Vanishing subsidies and harder-to-get donations prompted an audience examination at WDET 101.9 FM, leading to several program changes. For a public radio station that gets 62 percent of its $3.8 million budget from individual donations, that was a problem that had to be fixed, said General Manager Caryn Mathes. \"Public stations have to be aware of the time spent listening because that relates directly to giving,\" Mathes said. \"If we see we\'re reaching diminished numbers of people, the cost of a show becomes critical.\"