I tuned in to it rarely, and when I did it struck me as one of the creakier forms of entertainment, still mired somewhere in the last century. And yet, in recent years, as live theatre flounders for lack of funds and TV no longer bothers to pretend its purpose is any higher than selling audiences to advertisers, radio has provided a welcome outlet for dramatic writing. The CBC produces about 150 radio dramas a year, ranging from the hour-long AM "Sunday Matinee" and FM "Stereo Theatre" to the late- evening head-trippy "Vanishing Point" series and the more conventional Monday-to-Friday 15-minute episodes on "Morningside," which reach a national audience of close to three-quarters of a million people. What stage playwright would dare dream of such numbers? Greg Sinclair, who produces and directs radio drama for the CBC, woos playwrights by drawing their attention "to the fact that radio drama exists and can serve their needs as writers." More and more of them are becoming interested, and Sinclair credits this "groundswell of interest" to active solicitation by radio producers -- solicitation that is necessary, he acknowledges, because radio drama's reputation among artists is not high. David Demchuck, author of Alaska (which was recently broadcast on "Morningside") remembered tuning in to CBC radio and thinking, "My God, my cat could write that!" Sinclair agrees that the CBC's demand for hundreds of radio dramas a year has at times exceeded the supply of quality material, and laments the fact that when playwrights do finally consider radio they may just reach into their proverbial bottom drawer, as if any old discarded script would be good enough for resurrection on radio. But "it's a medium that is dramatically unforgiving," Sinclair insists. Since there are no stage effects or visuals to fall back on, character, plot, and language have to work. If anything, writing for radio must be of higher quality than dramatic writing for stage or TV. Yet, in spite of its difficulties and disadvantages, writers find radio drama has unique rewards. Carol Bolt, a veteran stage and television writer, initially turned to radio because several of her ideas for plays were too expensive for either stage or TV (requiring many set changes and huge numbers of characters). She continues to write for radio because, as she comments, "Radio is the only medium where you continually get really personal letters back." That special, intimate connection with the audience is important, but radio has other advantages, too. Robyn Marie Butt, whose first radio drama, Queenie's History of the World, aired on "Sunday Matinee" in February, prefers radio to television, because "in TV, the writer is a nobody, a creative typist. In radio, they treat you like an artist." David Demchuck agrees. In radio, he says, the writer is the focus, since "it really does live and die on the script." He also appreciates the fact that the medium allows a playwright to reach "an audience that would never otherwise get anywhere near your work." His drama, Alaska, was the first radio drama to deal with AIDS, and he saw the challenge of writing for such a huge mainstream audience in terms of "How explicit can I be?" Demchuck also notes that EnglishCanadian playwriting has always been based on a literary rather than a visual tradition. Internationally, such writers as Tom Stoppard, Harold Pinter, and the late Samuel Beckett have contributed some of their best work to radio. Respected Canadian playwrights, like Judith Thompson, Don Hannah, and Joan MacLeod, have begun to do so too. Perhaps radio drama in this country is on its way to becoming, once again, our national theatre.