The metro Detroit area\'s three university-affiliated public radio stations finished their spring pledge periods this month with a mixed bag. Wayne State University\'s WDET-FM (101.9) reported raising about $600,000 in the spring but said before the campaign the goal was $800,000. In the spring, WDET said it raised about $200,000 in a pre-pledge effort, which it said was a 95-percent increase over the pre-pledge campaign of the troubled fall fund-raiser. About 6,400 listeners have made a pledge; around 2,000 of those donating to WDET have done so for the first time.