Hmmmm. I only recently 'discovered' C-Span at all. From time to time I check it and sometimes there is someone (usually selling a book) giving a talk on a certain subject in a setting like in a library or some such and there are maybe 40 people listening and asking questions.

Many of those shows I enjoy a lot, and sometimes I jot down the name of a book I want to order when it comes out.

But I guess I'm not checking it often enough to ever come upon a radio talk show. At least I haven't come across one yet. And I wouldn't linger if I did.