PBS is funded indirectly by Congress through the Corporation for Public Broadcasting (CPB; which funds both PBS and National Public Radio). For fiscal year 2010, $281m out of CPB's $422m appropriation went to public television, $210m to local stations and $71m to PBS directly (
http://en.wikipedia.org/wiki/Pub...). In 2010, PBS had revenues of around $570m (
http://www.pbs.org/about/media/a...), meaning federal funding via CPB accounted for about 12% of PBS 2010 annual revenues. Note that some of that federal funding for local stations will also make it back indirectly to PBS in the form of programming fees, so the total percentage could be considered higher.