Four years after classical station WCAL left the air in the Twin Cities region, its fans have committed to raise the legal costs and appeal their case to the Minnesota Court of Appeals. Save WCAL filed a brief yesterday asking the appellate court to undo St. Olaf College's sale of the station to Minnesota Public Radio, which now uses the frequency for its contemporary music service, The Current. The WCAL group, represented by attorney Michael McNabb, has had mixed results so far with its claim that the college ignored the intent of donors who kept WCAL going for 80 years. The case won some favorable comments from retiring Judge Gerald Wolf but lost in February with Judge Bernard Borene's summary judgment upholding the legality of the sale. Save WCAL's website says the group is raising funds to match a $25,000 challenge grant to pay McNabb, who said he could not undertake the appeal on a continuing pro bono basis.