In this time of unprecedented threat to public broadcasting, people are responding with unprecedented generosity to station’s pleas for support. TV station WPBA in Atlanta beat its $75,000 pledging goal by 39 percent, with pitching help from hometown boy Newt Gingrich. The boon fell just short of doubling WPBA’s in-take during last year’s March drive — $42,000. If donations to the system expand permanently by 15 percent, the increase would amount to about $58.5 million — one-fifth of this year’s federal appropriation to CPB. Pacifica station WBAI in New York broke a record for community radio stations with an $820,000 January drive.