From the Chicago Sun-Times:

A George Will column argued that Public Radio could well be financed by its generally upscale listeners.
The headline in the New Hampshire Union Leader was
How the Corporation for Public Broadcasting is like the human appendix
He wrote, “The lowest of the low-hanging fruit for budget-cutters is the Corporation for Public Broadcasting, an ornamental entity, decorative but inessential.”
Will wrote that such stations and the PBS television counterparts only rely upon the Federal government for 15% of their budgets.
Listeners provide a significant part of the stations’ budgets.
WBEZ obtains 4.6% from the Corporation for Public Broadcasting.
“Public broadcasting stations are prohibited from running commercials,” the Sun-Times reports.
It is allowed “corporate underwriting spots, which are supposed to be nonpromotional announcements that acknowledge their financial support.”
The on-air sponsorships sound a lot like ads to me.
WBEZ reveals, “WBEZ received a letter on Feb. 28 from the FCC’s enforcement bureau requesting detailed information about underwriting announcements that air on the station, giving it 30 days to respond.”
WBEZ said it will reply in a timely fashion.